Subjects -> BIOLOGY (Total: 3447 journals)
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BIOLOGY (1643 journals)                  1 2 3 4 5 6 7 8 | Last

Showing 1 - 200 of 1720 Journals sorted alphabetically
AAPS Journal     Hybrid Journal   (Followers: 30)
Achievements in the Life Sciences     Open Access   (Followers: 8)
ACS Pharmacology & Translational Science     Hybrid Journal   (Followers: 2)
ACS Synthetic Biology     Hybrid Journal   (Followers: 31)
Acta Biologica Colombiana     Open Access   (Followers: 7)
Acta Biologica Hungarica     Full-text available via subscription   (Followers: 5)
Acta Biologica Sibirica     Open Access   (Followers: 2)
Acta Biologica Turcica     Open Access   (Followers: 1)
Acta Biologica Venezuelica     Open Access  
Acta Biomaterialia     Hybrid Journal   (Followers: 30)
Acta Biotheoretica     Hybrid Journal   (Followers: 3)
Acta Chiropterologica     Full-text available via subscription   (Followers: 6)
acta ethologica     Hybrid Journal   (Followers: 4)
Acta Fytotechnica et Zootechnica     Open Access   (Followers: 1)
Acta Limnologica Brasiliensia     Open Access   (Followers: 4)
Acta Médica Costarricense     Open Access   (Followers: 2)
Acta Musei Silesiae, Scientiae Naturales     Open Access   (Followers: 1)
Acta Neurobiologiae Experimentalis     Open Access  
Acta Parasitologica     Hybrid Journal   (Followers: 12)
Acta Scientiae Biological Research     Open Access   (Followers: 1)
Acta Scientiarum. Biological Sciences     Open Access   (Followers: 2)
Acta Scientifica Naturalis     Open Access   (Followers: 3)
Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis     Open Access   (Followers: 1)
Actualidades Biológicas     Open Access   (Followers: 1)
Advanced Biosystems     Hybrid Journal  
Advanced Health Care Technologies     Open Access   (Followers: 10)
Advanced Journal of Graduate Research     Open Access   (Followers: 1)
Advanced Nonlinear Studies     Hybrid Journal  
Advanced Quantum Technologies     Hybrid Journal  
Advanced Studies in Biology     Open Access   (Followers: 1)
Advances in Antiviral Drug Design     Full-text available via subscription   (Followers: 2)
Advances in Bioinformatics     Open Access   (Followers: 20)
Advances in Biological Regulation     Hybrid Journal   (Followers: 4)
Advances in Biology     Open Access   (Followers: 12)
Advances in Cell Biology/ Medical Journal of Cell Biology     Open Access   (Followers: 30)
Advances in Cellular and Molecular Biology of Membranes and Organelles     Full-text available via subscription   (Followers: 14)
Advances in Developmental Biology     Full-text available via subscription   (Followers: 14)
Advances in DNA Sequence-Specific Agents     Full-text available via subscription   (Followers: 7)
Advances in Ecological Research     Full-text available via subscription   (Followers: 44)
Advances in Environmental Sciences - International Journal of the Bioflux Society     Open Access   (Followers: 19)
Advances in Enzyme Research     Open Access   (Followers: 11)
Advances in Experimental Biology     Full-text available via subscription   (Followers: 9)
Advances in Genome Biology     Full-text available via subscription   (Followers: 11)
Advances in High Energy Physics     Open Access   (Followers: 22)
Advances in Human Biology     Open Access   (Followers: 5)
Advances in Life Science and Technology     Open Access   (Followers: 20)
Advances in Life Sciences     Open Access   (Followers: 7)
Advances in Marine Biology     Full-text available via subscription   (Followers: 21)
Advances in Molecular and Cell Biology     Full-text available via subscription   (Followers: 26)
Advances in Organ Biology     Full-text available via subscription   (Followers: 2)
Advances in Planar Lipid Bilayers and Liposomes     Full-text available via subscription   (Followers: 3)
Advances in Space Biology and Medicine     Full-text available via subscription   (Followers: 7)
Advances in Structural Biology     Full-text available via subscription   (Followers: 6)
Advances in Tropical Biodiversity and Environmental Sciences     Open Access   (Followers: 3)
Advances in Virus Research     Full-text available via subscription   (Followers: 6)
Adversity and Resilience Science : Journal of Research and Practice     Hybrid Journal   (Followers: 2)
African Journal of Range & Forage Science     Hybrid Journal   (Followers: 12)
AFRREV STECH : An International Journal of Science and Technology     Open Access   (Followers: 3)
Ageing Research Reviews     Hybrid Journal   (Followers: 12)
Aging Cell     Open Access   (Followers: 26)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Agrokreatif Jurnal Ilmiah Pengabdian kepada Masyarakat     Open Access  
AJP Cell Physiology     Hybrid Journal   (Followers: 18)
AJP Endocrinology and Metabolism     Hybrid Journal   (Followers: 25)
AJP Lung Cellular and Molecular Physiology     Hybrid Journal   (Followers: 3)
Al-Kauniyah : Jurnal Biologi     Open Access  
Alasbimn Journal     Open Access   (Followers: 2)
Alces : A Journal Devoted to the Biology and Management of Moose     Open Access  
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Biology Teacher     Full-text available via subscription   (Followers: 14)
American Fern Journal     Full-text available via subscription   (Followers: 1)
American Journal of Agricultural and Biological Sciences     Open Access   (Followers: 9)
American Journal of Bioethics     Hybrid Journal   (Followers: 16)
American Journal of Human Biology     Hybrid Journal   (Followers: 18)
American Journal of Medical and Biological Research     Open Access   (Followers: 10)
American Journal of Plant Sciences     Open Access   (Followers: 21)
American Journal of Primatology     Hybrid Journal   (Followers: 16)
American Malacological Bulletin     Full-text available via subscription   (Followers: 3)
American Naturalist     Full-text available via subscription   (Followers: 81)
Amphibia-Reptilia     Hybrid Journal   (Followers: 6)
Anadol University Journal of Science and Technology B : Theoritical Sciences     Open Access  
Anadolu University Journal of Science and Technology : C Life Sciences and Biotechnology     Open Access   (Followers: 2)
Anaerobe     Hybrid Journal   (Followers: 4)
Anales de Biología     Open Access   (Followers: 3)
Analytical Methods     Full-text available via subscription   (Followers: 13)
Anatomical Science International     Hybrid Journal   (Followers: 3)
Animal Cells and Systems     Hybrid Journal   (Followers: 5)
Animal Models and Experimental Medicine     Open Access  
Annales de Limnologie - International Journal of Limnology     Hybrid Journal   (Followers: 1)
Annales françaises d'Oto-rhino-laryngologie et de Pathologie Cervico-faciale     Full-text available via subscription   (Followers: 3)
Annales Henri Poincaré     Hybrid Journal   (Followers: 3)
