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Journal of Inorganic Biochemistry

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ISSN (Print) 0162-0134
Published by Elsevier

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Second- and higher-order structural changes of DNA induced by antitumor-active tetrazolato-bridged dinuclear platinum(II) complexes with different types of 5-substituent
- Abstract: Publication date: Available online 9 May 2013
  Source:Journal of Inorganic Biochemistry
  Author(s): Masako Uemura , Yuko Yoshikawa , Kenichi Yoshikawa , Sato Takaji , Yoshiki Mino , Masahiko Chikuma , Seiji Komeda
  Here, we used circular dichroism (CD) and fluorescence microscopy (FM) to examine the interactions of a series of antitumor-active tetrazolato-bridged dinuclear platinum(II) complexes, [{cis-Pt(NH3)2}2(μ-OH)(μ-5-R-tetrazolato-N2,N3)]n+ (R = CH3 (1), C6H5 (2), CH2COOCH2CH3 (3), CH2COO− (4), n = 2 (1−3) or 1 (4)), which are derivatives of [{cis-Pt(NH3)2}2(μ-OH)(μ-tetrazolato-N2,N3)]2+ (5-H-Y), with DNA to elucidate the influence of these interactions on the secondary or higher-order structure of DNA and reveal the mechanism of action. The CD study showed that three derivatives, 1−3, with a double-positive charge altered the secondary structures of calf thymus DNA but that 4, the only complex with a single positive charge, induced almost no change, implying that the B- to C-form conformational change is influenced by ionic attraction. Unexpectedly, single-molecule observations with FM revealed that 4 changed the higher-order structure of T4 DNA into the compact-globule state most efficiently, at the lowest concentration, which was nearly equal to that of 5-H-Y. These contradictory results suggest that secondary structural changes are not necessarily linked to higher-order ones, and that the non-coordinative interaction could be divided into two distinct interactions: (1) ionic attraction and (2) hydrogen bonding and/or van der Waals contact. The relationship between diffusion-controlled non-coordinative DNA interactions and cytotoxicities are also discussed.
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  PubDate: 2013-05-11T16:26:54Z
The extracellular loop of IRT1 ZIP protein - the chosen one for zinc'
- Abstract: Publication date: Available online 6 May 2013
  Source:Journal of Inorganic Biochemistry
  Author(s): Slawomir Potocki , Daniela Valensin , Francesca Camponeschi , Henryk Kozlowski
  Zinc complexes with the extracellular loop of IRT1 (iron-regulated transporter 1), a ZIP (ZRT/IRT – Related Protein) family protein from Arabidopsis thaliana , has been studied. This unstructured fragment is responsible for metal selectivity and is located between the II and III transmembrane domains of IRT1. Zinc complexes with the Ac-(95)MHVLPDSFEMLSSICLEENPWHK(117)-NH2 peptide (IRT1), revealed surprisingly high thermodynamic stability. Additionally, an N-terminal fragment of human/mouse ZIP 13 zinc transporter (MPGCPCPGCGMACPR-NH2, later called ZIP13+C), has been chosen for the thermodynamic stability comparison studies. The relative ZIP13+C stability has been shown using several Zn2+ complexes with artificially arranged multi-cysteine sequences. An interesting coordination mode has been proposed for the IRT1 - Zn2+ complex, in which imidazoles from two histidines (His-96 and His-116), a cysteine thiolate (Cys-109) and one of a glutamic acid carboxyl group are involved. All data were collected using potentiometric, NMR and mass spectrometric methods.
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  PubDate: 2013-05-08T16:25:04Z
Solution Equilibria of Anticancer Ruthenium(II)-(η6-p-Cymene)-Hydroxy(thio)pyr(id)one Complexes: Impact of Sulfur vs. Oxygen Donor Systems on the Speciation and Bioactivity
- Abstract: Publication date: Available online 7 May 2013
  Source:Journal of Inorganic Biochemistry
  Author(s): Éva A. Enyedy , Éva Sija , Tamás Jakusch , Christian G. Hartinger , Wolfgang Kandioller , Bernhard K. Keppler , Tamás Kiss
  Stoichiometry and stability of antitumor ruthenium(II)−η6-p-cymene complexes of bidentate (O,O) hydroxypyrone and (O,S) hydroxythiopyr(id)one type ligands were determined by pH-potentiometry, 1H NMR spectroscopy and UV−Vis spectrophotometry in aqueous solution and in dependence of chloride ion concentration. Formation of mono-ligand complexes with moderate stability was found in the case of the hydroxypyrone ligands (ethyl maltol and allomaltol) predominating at the physiological pH range. These complexes decompose to the dinuclear tri-hydroxido bridged species [{RuII(η6-p-cymene}2(OH)3]+ and to the metal-free ligand at basic pH values. In addition, formation of a hydroxido [RuII(η6-p-cymene)(L)(OH)] species was found. The hydroxythiopyr(id)one ligands (thiomaltol, thioallomaltol, 3-hydroxy-1,2-dimethyl-thiopyridone) form complexes of significantly higher stability compared with the hydroxypyrones; their complexes are biologically more active, the simultaneous bi- and monodentate coordination of the ligands in the bis complexes (ML2 and ML2H) was also demonstrated. In the case of thiomaltol, formation of tris complexes is also likely at high pH. The replacement of the chlorido by the aqua ligand in the [RuII(η6-p-cymene)(L)(Cl)] species was monitored, which is an important activation step in the course of the mode of action of the complexes, facilitating binding to biological targets.
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  PubDate: 2013-05-08T16:25:04Z
Copper(II) mixed chelate compounds induce apoptosis through reactive oxygen species in neuroblastoma cell line CHP-212
- Abstract: Publication date: Available online 7 May 2013
  Source:Journal of Inorganic Biochemistry
  Author(s): Anllely Grizett Gutiérrez , Adriana Vázquez-Aguirre , Juan Carlos García-Ramos , Marcos Flores-Alamo , Enrique Hernández-Lemus , Lena Ruiz-Azuara , Carmen Mejía
  In the present work we report the antiproliferative activity of Cu(II) coordination compounds, CasIIgly ([Cu(4,7-dimethyl-1,10-phenanthroline) (glycinato) (H2O)]NO3), CasIIIia ([Cu(4,4'-dimethyl-2,2'-bipyridine) (glycinato) (H2O)]NO3), and CasIIIEa ([Cu(4,7-dimethyl-1,10-phenanthroline) (acetylacetonato) (H2O)]NO3), against human tumoral cell line CHP-212 (estromal neuroblastoma). Additionally, the molecular structure of CasIIIEa was reported. The IC50 values obtained for the evaluated compounds are in the range 18 to 47μM, representing an inhibition potency increase of 5 to 12 times compared with cisplatin (IC50 =226.7μM). After 2h of incubation with the evaluated compounds, cells showed high levels of reactive oxygen species and a considerable GSH depletion, besides an important disruption of the mitochondrial membrane with release of cytochrome C and besides the presence of caspase-3, an effector caspase that is activated in the last step of apoptosis cascade. The results confirm that cell death in neuroblastoma CHP-212 treated with Casiopeínas occurs via apoptosis. Due the lack of expression of caspase-8, cell death is principally by the mitochondrial pathway. Thus, one of the most interesting findings of this work is the identification of a very important damage in neuroblastoma cells induced by Cu(II) coordination compounds in a very short exposition times.
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  PubDate: 2013-05-08T16:25:04Z
Editorial Board
- Abstract: Publication date: June 2013
  Source:Journal of Inorganic Biochemistry, Volume 123
  
  PubDate: 2013-05-05T16:29:57Z
Contents
- Abstract: Publication date: June 2013
  Source:Journal of Inorganic Biochemistry, Volume 123
  
  PubDate: 2013-05-05T16:29:57Z
Erratum to “Lessons on the critical interplay between zinc binding and protein structure and dynamics” [JIB 121C (2013) 145–155]
- Abstract: Publication date: June 2013
  Source:Journal of Inorganic Biochemistry, Volume 123
  Author(s): Claudia A. Blindauer
  
