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Annual Reports on NMR Spectroscopy

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ISSN (Print) 0066-4103
Published by Elsevier

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Chapter Four NMR Studies of Molten Salt and Room Temperature Ionic Liquids
- Abstract: 2013
  Publication year: 2013
  Source:Annual Reports on NMR Spectroscopy, Volume 78
  
  This chapter presents the nuclear magnetic resonance (NMR) developments and studies on the high temperature inorganic molten salts and on room temperature ionic liquids. It is focused on the liquid structure investigated, thanks to the chemical shifts analysis and to magnetization transfer experiments. It deals also with the dynamics at the local scale investigated using relaxometry and at the long range using pulsed field gradient NMR.
  
  PubDate: 2013-02-22T22:14:15Z
Chapter Five Intermolecular Zero Quantum Coherence in NMR Spectroscopy
- Abstract: 2013
  Publication year: 2013
  Source:Annual Reports on NMR Spectroscopy, Volume 78
  
  Intermolecular zero-quantum coherences (iZQCs) originating from distant dipolar interactions between spins in different molecules provide an innovative way for nuclear magnetic resonance (NMR) spectroscopy. Since the field experienced by iZQC signals is in the dipolar correlation distance, it is naturally to apply iZQCs for resolution enhancement in NMR spectroscopy, especially under the spatially and/or temporally varying magnetic fields. Two theoretical frames, classical distant dipolar field and quantum-mechanical intermolecular multiple-quantum coherence treatments, are available for the description of iZQC signal evolution. A variety of iZQC spectroscopic techniques have been established and most of them take advantage of two-dimensional acquisition to recover a one-dimensional high-resolution spectrum with information on chemical shifts, relative peak areas, J-coupling constants, and multiplet patterns. In this review, two comprehensive descriptions of an iZQC signal are presented first. The existing iZQC techniques are then systematically described. The details and underlying mechanisms of these techniques are discussed. Finally, the in vivo applications of iZQC spectroscopic techniques are given.
  
  PubDate: 2013-02-22T22:14:15Z
Chapter Two Applications of Projection NMR Techniques
- Abstract: 2013
  Publication year: 2013
  Source:Annual Reports on NMR Spectroscopy, Volume 78
  
  Among the range of fast methods that were developed for speeding up NMR data acquisition, mostly over the last decade, projection spectroscopy and reduced dimensionality approaches have found significant area of applications in both solution and solid-state NMR studies. In this review, we illustrate the diversity of these applications, notably in the field of biomolecular NMR. Projection spectroscopy plays a remarkable role in the modern protocols for backbone and side-chains assignment for high-throughput structural studies of small globular proteins, or for investigations of macromolecular systems exhibiting high chemical shift degeneracy. Approaches that exploit projection spectroscopy and reconstruction approaches for structural investigations of small molecules and their complex mixtures, as well as high-resolution studies of materials in the solid-state are also presented.
  
  PubDate: 2013-02-22T22:14:15Z
Chapter Three Optical Atomic Magnetometry for Ultra-Low-Field NMR Detection
- Abstract: 2013
  Publication year: 2013
  Source:Annual Reports on NMR Spectroscopy, Volume 78
  
  This chapter deals with detection of nuclear magnetic resonance (NMR) signals in the ultra-low-field (ULF) regime, by means of optical atomic magnetometers (OAMs). A general introduction is provided about specific NMR features occurring when nuclei precess in microtesla fields, or weaker. The advantages of detecting the NMR signal by means of an OAM are here preliminarily discussed. A further general introduction is provided about basic ideas and recent progresses in optical atomic magnetometry. A section is devoted to the detailed presentation of an example of dual-channel atomic magnetometer which was used to detect the signal produced by protons of a remotely polarized water sample in an unshielded environment, taking advantage of its differential nature. Results reported in a wide set of similar experiments are then discussed in a general synthesis of the interdisciplinary activity performed on the main subject of this work. We report on progresses made in the ULF-NMR applications in imaging, microfluidic, zero- and near-zero field spectroscopy. The non-conventional NMR detection schemes discussed in this chapter are in some cases profitably coupled with non-conventional methods for sample polarization. Some experiments devoted to non-conventional preparation of the nuclear spin state are considered and briefly discussed, as well.
  