Annales Universitatis Mariae Curie-Sklodowska, sectio C – Biologia     Open Access   (Followers: 1)
Annals of Applied Biology     Hybrid Journal   (Followers: 8)
Annals of Biomedical Engineering     Hybrid Journal   (Followers: 19)
Annals of Human Biology     Hybrid Journal   (Followers: 6)
Annals of Science and Technology     Open Access  
Annual Research & Review in Biology     Open Access   (Followers: 2)
Annual Review of Biomedical Engineering     Full-text available via subscription   (Followers: 15)
Annual Review of Biophysics     Full-text available via subscription   (Followers: 26)
Annual Review of Cancer Biology     Full-text available via subscription   (Followers: 4)
Annual Review of Cell and Developmental Biology     Full-text available via subscription   (Followers: 42)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 15)
Annual Review of Genomics and Human Genetics     Full-text available via subscription   (Followers: 27)
Annual Review of Phytopathology     Full-text available via subscription   (Followers: 13)
Anthropological Review     Open Access   (Followers: 24)
Antibiotics     Open Access   (Followers: 9)
Antioxidants     Open Access   (Followers: 5)
Antioxidants & Redox Signaling     Hybrid Journal   (Followers: 9)
Antonie van Leeuwenhoek     Hybrid Journal   (Followers: 5)
Anzeiger für Schädlingskunde     Hybrid Journal   (Followers: 1)
Apidologie     Hybrid Journal   (Followers: 5)
Apmis     Hybrid Journal   (Followers: 2)
APOPTOSIS     Hybrid Journal   (Followers: 9)
Applied Biology     Open Access   (Followers: 2)
Applied Bionics and Biomechanics     Open Access   (Followers: 7)
Applied Vegetation Science     Full-text available via subscription   (Followers: 10)
Aquaculture Environment Interactions     Open Access   (Followers: 4)
Aquaculture International     Hybrid Journal   (Followers: 26)
Aquaculture Reports     Open Access   (Followers: 3)
Aquaculture, Aquarium, Conservation & Legislation - International Journal of the Bioflux Society     Open Access   (Followers: 7)
Aquatic Biology     Open Access   (Followers: 8)
Aquatic Ecology     Hybrid Journal   (Followers: 38)
Aquatic Ecosystem Health & Management     Hybrid Journal   (Followers: 16)
Aquatic Science and Technology     Open Access   (Followers: 4)
Aquatic Toxicology     Hybrid Journal   (Followers: 24)
Archaea     Open Access   (Followers: 4)
Archiv für Molluskenkunde: International Journal of Malacology     Full-text available via subscription   (Followers: 3)
Archives of Biological Sciences     Open Access  
Archives of Microbiology     Hybrid Journal   (Followers: 10)
Archives of Natural History     Hybrid Journal   (Followers: 8)
Archives of Oral Biology     Hybrid Journal   (Followers: 3)
Archives of Virology     Hybrid Journal   (Followers: 5)
Archivum Immunologiae et Therapiae Experimentalis     Hybrid Journal   (Followers: 2)
Arid Ecosystems     Hybrid Journal   (Followers: 3)
Arquivos do Instituto Biológico     Open Access   (Followers: 1)
Arquivos do Museu Dinâmico Interdisciplinar     Open Access  
Arthropod Structure & Development     Hybrid Journal   (Followers: 2)
Arthropods     Open Access   (Followers: 1)
Artificial DNA: PNA & XNA     Hybrid Journal   (Followers: 3)
Asian Bioethics Review     Full-text available via subscription   (Followers: 3)
Asian Journal of Biodiversity     Open Access   (Followers: 5)
Asian Journal of Biological Sciences     Open Access   (Followers: 3)
Asian Journal of Biology     Open Access   (Followers: 2)
Asian Journal of Biotechnology and Bioresource Technology     Open Access   (Followers: 1)
Asian Journal of Cell Biology     Open Access   (Followers: 6)
Asian Journal of Developmental Biology     Open Access   (Followers: 3)
Asian Journal of Medical and Biological Research     Open Access   (Followers: 5)
Asian Journal of Nematology     Open Access   (Followers: 4)
Asian Journal of Poultry Science     Open Access   (Followers: 5)
Atti della Accademia Peloritana dei Pericolanti - Classe di Scienze Medico-Biologiche     Open Access  
Australian Life Scientist     Full-text available via subscription   (Followers: 2)
Australian Mammalogy     Hybrid Journal   (Followers: 8)
Autophagy     Hybrid Journal   (Followers: 4)
Avian Biology Research     Full-text available via subscription   (Followers: 6)
Avian Conservation and Ecology     Open Access   (Followers: 15)
Bacterial Empire     Open Access   (Followers: 1)
Bacteriology Journal     Open Access   (Followers: 1)
Bacteriophage     Full-text available via subscription   (Followers: 3)
Bangladesh Journal of Bioethics     Open Access  
Bangladesh Journal of Plant Taxonomy     Open Access  
Bangladesh Journal of Scientific Research     Open Access   (Followers: 1)
Batman Üniversitesi Yaşam Bilimleri Dergisi     Open Access  
Berita Biologi     Open Access   (Followers: 1)
Between the Species     Open Access   (Followers: 1)
Bio Tribune Magazine     Hybrid Journal  
BIO Web of Conferences     Open Access  
BIO-Complexity     Open Access  
Bio-Grafía. Escritos sobre la Biología y su enseñanza     Open Access  
Bio-Lectura     Open Access  
BIO-SITE : Biologi dan Sains Terapan     Open Access   (Followers: 1)
Bioanalytical Reviews     Hybrid Journal   (Followers: 2)
Biocatalysis and Biotransformation     Hybrid Journal   (Followers: 6)
BioCentury Innovations     Full-text available via subscription   (Followers: 2)
Biochemistry and Cell Biology     Hybrid Journal   (Followers: 17)
Biochimie     Hybrid Journal   (Followers: 6)
BioControl     Hybrid Journal   (Followers: 6)
Biocontrol Science and Technology     Hybrid Journal   (Followers: 8)
Biodemography and Social Biology     Hybrid Journal  
BIODIK : Jurnal Ilmiah Pendidikan Biologi     Open Access   (Followers: 1)
BioDiscovery     Open Access   (Followers: 2)
Biodiversidade e Conservação Marinha : Revista CEPSUL     Open Access  
Biodiversitas : Journal of Biological Diversity     Open Access  
Biodiversity Data Journal     Open Access   (Followers: 4)
Biodiversity Informatics     Open Access   (Followers: 1)
Biodiversity Information Science and Standards     Open Access   (Followers: 2)
Biodiversity: Research and Conservation     Open Access   (Followers: 27)
Bioedukasi : Jurnal Pendidikan Biologi FKIP UM Metro     Open Access  
Bioeksperimen : Jurnal Penelitian Biologi     Open Access  
Bioelectrochemistry     Hybrid Journal   (Followers: 2)
Bioelectromagnetics     Hybrid Journal   (Followers: 2)
Bioenergy Research     Hybrid Journal   (Followers: 4)
Bioengineering and Bioscience     Open Access   (Followers: 3)
BioEssays     Hybrid Journal   (Followers: 11)
Bioethics     Hybrid Journal   (Followers: 18)
BioéthiqueOnline     Open Access  
Biofabrication     Hybrid Journal   (Followers: 5)
Biofilms     Full-text available via subscription   (Followers: 2)
Biogeosciences (BG)     Open Access   (Followers: 12)
Biogeosciences Discussions (BGD)     Open Access   (Followers: 3)