  PubDate: 2013-05-05T16:29:57Z
Can the local enzyme scaffold act as an H-donor for a Co(I)--H bond formation' The curious case of Methionine Synthase-bound cob(I)alamin
- Abstract: Publication date: Available online 30 April 2013
  Source:Journal of Inorganic Biochemistry
  Author(s): Manoj Kumar , Pawel M. Kozlowski
  The density functional calculations and analysis of the existing X-ray crystallographic data have been carried out to gain mechanistic insight into the reactivation cycle of methionine synthase (MetH) enzyme. The calculations were carried out on the cobinamide-type model complexes of cob(I)alamin (Co(I)Cbx) testing H2O and PhOH as possible β-axial ligands. The PhOH motif was used to mimick the tyrosine (Y1139) residue that has been found in the active site of the MetH-bound cob(II)alamin (Co(II)Cbx). The calculations indicate that the β-axial PhOH ligand forms stronger Co(I)--H bonds than H2O ligand due to its better H-donor capacity. The calculated redox impact of Co(I)--H interactions on the reduction potential of Co(II)/Co(I) couple (60-800 mV vs standard hydrogen electrode (SHE)), irrespective of the β-axial ligand considered, is significantly higher than the biological redox gap between the reduction potential of Co(II)/Co(I) couple and that of the biological reducing agents (50 mV vs SHE). The analysis of existing crystallographic data for the reactivation conformation of MetH enzyme (1K7Y (@3.0 Å); 1K98 (@3.8 Å) and 3IVA (@2.7 Å)) indicate that the Y1139 residue and the β-axial H2O ligand in the MetH-bound Co(II)Cbx complex are equidistant from the Co(II) ion (Y1139--Co(II) = 3.97 Å; H2O--Co(II) = 3.96 Å). Taking into account that the Y1139-induced Co(I)--H linkages are thermodynamically more stable than the H2O-induced ones, the present calculations suggest that the Y1139 residue may serve as the β-axial ligand in the reactivation conformation of MetH enzyme.
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  PubDate: 2013-05-02T19:59:24Z
Synthesis, properties, and antitumor effects of a new mixed phosphine gold(I) compound in human colon cancer cells
- Abstract: Publication date: July 2013
  Source:Journal of Inorganic Biochemistry, Volume 124
  Author(s): Giulio Lupidi , Luca Avenali , Massimo Bramucci , Luana Quassinti , Riccardo Pettinari , Hala K. Khalife , Hala Gali-Muhtasib , Fabio Marchetti , Claudio Pettinari
  The antineoplastic potential of a new stable mixed phosphine gold(I) complex containing tris(tert-butyl)phosphine (tBu3P) and bis(diphenylphosphino)ethene (dppet), namely [Au(tBu3P)(dppet)Cl], has been investigated in the human colon cancer HCT-116 cell line. The 31P NMR solution study, confirms the structural features observed in the solid state and, in addition, indicates partial formation of dinuclear cationic [Au(tBu3P)2]+ and [Au(dppet)2]+ species. The ionic character and strong Au–P bonds of this gold(I) species are similar to those of the most active antitumor gold compounds so far studied. The title compound was found to exhibit strong cytotoxicity, showing 85 fold greater toxicity than cisplatin (IC50 =0.45μM vs IC50 =39.16 for cisplatin at 24h) on the HCT-116 line. The cytotoxic effects were, at least partly, mediated by the induction of apoptotic cell death as evidenced by the sub-G1 cell accumulation, oligonucleosomal DNA fragmentation, caspase-3 activation and the release of cytochrome c from the mitochondria. The gold(I) compound showed little interaction with DNA measured through fluorescence quenching studies with calf thymus DNA. The inhibitory effect of the gold(I) compound on intracellular redox proteins has been also observed in pretreated HCT-116 cells. The compound was particularly effective in inhibiting thioredoxin reductase, that is likely responsible for the increased ROS production, and subsequent apoptosis induction via the mitochondrial pathway.
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  PubDate: 2013-04-29T16:32:26Z
Comparative study of reaction of cobalamin and cobinamide with thiocyanate
- Abstract: Publication date: Available online 28 April 2013
  Source:Journal of Inorganic Biochemistry
  Author(s): Ilia A. Dereven’kov , Denis S. Salnikov , Sergei V. Makarov , Mihai Surducan , Radu Silaghi-Dumitrescu , Gerry R. Boss
  The interaction of Co(III) and Co(II) cobalamin (Cbl) and cobinamide (Cbi) with thiocyanate was examined with UV-vis and EPR spectra. S/N-linkage isomerism was explored on Co(III) and Co(II) Cbl and Cbi models using Density Functional Theory (DFT; BP86, B3LYP). Performed calculations suggest the prevalence of isothiocyanato isomers over thiocyanato complexes on both Co(III) and Co(II) centers. The formation of Cbl(II) complex with thiocyanate was observed at high ligand concentrations which was proposed to be hexacoordinated. DFT data maintain the possibility of hexacoordinated Co(II) complexes with thiocyanate in which one of extra-ligands is weakly coordinated. It is found that high thiocyanate concentrations could retard cyanide binding to cobalamin but not to cobinamide.
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  PubDate: 2013-04-29T16:32:26Z
Molecular mechanisms of the biological activity of the anticancer drug elesclomol and its complexes with Cu(II), Ni(II) and Pt(II)
- Abstract: Publication date: Available online 28 April 2013
  Source:Journal of Inorganic Biochemistry
  Author(s): Arun A. Yadav , Daywin Patel , Xing Wu , Brian B. Hasinoff
  The bis(thiohydrazide) amide elesclomol has extremely potent antiproliferative activity and is currently in clinical trials as an anticancer agent. Elesclomol strongly binds copper and may be exerting its cell growth inhibitory effects by generating copper-mediated oxidative stress. Nickel(II) and platinum(II) complexes of elesclomol were synthesized and characterized in order to investigate if these biologically redox inactive metal complexes could also inhibit cell growth. The nickel(II)-elesclomol and platinum(II) elesclomol complexes were 34- and 1040-fold less potent than the copper(II)-elesclomol complex towards human leukemia K562 cells. These results support the conclusion that a redox active metal is required for elesclomol to exert its cell growth inhibitory activity. Copper(II)-elesclomol was also shown to efficiently oxidize ascorbic acid at physiological ascorbic acid concentrations. Reoxidation of the copper(I) thus produced would lead to production of damaging reactive oxygen species. An X-ray crystallographic structure determination of copper(II)-elesclomol showed that it formed a 1:1 neutral complex with a distorted square planar structure. The kinetics and equilibria of the competition reaction of the strong copper(II) chelator TRIEN with copper(II)-elesclomol were studied spectrophotometrically under physiological conditions. These results showed that elesclomol bound copper(II) with a conditional stability constant 24-fold larger than TRIEN. A log stability constant of 24.2 was thus indirectly determined for the copper(II)-elesclomol complex.
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  PubDate: 2013-04-29T16:32:26Z
Pro-oxidant properties of indolone-N-oxides in relation to their antimalarial properties
- Abstract: Publication date: Available online 29 April 2013
  Source:Journal of Inorganic Biochemistry
  Author(s): Nguyen Thi Hoang Yen , Hany Ibrahim , Karine Reybier , Pierre Perio , Florence Souard , Ennaji Najahi , Paul-Louis Fabre , Francoise Nepveu
  Indolone-N-oxides (INODs) are bioreducible and possess remarkable anti-malarial activities in the low nanomolar range in vitro against different Plasmodium falciparum (P. falciparum) strains and in vivo. INODs have an original mechanism of action: they damage the host cell membrane without affecting non-parasitized erythrocytes. These molecules produce a redox signal which activates SYK tyrosine kinases and induces a hyperphosphorylation of AE1 (band 3, erythrocyte membrane protein). The present work aimed to understand the early stages of the biochemical interactions of these compounds with some erythrocyte components from which the redox signal could originate. The interactions were studied in a biomimetic model and compared with those of chloroquine and artemisinin. The results showed that INODs i) do not enter the coordination sphere of the metal in the heme iron complex as does chloroquine; ii) do not generate iron-dependent radicals as does artemisinin; iii) generate stable free radical adducts after reduction at one electron; iv) cannot trap free radicals after reduction. These results confirm that the bioactivity of INODs does not lie in their spin-trapping properties but rather in their pro-oxidant character. This property may be the initiator of the redox signal which activates SYK tyrosine kinases.
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  PubDate: 2013-04-29T16:32:26Z
the second generation of Iodido complexes: trans-[PtI2(amine)(amine´)] bearing different aliphatic amines
- Abstract: Publication date: Available online 28 April 2013
  Source:Journal of Inorganic Biochemistry
  Author(s): Thalia Parro , María Angeles Medrano , Leticia Cubo , Sandra Muñoz-Galván , Amancio Carnero , Carmen Navarro-Ranninger , Adoración G. Quiroga
  The antitumoral potential for a series of platinum iodido complexes, all bearing the same aliphatic amines (first iodido complexes generation), was demonstrated in a previous study. Concretely, cis complexes were shown to have a peculiar and different reactivity compared to cisplatin with sulphur donors models and Cyt C. In this work we have synthesized and studied iodido complexes bearing different aliphatic amines in trans configuration (the second generation) to investigate their potential antitumor activity in a panel of cell lines. Their interaction with biological models such as pBR322 and smaller biomolecules (5’-GMP, 9EtG, N-AcMet and N-AcCys) have been studied and compared to cisplatin and to the first iodido series. Their cytotoxicity, on the other hand, turned out to be especially active towards cell lines where cisplatin has no effect.
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  PubDate: 2013-04-29T16:32:26Z
Synthesis, chemical characterization and biological activity of new histone acetylation/deacetylation specific inhibitors: A novel and potential approach to cancer therapy
- Abstract: Publication date: Available online 25 April 2013
  Source:Journal of Inorganic Biochemistry
  Author(s): Ornella Pellerito , Cristina Prinzivalli , Elisabetta Foresti , Piera Sabatino , Michele Abbate , Girolamo Casella , Tiziana Fiore , Michelangelo Scopelliti , Claudia Pellerito , Michela Giuliano , Giulia Grasso , Lorenzo Pellerito
  Three new triorganotin(IV) complexes of valproic acid (vp1, Me3Sn-valproate; vp2, Bu3Sn-valproate; vp3, Ph3Sn-valproate) have been synthesized and investigated by spectroscopic and biological methods. An anionic, monodentate valproate ligand was observed, ester-like coordinating the tin atom on a tetra-coordinated, monomeric environment. The structures, though, can distort towards a penta-coordination, as a consequence of a long range O···Sn interaction. Crystallographic and NMR findings confirm this situation both in solid state and solution. Biological finding evidenced a clear cytotoxic action of the complexes in hepatocellular carcinoma cell cultures: one of the complexes induced an 80% cell viability reduction after 24 h treatment in HepG2 cells. This effect was accompanied by the appearance of biochemical signs of apoptosis. In Chang liver cells, the same compound induced only modest effects, suggesting a potential use as anti-cancer drug. Preliminary evaluations on hyperacetylation state of histone H3 in tributyltin-valproate treated HepG2 cells showed an increase in Ac-H3 (histone H3 acetylated at lys-9 and lys-14), suggesting that the compound maintains the deacetylation inhibition activity of its ligand valproate.
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  PubDate: 2013-04-26T16:04:17Z
Dinuclear and heptanuclear complexes of copper(II) with 7-azaindole ligand: Synthesis, characterization, magnetic properties, and biological activity
- Abstract: Publication date: Available online 24 April 2013
  Source:Journal of Inorganic Biochemistry
  Author(s): Jacob A. Przyojski , Nicole N. Myers , Hadi D. Arman , Andrey Prosvirin , Kim R. Dunbar , Mohan Natarajan , Manickam Krishnan , Sumathy Mohan , Judith A. Walmsley
  Three new complexes of Cu(II) with 7-azaindole have been synthesized and characterized, a dicopper compound, [Cu(C7H5N2)2(H2O)]2·2CH3CN, 1, and two heptacopper compounds [Cu7(C7H5N2)6(μ3-OH)6(μ2-H2O)2(μ2-CH3OH)4](CH3COO)2·2C7H8·6 CH3OH , 2, and [Cu7(C7H5N2)5(CH3COO) (μ3-OH)6(μ2-H2O)4(μ2-CH3OH)2](CH3COO)2 , 4. The structure of 2 is monoclinic and it crystallizes in the P21/C space group: a=13.475(4) Å; b=12.945(4) Å; c=23.392(7) Å; β=91.232(6)o. It contains a unique Cu7O12 core in which a central Cu(II) is situated at an inversion center and is bonded to 6 other Cu(II) ions via bridging oxygen atoms from OH-, H2O, and CH3OH groups. Anionic 7-azaindole ligands bridge between adjacent outer Cu(II) ions and all Cu(II) ions have distorted octahedral coordination geometries. Variable temperature magnetic susceptibility measurements revealed the presence of antiferromagnetic exchange interactions between Cu(II) ions which leads to an S = 5/2 ground state at 1.8 K. Cytotoxicity and cell proliferation activities of the Cu compounds using human tongue squamous cell carcinoma and normal cells revealed that the compounds stimulated proliferation in both types of cells.
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  PubDate: 2013-04-26T16:04:17Z
Two copper complexes from two novel naphthalene-sulfonyl-triazole ligands: different nuclearity and different DNA binding and cleavage capabilities
- Abstract: Publication date: Available online 24 April 2013
  Source:Journal of Inorganic Biochemistry
  Author(s): Javier Hernández-Gil , Sacramento Ferrer , Nuria Cabedo , María Pilar López-Gresa , Alfonso Castiñeiras , Francesc Lloret
  Two novel naphthalene-sulfonyl-triazole ligands, 5-amino-N1-(naphthalen-3-ylsulfonyl)-1,2,4-triazole (anstrz) and 3,5-diamino-N1-(naphthalen-3-ylsulfonyl)-1,2,4-triazole (danstrz), purposely designed to interact with DNA, have been prepared for the first time and then fully characterized by 1H, 13C NMR, and IR spectroscopy, mass spectrometry and elemental analysis. The crystal structures of two copper complexes of these derivatives, i.e. [Cu(anstrz)4(NO3)2]∙4CH3OH (1), mononuclear, and [Cu(danstrz)(μ-OAc)2]2∙2(danstrz) (OAc = acetato) (2), dinuclear, have been determined by single-crystal X-ray diffraction. In both cases the ligand coordinates in a monodentate fashion via the N4 nitrogen atom of the triazole ring. Compound 2, an example of paddle wheel type copper acetate, presents a Cu···Cu’ distance of 2.667(1) Å. As a result of strong stacking interactions and intense H-bonds, the structure of 2 constitutes a MOF (metal-organic framework). Besides, this dinuclear compound exhibits a very strong antiferromagnetic coupling (J = −324 cm−1) and a silent X-band EPR at room temperature. The affinity toward DNA of 1 and 2 has been examined by fluorescence emission spectroscopy, thermal denaturation and viscosimetry assays. The apparent binding constant (K app) values of 2.2×107 M−1 for 1 and 2.6×107 M−1 for 2 suggest important DNA interaction. The dinuclear compound (2) intercalates and produces a high change in the T m. Both compounds promote DNA scission in the presence of H2O2/ascorbate (1) or ascorbate (2) through oxidative mechanism. The possible reasons for the higher DNA affinity and the more efficient DNA cleavage displayed by compound 2 in relation to compound 1 are discussed.
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  PubDate: 2013-04-26T16:04:17Z
Palladium(II) and platinum(II) bis(thiosemicarbazone) complexes of the 2,6-diacetylpyridine series with high cytotoxic activity in cisplatin resistant A2780cisR tumor cells and reduced toxicity
- Abstract: Publication date: Available online 23 April 2013
  Source:Journal of Inorganic Biochemistry
  Author(s): Ana I. Matesanz , Inés Leitao , Pilar Souza
  Preparation and characterization of four novel 2,6-diacetylpyridine bis(4 N-tolyl thiosemicarbazonato) palladium(II) and platinum(II) complexes, [PdL1-2] and [PtL1-2], is described. All compounds have been characterized by elemental analysis and by IR and NMR spectroscopy, and the crystal and molecular structures of complexes [PdL2] and [PtL2] have been determined by single crystal X-ray diffraction. The ligands act as dianionic tetradentate donors coordinating to the metal center in a square planar geometry through the Npyridinic atom and the Niminic and the S atoms from one thiosemicarbazone arm, the fourth coordination position is occupied by the Nhydrazinic of the other arm. The new compounds synthesized have been evaluated for antiproliferative activity in vitro against NCI-H460, HepG2, MCF-7, A2780 and A2780cisR human cancer cell lines. The cytotoxicity data suggest that [PdL1], [PdL2] and [PtL2] may be endowed with important antitumor properties since they are capable of not only circumvent cisplatin resistance in A2780cisR cells but also exhibit high antiproliferative activity in breast cancer MCF-7 cells. Subsequent toxicity study, in LLC-PK1 cells, has also been carried out and shows that none of these compounds are in vitro toxic in the tested concentration range.
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  PubDate: 2013-04-23T16:25:54Z
Bio-inspired citrate-functionalized apatite thin films crystallized on Ti-6Al-4V implants pre-coated with corrosion resistant layers
- Abstract: Publication date: Available online 18 April 2013
  Source:Journal of Inorganic Biochemistry
  Author(s): José Manuel Delgado-López , Michele Iafisco , Isaac Rodríguez-Ruiz , Jaime Gómez-Morales
  In this paper the crystallization of a bioinspired citrate-functionalized apatite (cit-Ap) thin film (thickness about 2μm) on Ti-6Al-4V supports pre-coated with bioactive and corrosion resistant buffer layer of silicon nitride (Si3N4), silicon carbide (SiC) or titanium nitride (TiN) is reported. The apatitic coatings were produced by a new coating technique based on the induction heating of the implants immersed in a flowing calcium-citrate-phosphate solution at pH11. The influence of the buffer layers and the surface roughness of the substrate on the chemical-physical features and adhesion of the cit-Ap films were investigated. The best plasticity, compactness and adherence properties have been found in the Ap layer grown on Si3N4, followed by the Ap grown on SiC and TiN, respectively. The adhesion property was likely related to the roughness of the buffered substrates, whereas the compactness and plasticity were closely related to the operating conditions during the Ap crystallization (flow rate of the solution and increase of temperature) rather than to the nature of the buffer layer.
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  PubDate: 2013-04-20T16:22:30Z
A novel platinum complex of the histone deacetylase inhibitor belinostat: Rational design, development and in vitro cytotoxicity
- Abstract: Publication date: July 2013
  Source:Journal of Inorganic Biochemistry, Volume 124
  Author(s): James P. Parker , Hassan Nimir , Darren M. Griffith , Brian Duff , Anthony J. Chubb , Marian P. Brennan , Maria P. Morgan , Denise A. Egan , Celine J. Marmion
  The successful design and synthesis of a novel Pt complex of the histone deacteylase inhibitor belinostat are reported. Molecular modelling assisted in the identification of a suitable malonate derivative of belinostat (mal-p-Bel) for complexation to platinum. Reaction of [Pt(NH3)2(H2O)2](NO3)2 with the disodium salt of mal-p-Bel gave cis-[Pt(NH3)2(mal-p-Bel-2H)] (where -2H indicates that mal-p-Bel is doubly deprotonated) in excellent yield. An in vitro cytotoxicity study revealed that cis-[Pt(NH3)2(mal-p-Bel-2H)] possesses (i) considerable cytotoxicity against reported ovarian cancer cell lines, (ii) enhanced cytotoxicity relative to the previously reported Pt histone deacetylase inhibitor conjugate, cis-[PtII(NH3)2(malSAHA-2H)] and (iii) favourable cyto-selective properties as compared to cisplatin and belinostat.
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  PubDate: 2013-04-20T16:22:30Z
Kinetics and mechanism of reactions of the drug tiopronin with platinum(IV) complexes
- Abstract: Publication date: Available online 19 April 2013
  Source:Journal of Inorganic Biochemistry
  Author(s): Shuying Huo , Hongmei Shi , Dongzhi Liu , Shigang Shen , Jiong Zhang , Changying Song , Tiesheng Shi
  Tiopronin, a synthetic thiol-containing drug being used in treatments of cystinuria and certain types of rare arthritis, is also a hepatoprotective and a detoxifying agent. Many analytical methods have been developed based on its redox chemistry with metal ions/complexes, but the kinetic and mechanistic aspects are poorly understood. In this work, the oxidation of tiopronin by cisplatin prodrug and a model compound, cis-[Pt(NH3)2Cl4] and trans-[PtCl2(CN)4]2–, was investigated. The oxidation kinetics was followed by a stopped-flow spectrophotometer over a wide pH range under the pseudo first-order conditions of [Tiopronin] >>[Pt(IV)]. Time-resolved spectra were also recorded for both Pt(IV) complexes, enabling to establish an overall second-order rate law: -d[Pt(IV]/dt= k′[Tiopronin][Pt(IV)], where k′ pertains to observed second-order rate constants. Under the kinetic conditions, tiopronin was oxidized to form the tiopronin-disulfide exclusively as identified by mass spectrometry. A reaction mechanism was proposed, involving parallel reductions of the Pt(IV) complexes by the three protolytic tiopronin species as rate-determining steps. The rate constants for the rate-determining steps were derived. The fully deprotonated tiopronin is about 4 x 104 more reactive than its corresponding thiol form for both Pt(IV) complex; the huge reactivity difference orchestrates closely with the fact that the nucleophilicity of thiolate is much higher than the corresponding thiol. Hence, the attack of the sulfur atom in thiol/thiolate of tiopronin on the axially-coordinated chloride in the Pt(IV) complexes is nucleophilic in nature in the rate-determining steps, resulting in a bridge formation and a subsequent bridged electron-transfer.
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  PubDate: 2013-04-20T16:22:30Z
Metal toxicity and opportunistic binding of Pb2+ in proteins
- Abstract: Publication date: Available online 19 April 2013
  Source:Journal of Inorganic Biochemistry
  Author(s): Michael Kirberger , Hing C. Wong , Jie Jiang , Jenny J. Yang
  Lead toxicity is associated with various human diseases. While Ca2+ binding proteins such as calmodulin (CaM) are often reported to be molecular targets for Pb2+-binding and lead toxicity, the effect of Pb2+ on the Ca2+/CaM regulated biological activities cannot be described by the primary mechanism of ionic displacement (e.g., ionic mimicry). The focus of this study was to investigate the mechanism of lead toxicity through binding differences between Ca2+ and Pb2+ for CaM, an essential intracellular trigger protein with two EF-Hand Ca2+-binding sites in each of its two domains that regulates many molecular targets via Ca2+-induced conformational change. Fluorescence changes in phenylalanine indicated that Pb2+ binds with 8-fold higher affinity than Ca2+ in the N-terminal domain. Additionally, NMR chemical shift changes and an unusual biphasic response observed in tyrosine fluorescence associated with C-terminal domain sites EF-III and EF-IV suggest a single higher affinity Pb2+-binding site with a 3-fold higher affinity than Ca2+, coupled with a second site exhibiting affinity nearly equivalent to that of the N-terminal domain sites. Our results further indicate that Pb2+ displaces Ca2+ only in the N-terminal domain, with minimal perturbation of the C-terminal domain, however significant structural/dynamic changes are observed in the trans-domain linker region which appear to be due to Pb2+-binding outside of the known calcium-binding sites. These data suggest that opportunistic Pb2+-binding in Ca2+/CaM has a profound impact on the conformation and dynamics of the essential molecular recognition sites of the central helix, and provides insight into the molecular toxicity of non-essential metal ions.
  Graphical abstract
  