  PubDate: 2013-02-22T22:14:15Z
Index
- Abstract: 2013
  Publication year: 2013
  Source:Annual Reports on NMR Spectroscopy, Volume 78
  
  PubDate: 2013-02-22T22:14:15Z
Contributors
- Abstract: 2013
  Publication year: 2013
  Source:Annual Reports on NMR Spectroscopy, Volume 78
  
  PubDate: 2013-02-22T22:14:15Z
Preface
- Abstract: 2013
  Publication year: 2013
  Source:Annual Reports on NMR Spectroscopy, Volume 78
  
  PubDate: 2013-02-22T22:14:15Z
Chapter One Recent Advances of Solid-State NMR Studies on Zeolites
- Abstract: 2013
  Publication year: 2013
  Source:Annual Reports on NMR Spectroscopy, Volume 78
  
  Solid-state nuclear magnetic resonance (NMR) is a well-established tool for the structural characterization and dynamics study of various multifunctional materials. This review intends to cover the recent process for versatile solid-state NMR studies of topology structures, crystallization processes, host–guest interactions, acidities and catalytic reaction mechanisms of various zeolites. New insights into the relationship between zeolite structures and properties at the atomic level could benefit a lot from the new developments of solid-state NMR methodology and density functional theoretical (DFT) calculation. The spatial connections, distance information and anisotropic chemical shifts of silicon sites determined by 29Si magic angle spinning (MAS) NMR can serve as structural constraints to resolve the topology structure of zeolites. 129Xe NMR can be employed to investigate the cage and channel structure and communication in zeolites. The host–guest interactions between zeolite frameworks and confined molecules have been characterized by two-dimensional heteronuclear correlation experiments. The acidity property of zeolites (including acid type, strength, concentration as well as distribution) can be well understood through the combination of solid-state NMR probe molecule technique and DFT calculation. In particular, information about spatial proximities among various acid sites in zeolites is available from two-dimensional double quantum MAS NMR experiments. The crystallization and catalytic reaction mechanisms can be elucidated by monitoring the evolution of crystallization and reaction processes, respectively, through solid-state NMR spectroscopy.
  
  PubDate: 2013-02-22T22:14:15Z
Copyright
- Abstract: 2013
  Publication year: 2013
  Source:Annual Reports on NMR Spectroscopy, Volume 78
  
  PubDate: 2013-02-22T22:14:15Z
Chapter 3 Solution-State Dynamic Nuclear Polarization
- Abstract: 2011
  Publication year: 2011
  Source:Annual Reports on NMR Spectroscopy, Volume 73
  
  Solution-state dynamic nuclear polarization (DNP) is an increasingly popular method of enhancing nuclear spin polarization that has many applications in nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI). The theory, methods and applications of DNP in the solution state using the Overhauser effect are distinctly different from those of solid-state DNP or what is known as dissolution DNP. This review discusses the theory and recent experimental advances of Overhauser DNP techniques in the solution state at various field strengths ranging from the earth's magnetic field to 9.2T, covering the literature from 1986 to late 2010. Most of the focus in this review is on spectroscopy applications of DNP, although proton–electron double resonance imaging (PEDRI) and remotely enhanced liquids for imaging contrast (RELIC) applications are briefly covered.
  
  PubDate: 2012-12-16T09:05:37Z
Preface
- Abstract: 2011
  Publication year: 2011
  Source:Annual Reports on NMR Spectroscopy, Volume 73
  
  PubDate: 2012-12-16T09:05:37Z
Chapter 1 Recent Progress in the Solid-State NMR Studies of Biomineralization
- Abstract: 2011
  Publication year: 2011
  Source:Annual Reports on NMR Spectroscopy, Volume 73
  
  Biomineralization is a challenging research area because it is extremely difficult to study the interaction between two dissimilar organic and inorganic nanophases. In this review, we have briefly discussed some advanced solid-state NMR techniques developed for the study of biominerals or related in vitro model systems. The P-31 NMR parameters of a list of model compounds have been compiled. These data should be useful for analyzing the NMR spectra of biominerals. We intend to provide an account of how one can employ the state-of-the-art solid-state NMR techniques to extract valuable structural information of biominerals that would be difficult to obtain otherwise.
  