        1 2 3 4 5 6 7 8 | Last

Similar Journals
Journal Cover
Advances in Planar Lipid Bilayers and Liposomes
Journal Prestige (SJR): 0.109
Citation Impact (citeScore): 1
Number of Followers: 3  
  Full-text available via subscription Subscription journal
ISSN (Print) 1554-4516
Published by Elsevier Homepage  [3204 journals]
  • Series Page
    • Abstract: Publication date: 2015
      Source:Advances in Planar Lipid Bilayers and Liposomes, Volume 22

      PubDate: 2015-08-12T13:41:49Z
  • Stimuli-Sensitive Liposomes: Lipids as Gateways for Cargo Release
    • Authors: Mathias Viard; Anu Puri
      Abstract: Publication date: Available online 9 July 2015
      Source:Advances in Planar Lipid Bilayers and Liposomes
      Author(s): Mathias Viard , Anu Puri
      Lipids are integral part of cell membranes and play a vital role in biological processes such as membrane fusion, exocytosis, cell signaling, and disease progression. Uniquely defined chemical structures of lipids as well as their assembly in the aqueous environment are often known to dictate their biological activity. Some of these features of lipids have been exploited to develop carriers for drugs, bioactive molecules, and nucleic acids. Lipid-based nanocarriers (specifically liposomes) have claimed their status in the field of cancer nanomedicine. Liposomes, the longest studied nanocarriers (at least since four decades), are currently used in the clinics for delivery of drugs to treat certain types of cancers though not at their full potential. Further development in this field by utilizing site-specific targeting molecules and/or efforts to generate tunable liposomes can be predicted to enhance their suitability in the clinical settings. In general, the chemical and biophysical properties of lipid molecules primarily dictate the development of tunable (stimuli-sensitive) liposomes. Research activities toward stimuli-responsive liposomes can be broadly classified into internal (pH, redox, and enzyme) or external (heat, light and/or magnetic field, and ultrasound) stimulus. In this review, we will discuss the current status and latest developments in the field of stimuli-sensitive liposomes. The topics covered in this review will include (i) a brief summary of liposomes used in the clinics, stimuli-sensitive liposomes; (ii) triggering events by inclusion of coagents in the liposomes; (iii) triggering based on properties of lipids to yield heat, light, pH, redox, and enzyme-activatable liposomes; and (iv) limitations and future directions for the development of clinically viable stimuli-responsive liposomes.

      PubDate: 2015-07-10T09:02:36Z
  • Biomembrane Organization and Function: The Decisive Role of Ordered Lipid
    • Authors: Joaquim Catarina; A.C. Antunes Filipa Santos Rodrigo F.M. Almeida
      Abstract: Publication date: Available online 9 July 2015
      Source:Advances in Planar Lipid Bilayers and Liposomes
      Author(s): Joaquim T. Marquês , Catarina A.C. Antunes , Filipa C. Santos , Rodrigo F.M. de Almeida
      There has been a great effort to study lipid lateral organization in biomembranes in the past decades, in order to unravel the structural basis and functional significance of membrane lipid domains. However, in both respects fundamental doubts still persist, and recent results have widened this topic well beyond lipid rafts. In particular, the detection of sphingolipid-enriched gel domains in the yeast Saccharomyces cerevisiae plasma membrane, which are not the prototypical liquid ordered, sterol-enriched lipid rafts, will be described. The critical role of ordered lipid domains will be demonstrated with biophysical studies of membrane lipid organization in living cells and in model systems, concerning mammalian and fungal membranes. Membrane interactions with different types of bioactive molecules will be briefly presented, including endogenous molecules such as the hormone epinephrine or membrane proteins, as well as drugs, including anticancer and antitubercular compounds. Strategies to tackle the complexity of living cell membranes will be discussed, in an attempt to reach a compromise between lipid lamellar phases in artificial or reconstituted systems and observations in living cells. The development of new and improved biomimetic systems might provide answers to some of the open questions in the lipid domains field. Therefore, new lipid bilayer membrane models containing lipid domains stably formed on a conducting support (gold), where powerful surface and electrochemical techniques can be employed, will also be presented. The redox behavior of the catecholamine hormone epinephrine studied in such system showed that the lipid bilayer has a crucial role for the hormone chemical stability.

      PubDate: 2015-07-10T09:02:36Z
  • Membrane Microvesiculation and its Suppression
    • Authors: Veronika
      Abstract: Publication date: Available online 2 July 2015
      Source:Advances in Planar Lipid Bilayers and Liposomes
      Author(s): Veronika Kralj-Iglič
      Membrane microvesiculation is a common process in cells. Membrane constituents undergo lateral redistribution coupled to the change in local membrane curvature. Thin necks that are formed in this process can be torn by mechanical stress and membrane-enclosed fragments that contain various biologically active molecules become more or less free to move with fluids. Released vesicles are small in size (micrometer down to tens of nanometers). They interact with distant cells and thereby present an intercellular communication system which plays important physiological role in organisms. Micro and nanovesicles (NVs) can be isolated from body fluids. It was found that the concentration of NVs is increased in isolates from blood of patients with different diseases (e.g., cancer, inflammation, infection, thromboembolic diseases) indicating an increased vesiculability of blood cells. Here, we present some mechanisms of microvesiculation of biological membranes and suggest a possible mechanism for suppression of microvesiculation by a mediated attractive interaction between membranes.

      PubDate: 2015-07-06T05:12:09Z
  • Series Page
    • Abstract: Publication date: 2015
      Source:Advances in Planar Lipid Bilayers and Liposomes, Volume 21

      PubDate: 2015-04-02T02:50:56Z
  • Microscopy of Model Membranes: Understanding How Bcl-2 Proteins Mediate
    • Authors: Kushal Kumar; Das Joseph Unsay Ana Garcia-Saez
      Abstract: Publication date: Available online 7 February 2015
      Source:Advances in Planar Lipid Bilayers and Liposomes
      Author(s): Kushal Kumar Das , Joseph D. Unsay , Ana J. Garcia-Saez
      Apoptosis is a form of programmed cell death that plays an important role in key biological processes like development of organisms, the correct functioning of the immune system, and the maintenance of the cellular homeostasis. Dysregulation in the apoptotic pathway leads to diseases like cancer or neurodegenerative disorders. The proteins of the B-cell lymphoma 2 (Bcl-2) family are key regulators of mitochondrial outer membrane permeabilization (MOMP) during apoptosis, which is a critical step in the cell's commitment to death. However, their mechanism of action is still under intense investigation. Here, we discuss how microscopy approaches applied to model membranes are used to understand the intrinsic apoptotic pathway involving MOMP. We describe how model membranes mimicking the outer mitochondrial membrane (LUVs, GUVs, SLB) are used to understand the mechanism of Bcl-2-mediated apoptosis using state-of-the-art techniques like atomic force microscopy and fluorescence correlation spectroscopy. These studies have revealed interesting features like the role of membrane in altering the affinity of Bcl-2 proteins, Bax and Bak proapoptotic activity, mechanistic differences between pro- and antiapoptotic members, and the critical helices involved in pore formation by Bax.