  PubDate: 2013-04-20T16:22:30Z
Metal complex–DNA binding: Insights from molecular dynamics and DFT/MM calculations
- Abstract: Publication date: July 2013
  Source:Journal of Inorganic Biochemistry, Volume 124
  Author(s): Angelo Spinello , Alessio Terenzi , Giampaolo Barone
  Molecular dynamics (MD) simulations, followed by density functional theory/molecular mechanics (DFT/MM) calculations, provided a detailed structure of the binding site between the cationic metallointercalator (dipyrido [3,2-a:2′,3′-c]phenazine)(glycinato)copper(II), [Cu(gly)(dppz)]+, and the two dodeca-deoxynucleotide duplexes [dodeca(dG-dC)]2 and [dodeca(dA-dT)]2. Three simultaneous DNA binding types were detected in the fully optimized DFT/MM structures: 1) metal coordination through exocyclic oxygen atoms of nitrogen bases; 2) intercalation of the dppz chromophore between stacked Watson–Crick AT–AT and GC–GC bases; and 3) hydrogen bonding between the glycinato ligand and amine groups or heterocyclic nitrogen atoms of DNA bases. Standard enthalpy and Gibbs free energy values were used to evaluate, in vacuo and in solution, the formation energy of both [Cu(gly)(dppz)]/dodecanucleotide complexes. The latter were in excellent agreement with the recently reported value of the experimental DNA-binding constant, providing a physical interpretation of the enthalpy, entropy and solvent contributions in the binding mechanism.
  Graphical abstract
  