  PubDate: 2012-12-16T09:05:37Z
Chapter 2 Recent Advances in the NMR Spectroscopy of Chlorine, Bromine and Iodine
- Abstract: 2011
  Publication year: 2011
  Source:Annual Reports on NMR Spectroscopy, Volume 73
  
  This review is a comprehensive overview of the advances in the nuclear magnetic resonance spectroscopy of chlorine, bromine and iodine nuclei, with the former two being focused upon. A recent review specifically dealing with the solid state nuclear magnetic resonance (SS NMR) of these halogens was published in 2006 [D. Bryce and G. Sward, Magn. Reson. Chem., 2006, 44, 409–450.], with an update in 2009 [C. M. Widdifield, R. P. Chapman and D. L. Bryce, Annu. Rep. NMR Spectrosc., 2009, 66, 195–326.]. This review will cover work in this area subsequent to the material already presented, including all work up until and including September 2010. In addition, the use of chlorine, bromine and iodine NMR spectroscopy in the solution state over the past 10 years is covered with emphases on its development and application. Recent advancements in instrumental and analytical techniques are analysed in order to view their impact on the use of these particular halogens in NMR spectroscopy.
  
  PubDate: 2012-12-16T09:05:37Z
Chapter 7 Highly Customized NMR Systems Using an Open-Resource, Home-Built Spectrometer
- Abstract: 2011
  Publication year: 2011
  Source:Annual Reports on NMR Spectroscopy, Volume 74
  
  An integrated Field-Programmable Gate Array (FPGA)-based NMR spectrometer is described, with an emphasis on its applications to non-conventional NMR experiments, some of which are accompanied with modification to the hardware and software of the system.
  
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Index
- Abstract: 2011
  Publication year: 2011
  Source:Annual Reports on NMR Spectroscopy, Volume 74
  
  PubDate: 2012-12-16T09:05:37Z
Copyright
- Abstract: 2011
  Publication year: 2011
  Source:Annual Reports on NMR Spectroscopy, Volume 73
  
  PubDate: 2012-12-16T09:05:37Z
Contributors
- Abstract: 2011
  Publication year: 2011
  Source:Annual Reports on NMR Spectroscopy, Volume 73
  
  PubDate: 2012-12-16T09:05:37Z
Chapter 6 Recent Developments in HMBC Studies
- Abstract: 2011
  Publication year: 2011
  Source:Annual Reports on NMR Spectroscopy, Volume 74
  
  Since its introduction, the HMBC—Heteronuclear Multiple Bond Correlation—experiment has modernized NMR spectroscopy in small to medium molecule applications. The experiment provides information about which protons are near to different carbons or to another heteronucleus, but not directly bonded to. This experiment can provide a huge amount of information about molecular structure, since the long-range proton–carbon correlations can include quaternary carbons, in addition to protonated carbons. Impressive examples for structure elucidation of organic molecules, peptides, or natural products have been published in the last 20 years. After a short introduction into the basic theory, this manuscript will give to the reader an overview of the last developments and improvements of HMBC experiments, ranging from pulse sequences dedicated for suppressing one-bond correlations to HMBC pulse sequences that allow distinguishing between 2 J CH and 3 J CH cross-peaks.
  
  PubDate: 2012-12-16T09:05:37Z
Chapter 4 Probing Interactions Between Small Molecules and Polymers by Means of NMR Spectroscopy
- Abstract: 2011
  Publication year: 2011
  Source:Annual Reports on NMR Spectroscopy, Volume 74
  
  Interactions between small molecules and polymers, or species with a biological relevance as proteins and enzymes, are of high significance in several research fields, above all physics, chemistry, biology and medicine. The type and the strength of the interactions rule most of the occurring processes and determine the main characteristics of the systems. Drug-receptor, signal transduction, cellular recognition are only a few examples of binding phenomena where a profound understanding of the interaction is indispensable. In the next pages, a brief overview of known application of NMR spectroscopy for assessing interactions between small molecules and polymers is reported with the aim of underlying the importance of NMR in this research area.
  