      PubDate: 2015-02-12T01:36:21Z
  • Development of Polymer/Nanodiamond Composite Coatings to Control Cell
           Adhesion, Growth, and Functions
    • Authors: Milena Keremidarska; Kamelia Hristova; Todor Hikov; Ekaterina Radeva; Dimitar Mitev; Ivailo Tsvetanov; Radina Presker; Damjana Drobne; Barbara Drašler; Sara Novak; Veno Kononenko; Kristina Eleršič; Lilyana Pramatarova; Natalia Krasteva
      Pages: 1 - 26
      Abstract: Publication date: Available online 7 February 2015
      Source:Advances in Planar Lipid Bilayers and Liposomes
      Author(s): Milena Keremidarska , Kamelia Hristova , Todor Hikov , Ekaterina Radeva , Dimitar Mitev , Ivailo Tsvetanov , Radina Presker , Damjana Drobne , Barbara Drašler , Sara Novak , Veno Kononenko , Kristina Eleršič , Lilyana Pramatarova , Natalia Krasteva
      The identification of biomaterials that support appropriate cellular attachment, proliferation, and functions is critical for tissue engineering and cell therapy. There is a growing interest in functional organic/inorganic composites where a small amount of nanometer-sized material yields better physicochemical properties for cells to attach, grow, and differentiate. In this work, we prepared polymer/nanodiamond composite layers based on hexamethyldisiloxane and detonation-generated nanodiamond (DND) particles, in which the particles were either embedded into a polymer matrix or deposited on the preliminary formed plasma-polymerized (PP) layer. The surface properties of composites, such as roughness and wettability, as well as adhesion, growth, and functions of osteosarcoma MG-63 cells and primary rat mesenchymal stem cells were studied. We aimed to investigate the influence of the incorporation methods of DND into the polymer on the material surface properties and the cell response in order to control them by manipulating diamond-containing composite surfaces. We found differences between both composites in respect to their physicochemical properties and to the cell behavior suggesting that the method of particle incorporation into polymers should be taken in account during the development of new biomaterials for a specific application.

      PubDate: 2015-02-12T01:36:21Z
      DOI: 10.1016/bs.adplan.2015.01.001
  • Tethered Phospholipid Bilayer Membranes: An Interpretation of the
           Electrochemical Impedance Response
    • Authors: Gintaras Valincius; Mindaugas Mickevicius
      Pages: 27 - 61
      Abstract: Publication date: Available online 9 February 2015
      Source:Advances in Planar Lipid Bilayers and Liposomes
      Author(s): Gintaras Valincius , Mindaugas Mickevicius
      In this study, we discuss applications of the electrochemical impedance (EI) response of tethered bilayer membranes (tBLMs) in protein (peptide)/phospholipid membrane interaction studies. Because of highly asymmetric geometry, tBLMs exhibit unique EI response, which cannot be modeled by simple equivalent circuits consisting of capacitors and resistors. Special functions describe the characteristic features of EI spectra. They take into account the structural and the dielectric properties of the tBLMs. The analysis of the EI response provides the theoretical background for the utility of tBLMs as bioanalytical sensors for the membrane-damaging agents, such as pore-forming toxins. We demonstrate that the magnitude and frequency of the minimum of the negative of the phase as well as the modulus of impedance are the parameters indicative of the extent of the membrane damage and may be used to estimate the defect density in bilayers. The precision of such estimates is highly dependent on the knowledge of the physical properties of the submembrane reservoir separating phospholipid bilayer and solid surface. Clustering of the defects affects the EI response in a unique way, which may be used for the qualitative analysis of protein–membrane interactions.

      PubDate: 2015-02-12T01:36:21Z
      DOI: 10.1016/bs.adplan.2015.01.003
  • Effect of Lipid Bilayer Composition on Membrane Protein Association
    • Authors: Aiswarya B. Pawar; Xavier Prasanna; Durba Sengupta
      Pages: 43 - 63
      Abstract: Publication date: Available online 15 July 2015
      Source:Advances in Planar Lipid Bilayers and Liposomes
      Author(s): Aiswarya B. Pawar, Xavier Prasanna, Durba Sengupta
      Diverse cellular functions are supported by membrane protein assemblies associated with the cell membrane. Although considered to be protein-mediated, membrane components are now being recognized as critical in modulating and sometime dictating function. This chapter discusses the effect of the lipid bilayer, in particular its composition on membrane protein organization. Computational methods have been successful in quantifying transmembrane protein association and general features of dimerization profiles are explored. Understanding the molecular basis of the interactions has lead to the recognition of the lipophobic effects. These nonspecific effects include those that arise from membrane perturbations and lipid chain packing and have been shown to modulate the energetics as well as the structural characteristics of membrane protein dimerization. In addition, specific interactions arising from direct protein–lipid interactions and protein–cholesterol interactions have been suggested to influence membrane protein association. We summarize here a few examples highlighting the role of the lipid bilayer on membrane protein organization.

      PubDate: 2015-07-18T23:25:38Z
      DOI: 10.1016/bs.adplan.2015.06.001
  • Membrane-Bound Conformations of Antimicrobial Agents and Their Modes of
    • Authors: Upayan Baul; Satyavani Vemparala
      Pages: 97 - 128
      Abstract: Publication date: Available online 21 July 2015
      Source:Advances in Planar Lipid Bilayers and Liposomes
      Author(s): Upayan Baul, Satyavani Vemparala
      All antimicrobial agents are inherently membrane active and the complex interactions involved can lead to considerable conformational changes in the agents, while also inducing structural rearrangements of membrane lipids. Such structural modifications can trigger series of events enabling the agent to affect the structural integrity of the microbial membrane or translocate to the interior of the microbial cell. Therapeutic use of such agents requires a detailed understanding of the interaction of such antimicrobial agents with bacterial membranes. It is of interest to note that despite the existence of diversity in chemical compositions of many naturally occurring antimicrobial agents, the possible number of secondary structure conformations that they possess, either in solution or in membrane environment, is very small in number. In spite of considerable effort put in to probe the relationship between secondary structure and mode of antimicrobial action over the past two decades through experiments and simulations, a detailed understanding of the same is yet to be achieved. Furthermore, recent experimental and simulation results suggest that built-in well-defined secondary conformations such as α-helix or β-sheet may not be the essential feature of potent antimicrobial agents, but rather the ability of these agents to acquire amphiphilic conformations, involving the spatial separation of charged and hydrophobic moieties, near the bacterial membrane. In this chapter, we review different antimicrobial agents that have been the focus of various studies with special emphasis on computer simulations and their role in understanding the interactions of biomimetic antimicrobial polymers, based on methacrylate copolymers, with bacterial membranes.