  PubDate: 2013-04-20T16:22:30Z
Role of liver fatty acid binding protein in hepatocellular injury: Effect of CrPic treatment
- Abstract: Publication date: July 2013
  Source:Journal of Inorganic Biochemistry, Volume 124
  Author(s): Weijiang Fan , Kun Chen , Guoqiang Zheng , Wenhang Wang , Anguo Teng , Anjun Liu , Dongfeng Ming , Peng Yan
  This study was designed to investigate the molecular mechanisms of chromium picolinate (CrPic, Fig. 1) hepatoprotective activity from alloxan-induced hepatic injury. Diabetes is induced by alloxan-treatment concurrently with the hepatic injury in mice. In this study, we investigate the protective effect of CrPic treatment in hepatic injury and the signal role of liver fatty acid binding protein in early hepatocellular injury diagnostics. In this study, alanine aminotransferase (ALT; EC 2.6.1.2) and aspartate aminotransferase (AST; EC 2.6.1.1) levels in the alloxan group were higher 71% and 50%, respectively, than those of the control group (ALT: 14.51±0.74; AST: 22.60±0.69). The AST and ALT levels in CrPic group were of minimal difference compared to the control groups. Here, CrPic exhibited amelioration alloxan induced oxidative stress in mouse livers. A significant increase in liver fatty acid-binding protein (L-FABP) was observed, which indicates increased fatty acid utilization in liver tissue [1]. In this study, the mRNA levels of L-FABP increased in both the control (1.1 fold) and CrPic (0.78 fold) groups compared the alloxan group. These findings suggest that hepatic injury may be prevented by CrPic, and is a potential target for use in the treatment of early hepatic injury.
  Graphical abstract
  
  PubDate: 2013-04-17T16:23:44Z
Size matters, so does shape: Inhibition of transcription of T7 RNA polymerase by iron(II) clathrochelates
- Abstract: Publication date: July 2013
  Source:Journal of Inorganic Biochemistry, Volume 124
  Author(s): Valentin V. Novikov , Oleg A. Varzatskii , Valentina V. Negrutska , Yurii N. Bubnov , Larisa G. Palchykovska , Igor Y. Dubey , Yan Z. Voloshin
  Coordination and organoelement compounds are rarely proposed as the drug candidates despite their vast potential in the area owing to their strictly controlled geometry and rather extensive surface. This is the first example of the inhibition of transcription in the system of T7 RNA polymerase by cage metal complexes. Their IC50 values reach as low as the nanomolar range, placing them among the most potent metal-based transcription inhibitors.
  Graphical abstract
  
  PubDate: 2013-04-17T16:23:44Z
In vitro effects of some gold complexes on Na+/K+ ATPase activity and cell proliferation
- Abstract: Publication date: July 2013
  Source:Journal of Inorganic Biochemistry, Volume 124
  Author(s): Voin Petrović , Mirjana Čolović , Danijela Krstić , Ana Vujačić , Sandra Petrović , Gordana Joksić , Živadin Bugarčić , Vesna Vasić
  The in vitro influence of gold(III) complexes, H[AuCl4], [Au(DMSO)2Cl2]Cl and [Au(bipy)Cl2]Cl (bipy = 2,2′-bipyridine), upon commercially available Na+/K+ ATPase activity, purified from porcine brain cortex, was investigated. Additionally, the complexes were tested on human lymphocytes, and incidence of micronuclei and cell proliferation index was determined. Concentration-dependent inhibition of the enzyme for all three compounds was obtained, but with differing potencies. Calculated IC50 from Hill analysis were (in M): 5.75×10−7, 5.50×10−6 and 3.98×10−5, for H[AuCl4], [Au(DMSO)2Cl2]Cl and [Au(bipy)Cl2]Cl, respectively, while Hill coefficient values, n, were above 1 in all cases. This inhibition can be prevented using –SH donating ligands such as L-Cys and glutathione, and these ligands can also cause a recovery of the enzyme activity after the induced inhibition. Kinetic analysis demonstrated that each of the studied gold(III) complexes affects Na+/K+ ATPase reducing maximum enzymatic velocity, Vmax, but not significantly changing the affinity for the substrate (KM value), implying a noncompetitive mode of the interaction. Furthermore, among investigated gold(III) complexes, the [Au(bipy)Cl2]Cl complex exhibits a strong cytotoxic effect on human lymphocytes, which suggests its potential for use in antitumor therapy.
  Graphical abstract
  
  PubDate: 2013-04-14T16:04:11Z
High affinity of copper(II) towards amoxicillin, apramycin and ristomycin. Effect of these complexes on the catalytic activity of HDV ribozyme
- Abstract: Publication date: July 2013
  Source:Journal of Inorganic Biochemistry, Volume 124
  
  Three representatives of the distinct antibiotics groups: amoxicillin, apramycin and ristomycin A were studied regarding their impact on hepatitis D virus (HDV) ribozyme both in the metal-free form and complexed with copper(II) ions. Hence the Cu(II)-ristomycin A complex has been characterized by means of NMR, EPR, CD and UV–visible spectroscopic techniques and its binding pattern has been compared with the coordination modes estimated previously for Cu(II)-amoxicillin and Cu(II)-apramycin complexes. It has thus been found that all three antibiotics bind the Cu(II) ion in a very similar manner, engaging two nitrogen and two oxygen donors into coordination with the square planar symmetry in physiological conditions. All three tested antibiotics were able to inhibit the HDV ribozyme catalysis. However, in the presence of the complexes, the catalytic reactions were almost completely inhibited. It was important therefore to check whether the complexes used in lower concentrations could inhibit the HDV ribozyme catalytic activity, thus creating opportunities for their practical application. It turned out that the complexes used in the concentrations of 50μM influenced the catalysis much less effectively comparing to the 200 micromolar concentration. The kobs values were lower than those observed in the control reaction, in the absence of potential inhibitors: 2-fold for amoxicillin, ristomycin A and 3.3-fold for apramycin, respectively.
  Graphical abstract
  
  PubDate: 2013-04-10T23:54:34Z
Novel method for rapid copper chelation assessment confirmed low affinity of D-penicillamine for copper in comparison with trientine and 8-hydroxyquinolines
- Abstract: Publication date: June 2013
  Source:Journal of Inorganic Biochemistry, Volume 123
  