  PubDate: 2012-12-16T09:05:37Z
Chapter 5 Using 1,1- and 1,n-ADEQUATE 2D NMR Data in Structure Elucidation Protocols
- Abstract: 2011
  Publication year: 2011
  Source:Annual Reports on NMR Spectroscopy, Volume 74
  
  Modern structure elucidation methods are heavily reliant on a variety of two-dimensional NMR methods. Direct heteronuclear shift correlation methods via 1 J XH and long-range correlation methods via n J XH, in particular, have become the cornerstone of modern structure elucidation protocols. Unfortunately, the inherent ambiguity in the number of bonds across which long-range heteronuclear correlations are observed can complicate the determination of novel structures, even leading in some cases to erroneously reported structures. Various NMR experiments have been devised to circumvent problems inherent to the interpretation of long-range heteronuclear correlation methods; the 1,1- and 1,n-ADEQUATE experiments are among the methods developed. The 1,1- and 1,n-ADEQUATE experiments begin with an initial 1 J CH transfer of magnetization followed by either a 1 J CC or n J CC carbon–carbon transfer, respectively, in an out-and-back sense. Thus, the 1,1-ADEQUATE experiment provides exclusively the identity of protonated and non-protonated carbons that are adjacent to the proton–carbon pair involved in the initial one-bond heteronuclear transfer. The 1,n-ADEQUATE experiment correspondingly provides long-range carbon–carbon connectivity information, primarily via 3 J CC although 2 J CC correlations are observed in some cases. The acquisition and interpretation of 1,1- and 1,n-ADEQUATE spectra are discussed in addition to the much less frequently utilized n,1- and n,m-ADEQUATE experiments. Applications of these experiments found in the literature through early 2011 are surveyed. Finally, the utilization of the newly developed unsymmetrical and generalized indirect covariance processing methods to calculate HSQC-1,1- and HSQC-1,n-ADEQUATE spectra is also discussed. These processing methods afford a convenient, diagonally symmetric carbon–carbon correlation spectrum in addition to allowing sample sizes, and/or data acquisition times to be reduced through the five- to as much as twentyfold gain in sensitivity inherent to the covariance processing method. Examples are shown and the interpretation of these data is also discussed.
  
  PubDate: 2012-12-16T09:05:37Z
Chapter 2 Carbon-13 Heteronuclear Longitudinal Spin Relaxation for Geometrical (and Stereochemical) Determinations in Small or Medium Size Molecules
- Abstract: 2011
  Publication year: 2011
  Source:Annual Reports on NMR Spectroscopy, Volume 74
  
  Owing to an extremely abundant literature making use of spin relaxation for structural studies, this review is limited to carbon-13 spectroscopy, to small or medium size molecules, to stereochemical and preferably geometrical determinations. The parameter of choice is evidently the Nuclear Overhauser effect (NOE) because it depends exclusively on the dipolar interaction mechanism, thus on 1/r 6, where r is the distance between the two interacting spins. However, it depends also on the dynamical features of the system under investigation which must be characterized prior to any attempt for obtaining geometrical or stereochemical information. Therefore, this review is devoted not only to 1H–13C NOE but, more generally, to 13C longitudinal relaxation. After comprehensive theoretical developments, experimental methods presently available will be presented. The latter include the usual gated decoupling experiment and pulse experiments of the HOESY (Heteronuclear Overhauser Effect SpectroscopY) family. These pulse experiments, which imply carbon-13 observation, can be one-dimensional, selective one-dimensional or two-dimensional. The emphasis will be put on the interpretation which is different according to the occurrence or not of extreme narrowing conditions. Along with a literature survey, some selected examples will be presented in detail in order to illustrate the potentiality of the method.
  