      PubDate: 2015-07-23T03:19:29Z
      DOI: 10.1016/bs.adplan.2015.06.006
  • Optical Microscopy of Giant Vesicles as a Tool to Reveal the Mechanism of
           Action of Antimicrobial Peptides and the Specific Case of Gomesin
    • Authors: Karin A. Riske
      Pages: 99 - 129
      Abstract: Publication date: Available online 7 February 2015
      Source:Advances in Planar Lipid Bilayers and Liposomes
      Author(s): Karin A. Riske
      Antimicrobial peptides are part of the immune defense system involved in protection against pathogenic agents, such as bacteria and fungi. Most of them are cationic and amphipathic, an essential feature that confers them special affinity for their main target: the lipid matrix of the cell membrane of microorganisms. Their activity as biocides depends on perturbation of the membrane barrier, either by causing the opening of pores or by inducing membrane disintegration. Lipid bilayers have been widely used as biomimetic system of the complex cell membrane and were essential in providing mechanistic detail on the mode of action of antimicrobial peptides. In particular, giant unilamellar vesicles (GUVs) are cell-sized lipid vesicles that can be individually followed under a microscope, providing a direct way to correlate peptide binding with membrane permeabilization and domain formation. Here, an overview on the contributions of optical microscopy to reveal the mode of action of several membrane-active peptides is given and discussed. A complete characterization of the mechanism of action of the antimicrobial peptide gomesin from the Brazilian spider Acanthoscurria gomesiana developed by our group in recent works is presented, combining optical microscopy observation of GUVs and complementary techniques on large unilamellar vesicles, such as isothermal titration calorimetry, light scattering, and a leakage assay of an entrapped fluorescent dye.

      PubDate: 2015-02-12T01:36:21Z
      DOI: 10.1016/bs.adplan.2014.12.001
  • Phenomenology Based Multiscale Models as Tools to Understand Cell Membrane
           and Organelle Morphologies
    • Authors: Ramakrishnan Natesan; Ravi Radhakrishnan
      Pages: 129 - 175
      Abstract: Publication date: Available online 16 July 2015
      Source:Advances in Planar Lipid Bilayers and Liposomes
      Author(s): N. Ramakrishnan, Ravi Radhakrishnan
      An intriguing question in cell biology is “how do cells regulate their shape?” It is commonly believed that the observed cellular morphologies are a result of the complex interaction among the lipid molecules (constituting the cell membrane), and with a number of other macromolecules, such as proteins. It is also believed that the common biophysical processes essential for the functioning of a cell also play an important role in cellular morphogenesis. At the cellular scale—where typical dimensions are in the order of micrometers—the effects arising from the molecular scale can either be modeled as equilibrium or nonequilibrium processes. In this chapter, we discuss the dynamically triangulated Monte Carlo technique to model and simulate membrane morphologies at the cellular scale, which in turn can be used to investigate several questions related to shape regulation in cells. In particular, we focus on two specific problems within the framework of isotropic and anisotropic elasticity theories: namely, (i) the origin of complex, physiologically relevant, membrane shapes due to the interaction of the membrane with curvature remodeling proteins, and (ii) the genesis of steady state cellular shapes due to the action of nonequilibrium forces that are generated by the fission and fusion of transport vesicles and by the binding and unbinding of proteins from the parent membrane.

      PubDate: 2015-07-18T23:25:38Z
      DOI: 10.1016/bs.adplan.2015.06.004
  • Steric Stabilizers for Cubic Phase Lyotropic Liquid Crystal
           Nanodispersions (Cubosomes)
    • Authors: Josephine Y.T. Chong; Xavier Mulet; Ben J. Boyd; Calum J. Drummond
      Pages: 131 - 187
      Abstract: Publication date: Available online 4 February 2015
      Source:Advances in Planar Lipid Bilayers and Liposomes
      Author(s): Josephine Y.T. Chong , Xavier Mulet , Ben J. Boyd , Calum J. Drummond
      Lyotropic liquid crystalline nanostructured particles, such as cubosomes, have grown in popularity as drug delivery systems in the last few years. These systems require steric stabilizers to maintain colloidal stability in an aqueous medium, with Pluronic®F127, a block copolymer, being the most commonly employed stabilizer. However, in recent years, alternative, more effective stabilizers, as well as rationally designed systems with opportunities for further biofunctionalization have been reported. The purpose of this chapter is to collate and collectively interpret studies in the field of steric stabilization of this important emerging class of nanoparticles for drug and medical imaging agent delivery.

      PubDate: 2015-02-06T00:50:58Z
      DOI: 10.1016/bs.adplan.2014.11.001
  • Chapter Seven Probing the Self-Assembly of Unilamellar Vesicles Using
           Time-Resolved SAXS
    • Authors: Theyencheri Narayanan; Jeremie Gummel; Michael Gradzielski
      Pages: 171 - 196
      Abstract: Publication date: 2014
      Source:Advances in Planar Lipid Bilayers and Liposomes, Volume 20
      Author(s): Theyencheri Narayanan , Jeremie Gummel , Michael Gradzielski
      This chapter is aimed to provide an overview of recent experimental advances in the investigation of amphiphilic self-assembly processes in solution using time-resolved small-angle X-ray scattering combined with rapid stopped-flow mixing. The method is applicable to a broad range of self-assembly processes such as micellization, micelle–vesicle transition, micellar morphological transformations, and their inverse processes such as dissolution. The emphasis is on tracking the pathways of the self-assembly which could offer control over the process and predictive capabilities in terms of the thermodynamic parameters of the system. The examples presented here illustrate that self-assembly of unilamellar vesicles occurs via different routes depending on the concentration of initial surfactant solutions, disk-like or cylindrical intermediates are involved at higher concentration range, while torus-like intermediate structures are spontaneously formed in more dilute solutions. This demonstrates that the similar final structure of unilamellar vesicles can be reached by a variety of routes and the strong thermodynamic driving force for the formation of unilamellar vesicles in anionic–zwitterionic mixed surfactant systems.

      PubDate: 2014-07-25T22:47:58Z
      DOI: 10.1016/b978-0-12-418698-9.00007-1
      Issue No: Vol. 20 (2014)
  • Chapter Eight Defects in Planar Cell Polarity of Epithelium What Can We
           Learn from Liquid Crystals'
    • Authors: Rene Markovič; Marko Gosak; Robert Repnik; Samo Kralj; Marko Marhl
      Pages: 197 - 217
      Abstract: Publication date: 2014
      Source:Advances in Planar Lipid Bilayers and Liposomes, Volume 20
      Author(s): Rene Markovič , Marko Gosak , Robert Repnik , Samo Kralj , Marko Marhl
      Epithelial tissues are structured and highly organized monolayers of cells with many different tissue-specific functions. Ordering of epithelium cells in living tissues relies on spatially and temporally regulated cell behavior and is of vital importance for their functioning. The underlying mechanisms that govern the development of the tissue architecture and morphogenesis rely on planar cell polarity signaling pathways. Mutations and other disruptions of these pathways were found to cause developmental defects, leading to failures in lung branching or kidney development, for example, and are also involved in cancer cell migration. Here, we investigate how these defects affect the spatial arrangement and orientation of epithelium cells, giving special attention to tissue reorganization during development. For the characterization of the resulting polarized cytoarchitectures, we make use of methods developed in the field of liquid crystal (LC) research. In fact, epithelial tissues possess typical features of liquid crystalline systems albeit exhibiting a different local symmetry. Therefore, tools developed in the LC research community can be successfully applied for the description of the overall epithelial tissue topology and its orientational order. We additionally discuss and hypothesize the possibilities of using nanoparticles for structural defect stabilization and its application.