  Copper is an essential trace element involved in many physiological processes. Since disorder of copper homeostasis is observed in various pathologies, copper chelators may represent a promising therapeutic tool. This study was aimed at: 1) formation of an in vitro methodology for screening of copper chelators, and 2) detailed analysis of the interaction of copper with clinically used D-penicillamine (D-PEN), triethylenetetramine (trientine), experimentally tested 8-hydroxyquinolines, and the disodium salt of EDTA as a standard chelator. Methodology based on bathocuproinedisulfonic acid disodium salt (BCS), usable at (patho)physiologically relevant pHs (4.5–7.5), enabled assessment of both cuprous and cupric ions chelation and comparison of the relative affinities of the tested compounds for copper. In the case of potent chelators, the stoichiometry could be estimated too. Clioquinol, chloroxine and EDTA formed very stable complexes with Cu+/Cu2+ at all tested pHs, while copper complexes with trientine were stable only under neutral or slightly acidic conditions. Non-substituted 8-hydroxyquinoline was a less efficient copper chelator, but still unequivocally more potent than D-PEN. Both 8-hydroxyquinoline and D-PEN chelation potencies, similarly to that of trientine, were pH-dependent and decreased with pH. Moreover, only D-PEN was able to reduce cupric ions. Conclusively, BCS assay represents a rapid, simple and precise method for copper chelation measurement. In addition, lower binding affinity of D-PEN compared with 8-hydroxyquinolines and trientine was demonstrated.
  Graphical abstract
  
  PubDate: 2013-04-10T23:54:34Z
The preparation of N-acetyl-Co(III)-microperoxidase-8 (NAcCoMP8) and its ligand substitution reactions: A comparison with aquacobalamin (vitamin B12a)
- Abstract: Publication date: June 2013
  Source:Journal of Inorganic Biochemistry, Volume 123
  
  The synthesis of the Co(III) porphyrin octapeptide N-acetyl-Co(III) microperoxidase-8 (NAcCoMP8) is described. NAcCoMP8 provides a means of comparing and contrasting the chemistry of Co(III) porphyrins and corrins to assess the influence of the macrocycle. Log K values, and ΔH and ΔS, for the coordination of anionic (CN−, N3 −, NO2 −, HSO3 −) and neutral (pyridine, N-methylimidazole, methoxylamine and hydroxylamine) ligands by aquacobalamin (H2OCbl+) and NAcCoMP8 are reported. Anions bind more strongly to H2OCbl+ than to NAcCoMP8 while the converse is true for the neutral ligands. Density Functional Theory (DFT) calculations and QTAIM analyses suggest the bonding between Co(III) and these ligands is predominantly ionic although anionic ligands induce a significant covalency, the extent of which is important for the stability of the complex. The CoL bond length (L=an anion) in a Co(III) corrin, while longer than in a Co(III) porphyrin, is shorter than might be expected as assessed from CoL bond lengths when L=neutral ligand. It is likely that this stems from coulombic interaction between L and the residual charge at the metal center (2+ in corrin; 1+ in porphyrin). Co(III) in H2OCbl+ is more labile towards substitution by CN− than NAcCoMP8 but the converse is true when the entering ligand is neutral N-methylimidazole. The extent of participation of the incoming ligand in the transition state of the reaction is controlled by the log K value so the nature of the incoming ligand determines in which of these two macrocyclic systems Co(III) is the more labile.
  Graphical abstract
  
  PubDate: 2013-04-10T23:54:34Z
Direct interactions between Z-DNA and alkaline earth cations, discovered in the presence of high concentrations of MgCl2 and CaCl2
- Abstract: Publication date: July 2013
  Source:Journal of Inorganic Biochemistry, Volume 124
  
  In this study, crystals of Z-DNA hexamer d(CGCGCG) complexed with MgCl2 and CaCl2 were obtained in the presence of high concentrations of alkaline earth salts (500mM) using a temperature control technique, and their crystal structures were determined at 1.3Å resolution. Mg2+ and Ca2+ cations in these structures tend to interact directly with phosphate groups of Z-DNA duplexes; however, they tend to form water-mediated interactions with Z-DNA in the presence of lower concentrations of alkaline earth salts. In these crystals, a DNA duplex was laid along its c-axis and interacted with its 6 neighboring DNA duplexes through coordination bonds of PO…(Mg2+ or Ca2+)…OP. A symmetrical hexagonal Z-DNA duplex assembly model may explain DNA condensation caused by alkaline earth salts. These structures offer insights into the functions of alkaline earth cations essential to the structures and assembly of Z-DNA duplexes.
  Graphical abstract
  
  PubDate: 2013-04-10T23:54:34Z
Evaluation of the binding of polyhedral borane anions to representative proteins
- Abstract: Publication date: July 2013
  Source:Journal of Inorganic Biochemistry, Volume 124
  
  The ability of three polyhedral borane anions, [B20H18]2−, [B20H17SH]4−, and [B20H19]3−, to bind to proteins was evaluated by measuring the total boron content using inductively coupled plasma-atomic emission spectroscopy after purification by gel electrophoresis. Results were correlated to the known chemical reactivity of the compounds as well as the reported murine biodistributions of the liposomally encapsulated sodium salts of each of the polyhedral borane anions. Qualitative reactions were performed with the [B20H18]2− anion to determine the potential reactivity with simple molecular building blocks.
  Graphical abstract
  
  PubDate: 2013-04-10T23:54:34Z
The Abilities of Selenium Dioxide and Selenite Ion to Coordinate DNA-Bound Metal Ions and Decrease Oxidative DNA Damage
- Abstract: Available online 6 April 2013
  Publication year: 2013
  Source:Journal of Inorganic Biochemistry
  
  Several transition metals react with H2O2 and produce reactive oxygen species (ROS) responsible for oxidative damage linked to many diseases and disorders, and species that form coordination complexes with these metal ions show promise as antioxidants. The present study demonstrates that metal-mediated radical and non-radical oxidative DNA damage decreases when selenium dioxide (SeO2) and sodium selenite (Na2SeO3) are present. Radical-induced damage is associated with production of 8-hydroxy-2’-deoxyguanosine (8-OH-dG), which arises from ROS generated at or near the guanine base, and the selenium compounds reduce Fe(II)-, Cr(III)- and Cu(II)-mediated radical damage to differing degrees based on the identity of the metal ion and the order in which the metals, selenium compounds and DNA are combined. Radical damage arising from Fe(II) and Cr(III) decreases substantially when they are pre-incubated with the selenium compounds prior to adding DNA. Non-radical damage is associated with oxidation of the adenine base in the presence of high H2O2 concentrations through an ionic mechanism, and this type of damage also decreases significantly when the selenium compounds are allowed to interact with the metal ions before adding DNA. Fluorescence studies using dihydrodichlorofluorescein diacetate (DCF-DA) to probe ROS formation indicate that the majority of the SeO2- and SeO3 2ˉ-metal systems in combination with H2O2 (no DNA present) produce ROS to the same degree as the metal/H2O2 systems in the absence of the selenium compounds, suggesting that selenium-metal complexes react with H2O2 in a sacrificial manner that protects DNA from oxidative damage.
  Graphical abstract
  
  PubDate: 2013-04-07T21:21:28Z
Synthesis, structure and in vitro cytotoxic studies of novel paramagnetic palladium(III) complexes with hematoporphyrin IX
- Abstract: Available online 2 April 2013
  Publication year: 2013
  Source:Journal of Inorganic Biochemistry
  
  Two coordination compounds of PdIII with hematoporphyrin IX ((7,12-bis(1-hydroxyethyl)-3,8,13,17-tetramethyl-21H-23H-porphyn-2,18-dipropionic acid), Hp), dinuclear [PdIII 2(Hp-3H)Cl3(H2O)5].2PdCl2, 1 and mononuclear [PdIII(Hp-2H)Cl(H2O)].H2O, 2 were obtained and structurally characterized in solid state and solution using spectroscopic, thermal and magnetic methods. In the dinuclear complex, 1 one of the PdIII ions is coordinated to the deprotanated COO- groups from the side chains of the porphyrin ligand and the second PdIII ion - to two adjacent pyrrole N-atoms on the top of the porphyrin ring and a PdIII-Hp-PdIII system was formed. The PdIII ion in the mononuclear complex, 2 is incorporated in the porphyrin core. The PdIII centers in both complexes have a distorted octahedral coordination filled with additional donor species such as Cl- and H2O. The studied compounds showed in vitro cell growth inhibitory effects at micromolar concentration against a panel of human tumor cell lines. A DNA fragmentation assay indicated that the growth inhibitory effects are at least partly mediated by induction of apoptosis.
  Graphical abstract
  
  PubDate: 2013-04-04T16:26:49Z
Copper(II) interacting with the non-steroidal antiinflammatory drug flufenamic acid: Structure, antioxidant activity and binding to DNA and albumins
- Abstract: June 2013
  Publication year: 2013
  Source:Journal of Inorganic Biochemistry, Volume 123
  