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Chapter 3 NMR Studies of Optically Active Schiff Bases
- Abstract: 2011
  Publication year: 2011
  Source:Annual Reports on NMR Spectroscopy, Volume 74
  
  The review covers the use of NMR spectroscopy in studies of optically active Schiff bases based on selected results reported in the last decade. The first part of the review is devoted to formation of Schiff bases as products which facilitate determination of the enatiomeric purity of various compounds. The next part is dedicated to conformational studies and investigation of different types of equilibria in optically active Schiff bases. Another part is devoted to studies of selected metal complexes, derivatives of optically active Schiff bases. Results concerning investigation of biologically active compounds in which Schiff bases are formed as intermediate product of enzymatic reactions are presented in separate section.
  
  PubDate: 2012-12-16T09:05:37Z
Preface
- Abstract: 2011
  Publication year: 2011
  Source:Annual Reports on NMR Spectroscopy, Volume 74
  
  PubDate: 2012-12-16T09:05:37Z
Chapter 1 NMR Studies on Structurally or Dynamically Heterogeneous Systems Dynamic Aspects of Hydrogels, Protein Fibrils and Membrane Proteins
- Abstract: 2011
  Publication year: 2011
  Source:Annual Reports on NMR Spectroscopy, Volume 74
  
  There are a variety of macromolecular systems exhibiting structural and dynamic heterogeneity, in which expected NMR signals are not always fully visible by a single set of NMR measurements. The former includes hydrogels of synthetic polymers, polysaccharides, and aggregated proteins, the latter of which can be further converted to amyloids or prions. They are very important as materials for biomedical or industrial applications, a variety of biological functions including host-defence systems, components of biological tissues, or key substances leading to several serious diseases. In addition, membrane proteins are typical dynamically heterogeneous systems which give rise to suppressed peaks depending upon local protein dynamics. In particular, it is emphasized that the presence of such suppressed peaks affords an invaluable means to determine their dynamic information. In this chapter, we first briefly review several parameters to be able to analyse their dynamic features. Then, we discuss two types of heterogeneous systems in more detail: structurally and/or dynamically heterogeneous systems. NMR studies on synthetic and polysaccharide gels and protein fibrils are reviewed with emphasis on revealing their secondary structures and dynamic aspects. Dynamic aspects of membrane proteins are also discussed in relation to their biological function. It turned out that the combined use of a solution (and or solution-like) state and a solid-state NMR technique are essential to be able to fully observe signals from portions of different mobility. We emphasize that recording spectra based on dipolar decoupled (or the direct detection) magic angle spinning (DDMAS) approach is essential to be able to reveal the more flexible portions of these systems, because the conventional solid-state NMR, using cross-polarization magic angle spinning (CPMAS) alone, is not sufficient for detecting signals from the solid-like portions.
  
  PubDate: 2012-12-16T09:05:37Z
Index
- Abstract: 2012
  Publication year: 2012
  Source:Annual Reports on NMR Spectroscopy, Volume 75
  
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Copyright Page
- Abstract: 2011
  Publication year: 2011
  Source:Annual Reports on NMR Spectroscopy, Volume 74
  
  PubDate: 2012-12-16T09:05:37Z
Contributors
- Abstract: 2011
  Publication year: 2011
  Source:Annual Reports on NMR Spectroscopy, Volume 74
  
  PubDate: 2012-12-16T09:05:37Z
Chapter 3 Methods and Applications of Phosphorus NMR Spectroscopy In Vivo
- Abstract: 2012
  Publication year: 2012
  Source:Annual Reports on NMR Spectroscopy, Volume 75
  
  Phosphorus-31 MRS is one of the earliest in vivo MRS methods. It was widely employed by the MR community even before the advent of clinical MRI and is an excellent technique to study in vivo metabolism associated with bioenergy and cell membranes. During its almost 40 years practice in in vivo research, there have been many reviews. In this review, we focus on the past 5 years of research applications and development, based on a PUBMED search using the keywords “phosphorus-31 OR 31P” and “MRS”. In addition to reporting the current trend of 31P MRS technical development, we also emphasize its application in biomedical research, particularly in disease diagnosis and biomarkers. We also give brief comments on the future direction of in vivo 31P MRS.
  