      PubDate: 2014-07-25T22:47:58Z
      DOI: 10.1016/b978-0-12-418698-9.00008-3
      Issue No: Vol. 20 (2014)
  • Chapter Two Cationic Liposomes as Model Nonviral Vectors for Pulmonary
           Delivery of DNA
    • Authors: Abdelbary Elhissi; Israr Ul Hassan; Antigoni Papapanou; Nimrah Zeb; Kevin M.G. Taylor
      Pages: 53 - 66
      Abstract: Publication date: 2014
      Source:Advances in Planar Lipid Bilayers and Liposomes, Volume 19
      Author(s): Abdelbary Elhissi , Israr Ul Hassan , Antigoni Papapanou , Nimrah Zeb , Kevin M.G. Taylor
      Gene therapy via inhalation is promising for the treatment of genetic-related diseases, such as cancer, immunological disorders, diabetes, and cystic fibrosis. However, delivery of gene without a suitable vector may result in poor cellular internalization and very low transfection rates. Nonviral vectors, such as cationic liposomes, are safer than viral vectors; hence, they have been investigated for gene delivery via nebulization. Tissue culture experiments have demonstrated that aerosolization produces higher gene transfection compared to fluid instillation. When considering the use of nebulizers for the delivery of cationic liposome–DNA formulations, gene expression was influenced by incubation time of DNA with cationic liposomes, lipid to DNA ratio, aerosol size distribution, composition of compressed gas used for nebulization, and the physiological condition of the lung. This chapter reviews the published literature in the field of pulmonary gene delivery using nebulizers and highlights the limitations of pulmonary delivery of genes. Novel approaches in gene therapy using RNA interference were also discussed.

      PubDate: 2014-04-18T16:15:35Z
      DOI: 10.1016/b978-0-12-418699-6.00002-3
      Issue No: Vol. 19 (2014)
  • Chapter Three Giant Unilamellar Vesicles and Suspended Nanobilayers as
           Model Systems for Biophysical Research
    • Authors: Oliver J. Pambos; Ulrich F. Keyser
      Pages: 67 - 89
      Abstract: Publication date: 2014
      Source:Advances in Planar Lipid Bilayers and Liposomes, Volume 19
      Author(s): Oliver J. Pambos , Ulrich F. Keyser
      Giant unilamellar vesicles (GUVs) and suspended lipid membranes are powerful biomimetic tools for studying a wide range of important biological functions such as membrane protein function, compartmentalization, lipid phase behavior, membrane mechanics, as well as many transmembrane transport processes fundamental to life. In the first part of this chapter, we outline the current approaches to GUV formation and their various applications in different areas of research. The second part introduces resistive pulse sensing, a technique central to the study of molecular transport across membranes, and finishes with a case study of a unique approach that uses GUVs to self-assemble suspended lipid membranes across glass nanopores. A final self-assembly process incorporates protein nanopores into this nanoscale lipid membrane allowing the detailed study of transmembrane transport in isolation and on a single-molecule level. This example demonstrates a simple, rapid, and low-cost route to the study of vitally important biological processes.

      PubDate: 2014-04-18T16:15:35Z
      DOI: 10.1016/b978-0-12-418699-6.00003-5
      Issue No: Vol. 19 (2014)
  • Chapter Six Biomimetic Liposome Model Systems to Study Cell Shape Control
           by the Cytoskeleton
    • Authors: Feng-Ching Tsai; Sophie Roth; Marileen Dogterom; Gijsje Hendrika Koenderink
      Pages: 139 - 173
      Abstract: Publication date: 2014
      Source:Advances in Planar Lipid Bilayers and Liposomes, Volume 19
      Author(s): Feng-Ching Tsai , Sophie Roth , Marileen Dogterom , Gijsje Hendrika Koenderink
      Shape changes of animal cells during cell division, migration, and tissue morphogenesis depend on an interplay between the plasma membrane and the cytoskeleton. The actin and microtubule cytoskeleton provide mechanical support to the plasma membrane but also exert active forces to deform the membrane. The molecular complexity of cells makes it difficult to dissect the mechanochemical interplay of the cytoskeleton and the plasma membrane in cell shape control. An increasingly popular approach is to reconstitute biomimetic model systems that can mimic a certain cellular function with a minimal set of purified cellular constituents. Such in vitro studies have provided many quantitative insights into the physical and biochemical properties of purified cytoskeletal polymers and model biomembranes in isolation. However, until now, there has been relatively little work on more complex and physiologically relevant model systems combining model biomembranes with cytoskeletal proteins. Here, we review methods designed to build biomimetic model cells consisting of cell-sized (10–50μm) liposomes encapsulating an actin or microtubule cytoskeleton. Moreover, we review recent results showcasing the reconstitution of increasingly complex model systems including physiological cytoskeleton–membrane linkers, nucleating factors, and molecular motors. Finally, we end with a short outlook providing ideas on future research directions.

      PubDate: 2014-04-18T16:15:35Z
      DOI: 10.1016/b978-0-12-418699-6.00006-0
      Issue No: Vol. 19 (2014)
  • Chapter Seven Role of Blood Sampling in Assessment of Concentration of
           Extracellular Nanovesicles in Isolates from Peripheral Blood
    • Authors: Roman Štukelj; Ines Hribar Ignaščenko; Sonja Peternelj; Magda Peruško; Tatjana Blažič; Manca Pajnič; Špela Bračun Vnuk; Vid Šuštar; Apolonija Bedina Zavec; Karin Schara; Rado Janša; Veronika Kralj-Iglič
      Pages: 175 - 189
      Abstract: Publication date: 2014
      Source:Advances in Planar Lipid Bilayers and Liposomes, Volume 19
      Author(s): Roman Štukelj , Ines Hribar Ignaščenko , Sonja Peternelj , Magda Peruško , Tatjana Blažič , Manca Pajnič , Špela Bračun Vnuk , Vid Šuštar , Apolonija Bedina Zavec , Karin Schara , Rado Janša , Veronika Kralj-Iglič
      Background: Cell-derived nanovesicles (NVs) are membrane-enclosed fragments of cell interior. They are formed in the last stage of membrane budding or in cell fragmentation. NVs are more or less free to move in body fluids and thereby constitute a cell–cell communication system. They can be harvested from body fluids, so they are potential novel biomarkers of health and disease. Advantages of NVs as biomarkers of disease are that they can be readily isolated from peripheral blood which can be obtained by phlebotomy. Blood sampling is minimally invasive while harvesting of NVs by centrifugation and washing of blood is a simple, low cost, and widely available method. Great promises of the method have, however, not yet been fulfilled, one of the reasons being poor repeatability and accuracy of the harvesting procedure. Aim: To study the effect of the blood sampling needles’ dimensions on the concentration of NVs in isolates from peripheral blood. Methods: Milliliters of blood were taken from an author with no record of disease into tubes containing trisodium citrate by a free flow. Sampling was performed 37 times by using 4 types of needles differing with respect to dimensions. The time of blood flow and the volume of the acquired blood were measured at the sampling. A mathematical model was applied assuming that the blood is a Newtonian fluid. The Navier–Stokes equation for flow through a narrow cylindrical tube was considered and the shear velocity at the needle inner wall was calculated. NVs were isolated from fresh blood by repetitive centrifugation and washing and counted by flow cytometry. Shear velocity at the tube wall was correlated with concentration of NVs in the isolates by the Pearson correlation coefficient (r) and the corresponding probability (p). Results: Results of mathematical models have shown that the shear stress depends on the length of the needle and its radius, or on the radius, the volume of the acquired blood, and on the time of the blood flow through the needle. We found a statistically significant correlation between the concentration of NVs in isolates and the calculated shear velocity of blood at the needle wall (r =0.56, p =0.004). Conclusions: It is indicated that the concentration of NVs in the isolates from blood is proportional to the shear velocity of blood during the flow through the needle. In order to minimize artefact NV production at sampling, the shear velocity should be minimized. This can be achieved by using long needle with small inner radius which, however, enables continuous blood flow.