  Copper(II) complexes with the non-steroidal antiinflammatory drug flufenamic acid (Hfluf) in the presence of N,N-dimethylformamide (DMF) or nitrogen donor heterocyclic ligands (2,2′-bipyridylamine (bipyam), 1,10-phenanthroline (phen), 2,2′-bipyridine (bipy) or pyridine (py)) have been synthesized and characterized. The crystal structures of [Cu2(fluf)4(DMF)2], 1, and [Cu(fluf)(bipyam)Cl], 2, have been determined by X-ray crystallography. Density functional theory (DFT) (CAM-B3LYP/LANL2DZ/6-31G**) was employed to determine the structure of complex 2 and its analogues (complexes [Cu(fluf)(phen)Cl], 3, [Cu(fluf)(bipy)Cl], 4 and [Cu(fluf)2(py)2], 5). Time-dependent DFT calculations of doublet–doublet transitions show that the lowest-energy band in the absorption spectrum of 2–5 has a mixed d–d/LMCT character. UV study of the interaction of the complexes with calf-thymus DNA (CT DNA) has shown that the complexes can bind to CT DNA with [Cu(fluf)(bipy)Cl] exhibiting the highest binding constant to CT DNA. The complexes can bind to CT DNA via intercalation as concluded by studying the cyclic voltammograms of the complexes in the presence of CT DNA solution and by DNA solution viscosity measurements. Competitive studies with ethidium bromide (EB) have shown that the complexes can displace the DNA-bound EB suggesting strong competition with EB. Flufenamic acid and its Cu(II) complexes exhibit good binding affinity to human or bovine serum albumin protein with high binding constant values. All compounds have been tested for their antioxidant and free radical scavenging activity as well as for their in vitro inhibitory activity against soybean lipoxygenase showing significant activity with [Cu(fluf)(phen)Cl] being the most active.
  Graphical abstract
  
  PubDate: 2013-03-23T09:46:04Z
Bio-inspired amino acid oxidation by a non-heme iron catalyst
- Abstract: June 2013
  Publication year: 2013
  Source:Journal of Inorganic Biochemistry, Volume 123
  
  This study reports the kinetics and mechanism of Fe(III)-catalyzed oxidative decarboxylation and deamination of a series of acyclic (α-aminoisobutyric acid, α-(methylamino)isobutyric acid, alanine, norvaline, and 2-aminobutyric acid) and cyclic (1-aminocyclopropane-1-carboxylic acid, 1-amino-1-cyclobutanecarboxylic acid, 1-aminocyclopentanecarboxylic acid, and 1-aminocyclohexanecarboxylicacid) amino acids using hydrogen peroxide, t-butyl hydroperoxide, iodosylbenzene, m-chloroperbenzoic acid, and peroxomonosulphate as oxidant in 75% DMF–25% water solvent mixture. Model complex [FeIVO(SALEN)]•+ (SALENH2: N,N′-bis(salicylidene)ethylenediamine) was generated by the reaction of FeIII(SALEN)Cl and H2O2 in CH3CN at 278K as reported earlier. This method provided us high-valent oxoiron species, stable enough to ensure the direct observation of the reaction with amino acids.
  Graphical abstract Highlights [FeIII(SALEN)Cl] (SALENH2: N,N′-bis(salicylidene)ethylenediamine) is an active and selective catalyst in the oxidation of a series of cyclic and acyclic amino acids to ethylene and carbonyls and thus serves as functional models for ACC oxidase. ► Kinetics of Fe(III)-catalyzed oxidation of amino acids with various oxidants. ► Stoichiometric oxidation of ACC with high valent iron-oxo intermediate. ► Suggested mechanism for the ACC oxidase.
  
  PubDate: 2013-03-23T09:46:04Z
Mono- and dicationic Re(I)/99mTc(I) tricarbonyl complexes for the targeting of energized mitochondria
- Abstract: June 2013
  Publication year: 2013
  Source:Journal of Inorganic Biochemistry, Volume 123
  
  The enhanced negative mitochondrial membrane potential of tumor cells can increase the cell accumulation of triphenylphosphonium (TPP) derivatives, which prompted us to investigate TPP-containing Re(I)/99mTc organometallic compounds as probes for in vivo targeting of energized mitochondria. Novel compounds (Re1–Re4/Tc1–Tc4) were obtained with bifunctional chelators of the pyrazole-diamine (N,N,N-donors) and pyrazole-aminocarboxylic (N,N,O-donors) type, functionalized with TPP pharmacophores that have been introduced at the central amine of the chelators using different spacers. In this way, dicationic (Re1–Re2, Tc1–Tc2) and monocationic (Re3–Re4, Tc3–Tc4) complexes with variable lipophilicity were synthesized. The 99mTc complexes (Tc1–Tc4) are highly stable under physiological conditions and their chemical identification was done by HPLC comparison with the Re congeners (Re1–Re4), which were fully characterized by common analytical techniques (electrospray ionization mass spectrometry (ESI-MS), IR, multinuclear NMR). The in vitro biological evaluation of Tc1–Tc4 was performed in a panel of human tumor cell lines (PC-3, MCF-7 and H69), including cell lines overexpressing P-glycoprotein (MCF-7/MDR1 and H69/Lx4), and in isolated mitochondria. All the tested complexes showed a low to moderate cellular and mitochondrial uptake and did not undergo significant P-glycoprotein (Pgp)-mediated efflux processes. In particular, the dication Tc2 and the monocation Tc4 presented the highest cellular and mitochondrial uptake. Their cellular uptake was shown to depend on the mitochondrial (Δψm) and plasma membrane (Δψp) potentials. Altogether, the biological properties of these compounds suggest that they might be relevant for the design of radioactive metalloprobes for in vivo targeting of mitochondria.
  Graphical abstract Highlights The first examples of triphenylphosphonium-containing Re(I)/99mTc(I) tricarbonyl complexes are reported, and evaluated in vitro as probes for the targeting of energized mitochondria of tumor cells. ► First examples of triphenyl phosphonium (TPP)-containing Re(I)/99mTc(I) complexes ► The newly synthesized complexes were obtained using pyrazolyl-based chelators ► The 99mTc complexes accumulate in several tumor cell lines of human origin ► Radioactive probes with high in vitro affinity towards tumor mitochondria ► New platforms to design metalloprobes for in vivo targeting of tumoral mitochondria
  
  PubDate: 2013-03-23T09:46:04Z
Dissecting the Kinetics of the NADP+ - FADH2 Charge Transfer Complex and Flavin Semiquinones in Neuronal Nitric Oxide Synthase
- Abstract: Available online 22 March 2013
  Publication year: 2013
  Source:Journal of Inorganic Biochemistry
  
  Electron flow within the neuronal nitric oxide synthase reductase domain (nNOSrd) includes hydride transfer from NADPH to FAD followed by two one-electron transfer reactions from FAD to FMN. We have used stopped flow spectrometry to closely monitor these electron transfer steps for both the wild type and the ΔG810 mutant of nNOSrd using a protocol involving both global analyses of the photodiode array spectral scans and curve fittings of single wavelength kinetic traces. The charge transfer complex and interflavin electron transfer events recorded at 750nm and 600nm, respectively, show the kinetics in different time frames. All electron transfer events are slow enough at 4°C to enable measurements of rate constants even for the fast charge transfer event. To our knowledge this is the first time the rate constants for the charge transfer between NADP+ and FADH2 have been determined for NOS. These procedures allow us to conclude that (1) binding of the second NADPH is necessary to drive the full reduction of FMN and; (2) charge transfer and the subsequent interflavin electron transfer have distinct spectral features that can be monitored separately with stopped flow spectroscopy. These studies also enable us to conclude that interflavin electron transfer reported at 600nm is not limiting in NOS catalysis.
  Graphical abstract
  
  PubDate: 2013-03-23T09:46:04Z
Editorial Board
- Abstract: May 2013
  Publication year: 2013
  Source:Journal of Inorganic Biochemistry, Volume 122
  
  PubDate: 2013-03-17T07:01:49Z
Contents
- Abstract: May 2013
  Publication year: 2013
  Source:Journal of Inorganic Biochemistry, Volume 122
  
  PubDate: 2013-03-17T07:01:49Z
Organic cadmium complexes as proteasome inhibitors and apoptosis inducers in human breast cancer cells
- Abstract: June 2013
  Publication year: 2013
  Source:Journal of Inorganic Biochemistry, Volume 123
  
  Although cadmium (Cd) is a widespread environmental contaminant and human carcinogen, our studies indicate an organic Cd complex to be a potent inhibitor of proteasomal chymotrypsin-like (CT-like) activity, further capable of inducing apoptosis in a cancer cell-specific manner. It has been reported that the ligands indole-3-butyric acid (L1) and indole-3-propionic acid (L2) have cancer-fighting effects when tested in a rat carcinoma model. In addition, 3, 5-diaminobenzoic acid o-vanillin Schiff bases (L3) have high antimicrobial activity and a large number of Schiff base complexes have been reported to have proteasome-inhibitory activity. We therefore hypothesized that synthetic forms of Cd in combination with L1, L2 and L3 may have proteasome-inhibitory and apoptosis-inducing activities, which would be cancer cell-specific. To test this hypothesis, we have synthesized three novel Cd-containing complexes: [Cd2(C12H12O2N)4(H2O)2]·2H2O (Cd1), [Cd2(C11H10O2N)4(H2O)2]·2H2O (Cd2) and [Cd(C7H4N2O2)(C8H6O2)2]·2H2O (Cd3), by using these three ligands. We sought out to characterize and assess the proteasome-inhibitory and anti-proliferative properties of these three Cd complexes in human breast cancer cells. Cd1, Cd2 and Cd3 were found to effectively inhibit the chymotrypsin-like activity of purified 20S proteasome with IC50 values of 2.6, 3.0 and 3.3μΜ, respectively. Moreover, inhibition of cancer cell proliferation also correlated with this effect. As a result of proteasomal shutdown, the accumulation of ubiquitinated proteins and the proteasome target IκB-α protein as well as induction of apoptosis were observed. To account for the cancer specificity of this effect, immortalized, non-tumorigenic breast MCF10A cells were used under the same experimental conditions. Our results indicate that MCF10A cells are much less sensitive to the Cd1, Cd2 and Cd3 complexes when compared to MDA MB 231 breast cancer cells. Therefore, our study suggests that these Cd organic complexes are capable of inhibiting tumor cellular proteasome activity and consequently induce cancer cell-specific apoptotic death.
  Graphical abstract Highlights Three cadmium complexes Cd1, Cd2 and Cd3 were synthesized, nucleophilic susceptibilities analyzed and proteasome-inhibitory effects in tumor cells were evaluated. ► Three cadmium complexes were synthesized and characterized ► Inhibitory activities on breast cancer cells ► ER-independent mechanism of action ► Exhibit more biological activity in breast cancer cells than in nontumorigenic cells
  