  PubDate: 2012-12-16T09:05:37Z
Chapter 4 Compact Superconducting Magnet Design for Nuclear Magnetic Resonance The Minimum Stored Energy Approach
- Abstract: 2012
  Publication year: 2012
  Source:Annual Reports on NMR Spectroscopy, Volume 75
  
  Superconducting magnet coil arrangements applicable in nuclear magnetic resonance across a range of magnetic field strengths are described in the context of the minimum stored energy (MSE) design. The approach is based on first calculating an optimal current density map, which is then used to allocate coils for the second stage of the optimization process. Having stated the coil domain, required magnetic field strength and constraint of current density, a set of superconducting magnet coil arrangements can be computed. Low- and high-field magnet coils achieving field strengths of 1, 3, 7 and 11.75T are provided for the cylindrical compact designs, 1T for the asymmetric coil arrangement and 1T for the open double-doughnut configuration magnet. Irrespective of the magnet type, our findings show that individual magnet coils should be arranged at the local positive maxima and negative minima of the current density map and around the perimeter of the domain used to specify possible coil locations. Moreover, at high-field, which we assume to be larger than 3T, the maximum fields are located on coils with the smallest radii, whereas at low-field, this is not the case. This becomes a critical observation for high-field applications, as the superconducting magnet design freedom is restricted by inherent peak field limits on superconductors. To reduce the peak field experienced by any coil, the domain has to be made longer, resulting in physically large magnets. Our findings also suggest that at low-field, reverse current coils can be employed to shorten the length of the magnet. When the field strengths is greater than 3T, large peak fields produced between adjacent coils with alternating currents limit the ability to incorporate reverse current coils without a breach of the peak field limit.
  
  PubDate: 2012-12-16T09:05:37Z
Preface
- Abstract: 2012
  Publication year: 2012
  Source:Annual Reports on NMR Spectroscopy, Volume 75
  
  PubDate: 2012-12-16T09:05:37Z
Chapter 1 Constant Time REDOR NMR Spectroscopy
- Abstract: 2012
  Publication year: 2012
  Source:Annual Reports on NMR Spectroscopy, Volume 75
  
  The constant time version of rotational echo double resonance (CT-REDOR) may be applied as an expedient alternative to the existing REDOR versions in cases in which strong heteronuclear dipolar couplings severely complicate the data analysis and render an accurate determination of the second moments impossible. The various facets of CT-REDOR are outlined and the applicability of the presented approaches exemplified on model compounds. For short dipolar evolution times, accurate values for the second moments can be obtained without the need to incorporate the full information about the detailed spin geometry of the multiple-spin systems into the simulation protocol.
  
  PubDate: 2012-12-16T09:05:37Z
Chapter 2 Recent Advances in Solid-State 25Mg NMR Spectroscopy
- Abstract: 2012
  Publication year: 2012
  Source:Annual Reports on NMR Spectroscopy, Volume 75
  
  In spite of the relatively unfavourable characteristics of the 25Mg nuclide for NMR experiments—such as low natural abundance, small magnetogyric ratio and sizeable quadrupolar broadening—there is increasing evidence that solid-state 25Mg NMR is a powerful tool for studies involving many different materials. Much of the recent boost in this field has been driven by instrumental improvements, such as the availability of high magnetic fields and fast-spinning speeds, as well as by the use of signal-enhancement methods developed in the past decade for half-integer spin quadrupolar nuclei. The most relevant advances in solid-state 25Mg NMR spectroscopy are reviewed here, including a detailed account of the use of signal-enhancement methods and of the more recent applications of first-principles calculations of 25Mg NMR parameters. Examples of the application of 25Mg solid-state NMR are given for different classes of materials, including organic compounds, oxide-based materials, glasses, alloys and intermetallic compounds.
  