      PubDate: 2014-04-18T16:15:35Z
      DOI: 10.1016/b978-0-12-418699-6.00007-2
      Issue No: Vol. 19 (2014)
  • Series Page
    • Abstract: Publication date: 2014
      Source:Advances in Planar Lipid Bilayers and Liposomes, Volume 20

      PubDate: 2014-07-25T22:47:58Z
  • Chapter One Biomimetic Membrane Supported at a Metal Electrode Surface A
           Molecular View
    • Authors: Jacek Lipkowski
      Abstract: Publication date: 2014
      Source:Advances in Planar Lipid Bilayers and Liposomes, Volume 20
      Author(s): Jacek Lipkowski
      This chapter reports on recent advances in the application of spectroscopic and surface imaging techniques to provide molecular level information about the structure of gold-supported phospholipid bilayers. It describes methods used to deposit biomimetic membrane at the gold electrode surface. It provides information about the structure of the membrane deposited at the gold electrode surface and its changes as a function of the applied potential obtained with the help of techniques such as scanning electron microscopy or atomic force microscopy, neutron reflectivity, and infrared reflection absorption spectroscopy. These experimental approaches provided unique molecular level information about the interactions of the membrane components with the metal, orientation, and conformation of molecules within the membrane, water content in the supported bilayer, and the structure of water molecules within the supported bilayer. The interactions of the bilayer with the metal restrict mobility of the membrane. From biomimetic point of view, this is an unwelcomed effect. However, the ability to immobilize phospholipid matrix on a conductive support provides unique opportunity to employ scanning tunneling microscopy to acquire molecular resolution images of channels formed by antibiotic peptides and in this way to provide direct evidence and molecular information of their action and their biocidal activity. The metal-supported model membranes find applications as biosensors. Proteins incorporated into such membranes constitute the sensing element and act as transducers of chemical to electrical information. This chapter includes a review of IRRAS studies of the potential induced changes in the orientation and conformation of membrane and peripheral proteins incorporated into the gold-supported bilayers.

      PubDate: 2014-07-25T22:47:58Z
  • Chapter Two Lipid Monolayers at the Air–Water Interface A Tool for
           Understanding Electrostatic Interactions and Rheology in Biomembranes
    • Authors: Natalia Wilke
      Abstract: Publication date: 2014
      Source:Advances in Planar Lipid Bilayers and Liposomes, Volume 20
      Author(s): Natalia Wilke
      Monomolecular films of surfactants at the air–water interface are easy to prepare and handle, and enable a broad variety of techniques to be used. As in other model systems mimicking membranes, two phases are observed in several experimental conditions. This chapter compares the results found using this model membrane with other models and describes some of the techniques applicable to lipid monolayers. The factors underlying their texture when two phases coexist are summarized, with special attention to line tension, an important parameter in both nucleation and growth, as well as the final domain shape. Finally, the effects of the presence of two phases on the observed mechanical properties of the film (elastic compressibility and shear viscosity) are detailed.

      PubDate: 2014-07-25T22:47:58Z
  • Chapter Three Langmuir–Blodgett Approach to Investigate Antimicrobial
           Peptide–Membrane Interactions
    • Authors: Sarah Dennison; Frederick Harris David Phoenix
      Abstract: Publication date: 2014
      Source:Advances in Planar Lipid Bilayers and Liposomes, Volume 20
      Author(s): Sarah R. Dennison , Frederick Harris , David A. Phoenix
      The ability of α-helical antimicrobial peptides to kill microorganisms depends upon their ability to interact with the membranes of these organisms. To be effective, such peptides require the ability to exhibit considerable discrimination between target and host cells. Key factors in selectivity and efficiency of action include differences between the phospholipid and sterol composition of the target membrane and host cell membrane. In this chapter, we present an overview of the Langmuir–Blodgett monolayers technique, which provides a versatile system for studying the interfacial properties of peptides and peptide–membrane interactions under controlled conditions. This system can provide information on the surface activity of peptides such as antimicrobial peptides and provide insights into their biological function at a membrane interface.

      PubDate: 2014-07-25T22:47:58Z
  • Chapter Four Divalent Metal Cations in DNA–Phospholipid Binding
    • Authors: Daniela
      Abstract: Publication date: 2014
      Source:Advances in Planar Lipid Bilayers and Liposomes, Volume 20
      Author(s): Daniela Uhríková
      Divalent metal cations are actively involved in cell's physiology and biochemistry. In addition to many others roles in cells, they mediate interaction between DNA and phospholipid bilayer. This chapter discusses the ability of divalent metal cations and phospholipid bilayers to condense DNA and to protect it against thermal denaturation. The microstructure of formed aggregates was studied using small-angle X-ray diffraction. Structural polymorphism induced by cations, ionic strength, and temperature generates a large variety of liquid-crystalline phases: condensed lamellar phases with or without DNA regular packing, coexistence of two lamellar phases, and also volume phases separation, which were identified in DNA-phopsholipid-cations mixtures. In addition to the alkaline earth metal cations, calcium and magnesium, transition metals (cobalt, manganese, nickel), and zinc are discussed as well.

      PubDate: 2014-07-25T22:47:58Z
  • Chapter Five Solid-Like Domains in Mixed Lipid Bilayers Effect of Membrane
           Lamellarity and Transition Pathway
    • Authors: Vernita Gordon; Paul Beales Gemma Shearman Zhijun Zhao John Seddon
      Abstract: Publication date: 2014
      Source:Advances in Planar Lipid Bilayers and Liposomes, Volume 20
      Author(s): Vernita D. Gordon , Paul A. Beales , Gemma C. Shearman , Zhijun Zhao , John M. Seddon , Wilson C.K. Poon , Stefan U. Egelhaaf
      We present optical observations of phase separation in mixed model membranes in the form of giant unilamellar vesicles. These observations are compared to the phase behavior of lipid mixtures, which we determined by X-ray scattering and differential scanning calorimetry or extracted from the existing literature. The domain properties are affected not only by the bulk phase behavior but also by the membrane lamellarity and phase transition pathways. These observations have important implications for how phase behavior determined by bulk methods using dense, multilamellar lipid bilayers are linked to phase separation in giant, unilamellar lipid bilayers as observed by microscopy.