  PubDate: 2013-03-17T07:01:49Z
Editorial Board
- Abstract: April 2013
  Publication year: 2013
  Source:Journal of Inorganic Biochemistry, Volume 121
  
  PubDate: 2013-03-14T17:24:46Z
Novel water-soluble 99mTc(I)/Re(I)-porphyrin conjugates as potential multimodal agents for molecular imaging
- Abstract: May 2013
  Publication year: 2013
  Source:Journal of Inorganic Biochemistry, Volume 122
  
  The synthesis and characterization of two novel water soluble porphyrins with three meso pyridyl rings and one peripheral chelator — either a diethylenetriamine unit (4) or a bipyridyl fragment (8) — for binding to the {99mTc(CO)3}+ moiety is reported. In 8, despite the presence of a flexible and hydrophilic PEG-like linker that connects the bpy unit to the macrocycle, good water solubility was only obtained by methylation of the pyridyl N atoms that provided three extra positive charges. Furthermore, the water-soluble conjugates of 4 and 8 with either one fac-{Re(CO)3}+ (9 and 10, respectively) or one fac-{99mTc(CO)3}+ fragment (9a and 10a, respectively) are described.
  Graphical abstract Highlights The synthesis and characterization of two novel water soluble porphyrins bearing one peripheral chelator — either a diethylenetriamine unit (4) or a bipyridyl fragment (8) — in meso position and of their conjugates with either one fac-{Re(CO)3}+ (9 and 10, respectively) or one fac-{99mTc(CO)3}+ fragment (9a and 10a, respectively) are described. ► Two porphyrins for binding the {99mTc(CO)3}+ moiety were prepared and characterized. ► Site-specific and highly stable labeling with the {99mTc(CO)3}+ moiety was achieved. ► Full characterization was performed on the corresponding cold {Re(CO)3}+ conjugates. ► The 99mTc-porphyrin conjugates combine radio and optical imaging modalities. ► We describe here the first, thoroughly characterized, 99mTc-porphyrin conjugates.
  
  PubDate: 2013-03-05T21:19:46Z
Platinum-based drugs and proteins: Reactivity and relevance to DNA adduct formation
- Abstract: May 2013
  Publication year: 2013
  Source:Journal of Inorganic Biochemistry, Volume 122
  
  The mechanism of action of clinically used Pt-based drugs is through the formation of stable DNA adducts occurring at the nitrogen in position 7 of guanine (N7) and involving one or two spatially closed residues. Nevertheless, proteins can represent alternative targets since in particular sulfur groups, present in cysteine or methionine residues, can efficiently coordinate platinum. Here we have characterized the reactivity profile of cisplatin, transplatin and of two trans-platinum amine derivatives (TPAs) towards three different proteins, bovine α-lactalbumin (α-LA), hen egg lysozyme (LYS) and human serum albumin (HSA). Our results demonstrate that generally the tested metal complexes react with the selected target causing protein oligomerization, likely through a cross-linking reaction. Interestingly, the extent of such a process is largely modulated by the target protein and by the chemical features of the metal complex, TPAs being the most efficient platinating agents. From a structural point of view the resulting reaction products turned out to be depending on the nature of the metal complexes. However, in all instances, a transfer reaction of the metal complex to DNA can also occur, maintaining the relevance of nucleic acids as a biological target. These results can be used to better rationalize the different pharmacological profiles reported for cisplatin and TPAs and can help in designing more predictive SARs within the series.
  Graphical abstract Highlights Herein tested Pt-based compounds react with the selected proteins causing oligomerization, likely through a cross-linking reaction. The extent of such a process is largely modulated by the target protein and by the chemical features of the metal complex, TPAs being the most efficient platinating agents. ► Proteins as target, carrier or reservoir systems for platinum-based drugs ► Oligomerization of proteins is promoted by Pt-adduct formation. ► Pt-protein adducts are different according to the ligands and the protein involved. ► Pt(II) can be transferred from proteins to DNA.
  
  PubDate: 2013-03-02T11:56:45Z
Impact of metal on the DNA photo-induced cleavage activity of a family of Phterpy complexes
- Abstract: May 2013
  Publication year: 2013
  Source:Journal of Inorganic Biochemistry, Volume 122
  
  A family of Phterpy complexes, [Mn(Phterpy)2][N(CN)2]2·0.5H2O (1), [Fe(Phterpy)2](NO3)2 (2), [Ni(Phterpy)2](NO3)2 (3), [Ni(Phterpy)2]Cl2·10H2O (4), [Cd(Phterpy)2](NO3)2·2H2O (5) and [Zn(Phterpy)Cl2] (6) (Phterpy=4′-phenyl-2,2′:6′,2″-terpyridine), have been synthesized and structurally characterized, and their DNA binding and photo-induced DNA cleavage activities have been investigated. These complexes display binding propensity to the CT-DNA giving a relative order: 1 > 4 > 3, 5, 2, 6. Under dark or ambient lighting conditions, all complexes show no efficient DNA cleavage activity to pBR322 DNA. While on irradiation with UV-A light of 365nm, complexes of 1, 3 and 4 exhibit significant cleavage activities. In the presence of H2O2 as a revulsant or an activator, the cleavage ability of complex 2 is obviously enhanced. Complexes 5 and 6 do not exhibit any apparent chemical nuclease activities under irradiation conditions or with the addition of H2O2. The DNA photo-induced cleavage activities are consistent with the number of single-electron in the central metal ion of complexes and singlet oxygen and hydroxyl radical are found as the reactive oxygen species.
  Graphical abstract Highlights In attempt to obtain more insight on the selectivity and efficiency of DNA cleavage with different transition metal complexes, herein, we have prepared a series of mononuclear d-metal complexes and investigated their DNA cleavage activities. ► A family of Phterpy complexes have been synthesized and structurally characterized. ► Their DNA binding and photo-induced DNA cleavage activities have been studied. ► Singlet oxygen and hydroxyl radical are found as the reactive oxygen species.
  
  PubDate: 2013-03-02T11:56:45Z
Luminescent material based on the [Eu(TTA)3(H2O)2] complex incorporated into modified silica particles for biological applications
- Abstract: Available online 26 February 2013
  Publication year: 2013
  Source:Journal of Inorganic Biochemistry
  
  Amino-functionalized luminescent silica particles were investigated for use in immunoassays. The particles were prepared by the Stöber method where the [Eu(TTA)3(H2O)2] complex (TTA: 3-thenoyltrifluoroacetonate) was incorporated into silica particles during the hydrolysis and condensation of TEOS: tetraethylorthosilicate, Then, the amino groups were introduced in the particle surface using APTS: 3-aminopropyltriethoxisilane. The resulting particles were characterized by scanning electron microscopy (SEM), X ray diffraction (XRD) and photoluminescence spectroscopy. In order to demonstrate the viability of the use of luminescent particles as optical markers, an enzyme-substrate reaction was performed using HRP: horseradish peroxidase. It was possible to verify the binding of HRP–oxidized LDL (low density lipoprotein) and anti-oxLDL antibody–luminescent silica particles through the evaluation of the presence of HRP. The bioassay data open a broad field for the development of protein-tagged luminescent particles for use in biomedical sciences.
  Graphical abstract Highlights Luminescent marker prepared by the Stöber method, incorporating the [Eu(TTA)3(H2O)2] complex, as a potential candidate for development of the protocol for the quantification of the oxLDL. ► Amino-functionalized luminescent silica particles were prepared and characterized. ► Viability of the use of luminescent rare earth particles as optical markers was examined. ► Enzyme-substrate reaction was performed using HRP. ► The bioassay data open a broad field for the biomedical sciences.
  
  PubDate: 2013-02-27T14:26:24Z
Selective damage to hyphal form through light-induced delivery of nitric oxide to Candida albicans colonies
- Abstract: Available online 22 February 2013
  Publication year: 2013
  Source:Journal of Inorganic Biochemistry
  
  Candida albicans, an opportunistic fungal pathogen, causes severe to life-threatening infections in immunocompromised hosts (e.g. HIV patients, burn victims). Conversion of the commensal yeast form to the invasive hyphal form, triggered by environmental cues, initiates such episodes. Although the antifungal activity of nitric oxide (NO) has been established, very few convenient NO-donating systems for treating C. albicans infection have been reported. In this work, a biocompatible NO-donating material that delivers NO upon illumination with visible light has been employed to eradicate C. albicans in a dose-dependent way. Careful studies on the yeast and hyphal form with this NO donor have revealed that the hyphal form is more susceptible to NO exposure than the yeast variety. Results of this work suggest that materials of this type could find use in thwarting invasion of the hyphal form of the fungus in cases of invasive C. albicans infection.
  Graphical abstract Highlights Light-triggered NO delivery from a manganese nitrosyl entrapped within a porous material eradicates Candida albicans colonies in a dose-dependent manner. The invasive hyphal form of the fungus exhibits more susceptibility toward NO than the commensal yeast form. ► A photoactive nitric oxide-donating material has been employed to eradicate Candida albicans grown in a skin and soft tissue infection (SSTI) model ► The effects of nitric oxide on individually-grown yeast and hyphal form of the fungus have been determined ► The hyphal form exhibits more sensitivity to nitric oxide than the yeast form ► Nitric oxide could be a potential therapeutic to prevent invasive Candida infection
  
  PubDate: 2013-02-24T09:22:13Z
Improvement of the antihypertensive capacity of candesartan and trityl candesartan by their SOD mimetic copper(II) complexes
- Abstract: Available online 21 February 2013
  Publication year: 2013
  Source:Journal of Inorganic Biochemistry
  