  PubDate: 2012-12-16T09:05:37Z
Contributors
- Abstract: 2012
  Publication year: 2012
  Source:Annual Reports on NMR Spectroscopy, Volume 75
  
  PubDate: 2012-12-16T09:05:37Z
Chapter 4 Earth's Field Spectroscopy
- Abstract: 2012
  Publication year: 2012
  Source:Annual Reports on NMR Spectroscopy, Volume 76
  
  The Earth's magnetic field provides a convenient B 0 for performing magnetic resonance spectroscopy experiments. Providing certain environmental factors that can be overcome, the natural homogeneity of the Earth's field results in NMR signals with very narrow linewidths. In most cases, it is necessary to use a combination of a pre-polarisation scheme, and a more sensitive detection technique. SQUIDs and atomic magnetometers provide a sensitive detection scheme that is independent of the Lamour frequency. Even in the absence of peak splitting due to chemical shift, hetero- and homonuclear couplings, which are independent of field, can clearly be identified. Spin systems in the Earth's field are often strongly coupled resulting in complex spectra. As the field is then reduced, the J coupling begins to become the dominant interaction.
  
  PubDate: 2012-12-16T09:05:37Z
Subject Index
- Abstract: 2012
  Publication year: 2012
  Source:Annual Reports on NMR Spectroscopy, Volume 76
  
  PubDate: 2012-12-16T09:05:37Z
Copyright
- Abstract: 2012
  Publication year: 2012
  Source:Annual Reports on NMR Spectroscopy, Volume 75
  
  PubDate: 2012-12-16T09:05:37Z
Chapter 3 NMR Studies of Solid-State Dynamics
- Abstract: 2012
  Publication year: 2012
  Source:Annual Reports on NMR Spectroscopy, Volume 76
  
  NMR relaxometry has gained popularity in recent years, due to advances in experimental methodology and theory. We present an overview of applications of NMR relaxometry (with special focus on Field Cycling studies) to solid state, including a variety of systems ranging from simple crystals to proteins. Mechanisms and principles of the relaxation effects observed for solid state are explained. This presentation is accompanied by an outline of theoretical achievements with special attention drawn to relaxation processes in the presence of anisotropic interactions and slow dynamics. The overview is complemented by discussing the potential of NQR spectroscopy for studying dynamic processes in solids. Again, experimental examples are combined with an account of the underlying theory. Relations between NMR relaxometry, spectroscopy and diffusometry results are discussed. Different motional models, including rotational, translational and vibrational dynamics in solid state, are presented and the possibility of unambiguously determining the mechanism of motion is critically considered.
  
  PubDate: 2012-12-16T09:05:37Z
Preface
- Abstract: 2012
  Publication year: 2012
  Source:Annual Reports on NMR Spectroscopy, Volume 76
  
  PubDate: 2012-12-16T09:05:37Z
Chapter 1 Getting the Most Out of HSQC and HMBC Spectra
- Abstract: 2012
  Publication year: 2012
  Source:Annual Reports on NMR Spectroscopy, Volume 76
  
  As the title suggests, this chapter focuses on HSQC and HMBC spectra, two critically important spectra for organic structure determination by two-dimensional NMR. The relative merits of the HSQC sequence and the alternative HMQC sequence are discussed, and the performances of different versions of the HSQC sequence are evaluated, using three test compounds. It is shown that recent modifications of the HSQC sequence have eliminated or minimized earlier weaknesses of this sequence, leading to a more than twofold increase in signal/noise, particularly for edited HSQC spectra. In the case of HMBC, the impact of recent modifications of the sequence is much less than for HSQC. However, the choice of acquisition and processing parameters can have a dramatic effect on the signal/noise of HMBC spectra. A few of the numerous variants of HMBC that have been proposed to compensate for weaknesses of this sequence are considered. While they potentially yield more information, this is at the expense of signal/noise.
  
  PubDate: 2012-12-16T09:05:37Z
Chapter 2 A Review of REDCRAFT Simultaneous Investigation of Structure and Dynamics of Proteins from RDC Restraints
- Abstract: 2012
  Publication year: 2012
  Source:Annual Reports on NMR Spectroscopy, Volume 76
  
  Residual dipolar couplings (RDCs) have emerged as a viable source of NMR data for the study of protein structure and dynamics. Although very informative and accurate, their use has been limited because of challenges associated with comprehensive analyses of RDC data. The REDCRAFT software package has been designed to use RDCs exclusively for the simultaneous study of protein structure and dynamics. This has enabled the direct study of protein backbones and facilitated the fragmented study of proteins for instances where only partial data may be available. REDCRAFT's effective search engine has also resulted in a reduction in the number of RDC data required per residue to near theoretical limits. Here, we demonstrate the ability of REDCRAFT in structure determination of proteins using only backbone {N–H, Cα–Hα} RDCs from two alignment media, or {C–N, N–H, C–H} from one alignment medium and {N–H} from the second alignment medium. In addition, we present the success of REDCRAFT in identification of internal dynamics and its proper treatment in application to simulated data.
  