      PubDate: 2014-07-25T22:47:58Z
  • Chapter Six Hexagonal Phase Formation in Oriented DPPC–Melittin Samples
           A Small-Angle X-ray Diffraction Study
    • Authors: Tanja Pott; Philippe
      Abstract: Publication date: 2014
      Source:Advances in Planar Lipid Bilayers and Liposomes, Volume 20
      Author(s): Tanja Pott , Philippe Méléard
      We investigated the influence of melittin on the organization of macroscopically oriented dipalmitoylphosphatidylcholine multilayers at 100% relative humidity as a function of temperature and peptide content by small-angle X-ray diffraction. Experiments were done under conditions known to lead to disk formation, a long-lived metastable state, below the transition temperature (T m), of the pure lipid and in excess water. For T > T m the system stays in a lamellar organization up to a lipid-to-peptide molar ratio, Ri , of 5, that is, the lowest Ri investigated herein. It was found that the macroscopically oriented system shows a rather complex behavior only below T m. For T < T m and for low peptide concentrations (Ri =200) formation of the rippled phase was found to be abolished. At Ri =100 melittin induces the formation of a rippled phase at relative low temperature (29°C). At higher peptide content and T < T m melittin induces the formation of a hexagonal phase, presumably metastable, in coexistence with a lamellar gel phase. A parallel is made with the well-known disk formation. An interpretation in terms of mismatch between the length of the peptide helix and the bilayer thickness is proposed.

      PubDate: 2014-07-25T22:47:58Z
  • Chapter Five Structural Transitions in Lipid Membranes Mechanism for
           Cell-Penetrating Peptides
    • Authors: Abhijit Mishra
      Abstract: Publication date: 2014
      Source:Advances in Planar Lipid Bilayers and Liposomes, Volume 19
      Author(s): Abhijit Mishra
      Cell-penetrating peptides are short cationic peptides that have the ability to translocate efficiently across the plasma membranes of most eukaryotic cells. Successful intracellular delivery of many biologically active molecules has been possible using these peptides. However, the exact molecular mechanism of entry remains elusive. Many different mechanisms, including direct translocation and various endocytotic pathways, have been proposed but how a relatively short peptide facilitates these effects is unknown. Here, we review the various proposed mechanisms and note that the complete CPP behavior is not fully explained. We examine how peptides interact with lipid membranes using small-angle X-ray scattering and confocal microscopy and show that CPPs induce negative Gaussian curvature, the type of curvature observed in membrane-destabilizing processes like poration, invaginations, and protrusions. We further show how CPPs can multiplex interactions with different cellular components to facilitate cellular uptake of small proteins to large nanoparticles.

      PubDate: 2014-04-23T11:23:54Z
  • Series Page
    • Abstract: Publication date: 2014
      Source:Advances in Planar Lipid Bilayers and Liposomes, Volume 19

      PubDate: 2014-04-18T16:15:35Z
  • Chapter One Charged Particles can Mediate Attraction Between Equally
           Charged Membranes—Theoretical Study
    • Abstract: Publication date: 2014
      Source:Advances in Planar Lipid Bilayers and Liposomes, Volume 19
      Author(s): Šárka Perutková
      Electrostatic interactions are one of the leading interactions in all biological systems. In this chapter, we present a possible mechanism which can lead to attractive interaction between two like-charged biological surfaces. We show three different modeled systems of charged biological surfaces in the solution containing charged macro-ionic particles which were inspired by experimental observations. In our proposed mechanism, we take into consideration the orientational entropy of the system. Namely, when the macro-ionic particles in solution have distinctive internal distribution of charge, the additional degrees of freedom for rotation are involved in the entropic contribution to the total free energy. The contribution is negative and thus lowers the free energy. Under certain conditions, this can lead to attractive force between like-charged surfaces. In the study, we use analytical as well as numerical methods—modifications of Poisson–Boltzmann equation and Monte Carlo simulations. We studied rod-like and spherical geometry of particles which can mediate the attraction. The macro-ionic particles can represent different kinds of proteins or various metallic nanoparticles in aqueous surrounding.

      PubDate: 2014-04-18T16:15:35Z
  • Chapter Four Hydrophobically Modified Chitosan Solution Properties by
           Rheology and Light Scattering
    • Authors: Aarti Shedge; Manohar Badiger
      Abstract: Publication date: 2014
      Source:Advances in Planar Lipid Bilayers and Liposomes, Volume 19
      Author(s): Aarti S. Shedge , Manohar V. Badiger
      Hydrophobically modified chitosan was prepared using the hydrophobic compound derived from natural resource material such as cashew nut shell liquid. Chitosan was modified using 3-pentadecyl cyclohexane carbaldehyde to different extents (2, 3, and 5mol%). Solution properties of hydrophobically modified chitosan were studied by rheology and light scattering. These indicated the aggregation behavior above the critical association concentration. Further, it was concluded that above the critical association concentration, the dynamics of the network formed due to the associations slowed down significantly.

      PubDate: 2014-04-18T16:15:35Z
  • Series Page
    • Abstract: Publication date: 2013
      Source:Advances in Planar Lipid Bilayers and Liposomes, Volume 18

      PubDate: 2013-08-31T06:15:42Z
  • Chapter One Charged Lipid Bilayers in Aqueous Surroundings with Low pH
    • Abstract: Publication date: 2013
      Source:Advances in Planar Lipid Bilayers and Liposomes, Volume 18
      Author(s): Denitsa Mitkova , Angelina Stoyanova-Ivanova , Stela Georgieva , Petar Todorov , Nikolay Kozarev , Yury A. Ermakov , Victoria Vitkova
      The present chapter discusses our experimental results on morphology, stability, and the mechanical properties of two-component charged lipid bilayers in aqueous solutions with controlled ionic strength at low pH. Observations by phase-contrast and fluorescent microscopy revealed coexistence of two structural phases in membranes from stearoyl oleoyl phosphatidylcholine (SOPC), containing more than 10mol% of the charged lipid dioleoyl phosphatidylserine. At temperatures lower than 29°C, the existence of nonfluctuating “hard” domains was registered in fluid membranes at pH 5.0. The method of shape-fluctuation analysis of quasi-spherical vesicles was applied for the determination of the bending modulus of homogeneous liquid bilayers. The value obtained for this material constant of bilayers with 0.2 molar fraction of charged lipid is around 30% higher than the bending modulus of uncharged (SOPC) membranes in the same surrounding solution. The experimental findings, presented and discussed in the chapter, qualitatively agree with our previous results for the curvature rigidity of charged bilayers as measured by vesicle micromanipulation.

      PubDate: 2013-08-31T06:15:42Z
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