  Two new complexes [Cu(Cand)(H2O)4] [1] and [Cu2(TCand)4(H2O)2].4H2O [2] (Cand=candesartan; TCand=trityl candesartan) have been synthesized and thoroughly characterized. The FTIR, Raman, EPR and diffuse reflectance spectra of the solid compounds show a dimeric complex for [2] with carboxylate bridging of the type found in copper(II) acetate. Both elemental analysis and thermal measurements allow the determination of the total stoichiometries of both complexes. The stability measurements show that the compounds are stable in ethanolic solutions at least for 1 h, while the preservation of the overall stochiometry for both species in solution has been determined by spectrophotometric titrations. By metal complexation the absence of antioxidant behavior of both sartans has been improved. Complexes [1] and [2] are strong superoxidedismutase mimetic compounds and complex [2] also behaves as a peroxyl radical scavenger. Furthermore, this higher antioxidant activity works in parallel with the improvement of the expansive activity over the angiotensin II-induced contracted human mesangial cells. These new complexes exhibit even higher efficiency as drugs in comparison with the free non-complexed medication with increased antioxidant ability expressing higher capacity to block the angiotensin II contractile effect. This study provides a new insight into the development of copper(II) complexes as potential drugs.
  Graphical abstract Highlights Candesartan (fig) and Trityl Candesartan block the angiotensin II contractile effect in human mesangial cells. Their copper complexes behave as good ROS (reactive oxygen species) scavengers and improve their expansive activities. ► Modification of antihypertensive drugs by Cu(II) complexation. ► The new compounds were characterized by physicochemical measurements. ► In contrast to the ligands, the complexes displayed antioxidant properties. ► Sartans are able to block the angiotensin II contractile effect in cells. ► The complexes behaved as potential drugs improving the expansive activity of sartans.
  
  PubDate: 2013-02-24T09:22:13Z
Peroxidase activity stabilization of cytochrome P450BM3 by rational analysis of intramolecular electron transfer
- Abstract: May 2013
  Publication year: 2013
  Source:Journal of Inorganic Biochemistry, Volume 122
  
  Combined quantum mechanical and molecular mechanical (QM/MM) calculations were used to explore the electron pathway involved in the suicide inactivation of cytochrome P450BM3 from Bacillus megaterium. The suicide inactivation is a common phenomenon observed for heme peroxidases, in which the enzyme is inactivated as a result of self-oxidation mediated by highly oxidizing enzyme intermediates formed during the catalytic cycle. The selected model was a mutant comprising only the heme domain (CYPBM3 21B3) that had been previously evolved to efficiently catalyze hydroxylation reactions with hydrogen peroxide (H2O2) as electron acceptor. An extensive mapping of residues involved in electron transfer routes was obtained from density functional calculations on activated heme (i.e. Compound I) and selected amino acid residues. Identification of oxidizable residues (electron donors) was performed by selectively activating/deactivating different quantum regions. This method allowed a rational identification of key oxidizable targets in order to replace them for less oxidizable residues by site-directed mutagenesis. The residues W96 and F405 were consistently predicted by the QM/MM electron pathway to hold high spin density; single and double mutants of P450BM3 on these positions (W96A, F405L, W96A/F405L) resulted in a more stable variants in the presence of hydrogen peroxide, displaying a similar reaction rate than P450BM3 21B3. Furthermore, mass spectrometry confirmed these oxidation sites and corroborated the possible routes described by QM/MM electron transfer (ET) pathways.
  Graphical abstract Highlights QM/MM rational approach to obtain cytochrome P450 stable variants for peroxidase activity. ► Combined quantum mechanical and molecular mechanical analysis of CYPBM3 ► Extensive mapping of residues involved in electron transfer routes on Compound I ► Identification of oxidizable residues by activating/deactivating quantum regions ► Mutation of key oxidizable residues by site-directed mutagenesis ► A double variant 260 times more stable to peroxide inactivation was produced.
  
  PubDate: 2013-02-18T07:54:56Z
Metal vs. chalcogen competition in the catalytic mechanism of cysteine dioxygenase
- Abstract: May 2013
  Publication year: 2013
  Source:Journal of Inorganic Biochemistry, Volume 122
  
  Why the cysteine dioxygenase (CDO) cannot catalyze the oxidation of selenocysteine (Sec) but that of cysteine (Cys) is still an open question. In order to solve this question, the CDO model complex, the active site of CDO, and their selenium-substituted complexes have been selected as the computational models in this work. The stepwise donation of electron density during the first two reaction steps has been explored. In the first step, the electron density-donor ability of Se to donate to Fe is stronger than that of S; in the second step, S has the better electron density-donor ability to donate to O(2) than Se. Under the influence, in the Cys-bound complexes, the change of the oxidation state for the Fe center is II→III→II, while the Fe center in the Sec-bound complexes remains in the II oxidation state throughout. Considering that the ferric-superoxo species is an active oxidant and exhibits high reactivity in such reaction, it is speculated that the valence change of the Fe center makes the Cys-bound complexes effectively catalyze the oxidation of Cys, while the Sec-bound complexes cannot catalyze the oxidation of Sec. The competition for donation of electron density determines the valence change and the reaction ability.
  Graphical abstract Highlights The competition of charge transfer determines the catalytic activity of cysteine dioxygenase and the valences of Fe center are different for selenocysteine and cysteine in reaction processes. This work explains why cysteine dioxygenase cannot catalyze the oxidation of selenocysteine but that of cysteine. ► This work tries to understand the catalytic activity of cysteine dioxygenase for Sec and Cys. ► The competition of charge transfer determines the catalytic activity of cysteine dioxygenase. ► The valences of Fe center are different for Sec and Cys in reaction processes.
  
  PubDate: 2013-02-15T16:39:01Z
Complexes of Ferriheme Nitrophorin 4 with Low-Molecular Weight Thiol(ate)s Occurring in Blood Plasma
- Abstract: Available online 4 February 2013
  Publication year: 2013
  Source:Journal of Inorganic Biochemistry
  
  Nitrophorins are proteins occurring in the saliva of the blood-sucking insect Rhodnius prolixus to carry NO as a vasodilator and blood-coagulation inhibitor into the victim's tissue. It was suggested that the rate of NO release can be enhanced by blood-plasma component l-cysteine [J.M.C.Ribeiro, Insect Biochem. Mol. Biol. 26 (1996) 899–905]. However, the mechanism of the reaction is not clear. In the attempt to exploit the reaction in detail, complexes of nitrophorin 4 (NP4) with the thiols 2-mercaptoethanol, l-cysteine, and l-homocysteine and with HS- were formed and characterized under anaerobic conditions using absorption spectroscopy, X-ray crystallography, and EPR spectroscopy. In contrast to met-myoglobin, which is reduced by l-cysteine, all four compounds form low-spin FeIII complexes with NP4. The weak equilibration constants (167-5200M-1) neither support significant complexation nor the simple displacement of NO in vivo. Both amino acid based thiols form additional H-bonds with side chains of the heme pocket entry. Glutathione and l-methionine did not form a complex, indicating the specificity of the complexes with l-cysteine and l-homocysteine. Continuous wave EPR spectroscopy reveals the simultaneous existence of three low-spin systems in each case that are attributed to various protonation and/or conformational stages in the heme pocket. Electron nuclear double resonance (ENDOR) spectroscopy demonstrates that the thiol sulfurs are, at least in part, protonated. Overall, the results not only demonstrate the good accessibility of the NP4 heme center by biologically relevant thiols, but also represent the first structural characterization of a ferriheme protein in complex with l-cysteine, l-homocysteine, and HS-.
  Graphical abstract Highlights The X-ray structures of the heme protein nitrophorin 4 in complex with the three thiolates cysteine, homocysteine, and mercaptoethanol and with sulfide were solved. In all cases, the heme remains in the ferric state and specific side-chain interactions with the rest of the ligand are formed. ► X-ray structures of nitrophorin 4 with three thiolates and sulfide were solved. ► Cysteine, homocysteine, mercaptoethanol, and sulfide coordinate to the heme iron. ► The heme remains in the ferric state. ► Specific side-chain interactions with the rest of the ligand are formed. ► Pulsed EPR indicates that the sulfur of the thiolates is partially protonated.
  
  PubDate: 2013-02-05T18:26:47Z
Biological Activity and Cellular Uptake of [Ru(η5-C5H5)(PPh3)(Me2bpy)][CF3SO3] Complex
- Abstract: Available online 29 January 2013
  Publication year: 2013
  Source:Journal of Inorganic Biochemistry
  
  Anticancer activity of the new [Ru(η5-C5H5)(PPh3)(Me2bpy)][CF3SO3] (Me2bpy = 4,4’-dimethyl-2,2´-bipyridine) complex was evaluated in vitro against several human cancer cell lines, namely A2780, A2780CisR, HT29, MCF7, MDAMB231 and PC3. Remarkably, the IC50 values, placed in the nanomolar and sub-micromolar range, largely exceeded the activity of cisplatin. Binding to human serum albumin, either HSA (human serum albumin) or HSAfaf (fatty acid-free human serum albumin) does not affect the complex activity. Fluorescence studies revealed that the present ruthenium complex strongly quench the intrinsic fluorescence of albumin. Cell death by the [Ru(η5-C5H5)(PPh3)(Me2bpy)][CF3SO3] complex was reduced in the presence of endocytosis modulators and at low temperature, suggesting an energy-dependent mechanism consistent with endocytosis. On the whole, the biological activity evaluated herein suggests that complex could be a promising anticancer agent
  Graphical abstract Highlights Cytotoxicity is reduced by several endocytosis inhibitors (MDC, PAO, Ami, and CLQ) at low temperature, showing that cellular uptake mechanism is consistent with endocytosis. ► New “RuCp” compound containing a bidentate heteroaromatic ligand with outstanding cytotoxic properties against several human cancer cell lines; ► Albumin can be a vehicle of transport of this compound in the blood serum ► Binding to albumin does not affect citotoxicity ► Endocitosys was found the major cellular uptake mechanism.
  
  PubDate: 2013-01-30T21:08:16Z