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Index
- Abstract: 2012
  Publication year: 2012
  Source:Annual Reports on NMR Spectroscopy, Volume 77
  
  PubDate: 2012-12-16T09:05:37Z
Copyright
- Abstract: 2012
  Publication year: 2012
  Source:Annual Reports on NMR Spectroscopy, Volume 76
  
  PubDate: 2012-12-16T09:05:37Z
Contributors
- Abstract: 2012
  Publication year: 2012
  Source:Annual Reports on NMR Spectroscopy, Volume 76
  
  PubDate: 2012-12-16T09:05:37Z
Chapter Three Steroids and NMR
- Abstract: 2012
  Publication year: 2012
  Source:Annual Reports on NMR Spectroscopy, Volume 77
  
  In this chapter, the NMR spectroscopic investigation of steroids is analyzed from five different angles, yet the general stage, the steroid-specific aspect and the provision of an illustrative example are the common themes for each perspective. Firstly, steroids and NMR are placed in their chemical, analytical and pharmaceutical context. Secondly, the characteristic challenges of steroid structure elucidation and the aspects of specific moieties of steroidal compounds are described following chronological and also stereospecific lines. Subsequently, the application of NMR methodology is reviewed with respect to host–guest chemistry, impurity profiling and isotopic labelling, such as 3H, 17O and 19F. Furthermore, the use of computer-assisted structure elucidation applied to the steroids using incremental systems, simple databases and the current sophisticated spectral prediction algorithms will be discussed and their applications compared for testosterone and tibolone. The most recently developed and also the rare, but nonetheless valuable, NMR methods will also be presented. These include covariance processing, residual dipolar couplings and high-sensitivity CC INADEQUATE experiments. Finally, suitable experiment sets for steroid structure elucidation and structure confirmation are discussed. Tibolone is used as the common thread and serves as an illustrative example throughout this chapter.
  
  PubDate: 2012-12-16T09:05:37Z
Chapter Four Structural Characterization of Zeolites by Advanced Solid State NMR Spectroscopic Methods
- Abstract: 2012
  Publication year: 2012
  Source:Annual Reports on NMR Spectroscopy, Volume 77
  
  This review overviews the application of solid state NMR spectroscopy to the structural characterization of silicate, and acidic aluminosilicate and borosilicate zeolites focusing on the utilization of new developed methods. We summarize recent results on the investigations of the distribution of silicon atoms into the zeolite framework, as well as the location of F− anions and formation of pentacoordinated silicon species in zeolites synthesized in fluoride medium. Special attention is paid here to the characterization of framework and extraframework boron and most specially aluminium species and the acid sites in zeolites. In Section 6 of this review, we present the basis and practical aspects of advanced NMR experiments used in the characterization of microporous solids paying special attention to quadrupolar nuclei and other methods based on dipolar interactions.
  
  PubDate: 2012-12-16T09:05:37Z
Chapter Two Pure Phase Encode Magnetic Resonance Imaging of Fluids in Porous Media
- Abstract: 2012
  Publication year: 2012
  Source:Annual Reports on NMR Spectroscopy, Volume 77
  
  Two classes of pure phase encoding MRI methods employed for imaging fluids in porous media, single point ramped imaging with T 1 enhancement (SPRITE) and spin echo single point imaging (SE-SPI), are reviewed. Centric scan SPRITE methods have simple signal equations and are robust in generating quantitative images with relatively short acquisition times and minimal gradient duty cycles. SE-SPI sequences are useful for measuring materials with moderate T 2 and short T 2*. T 2 mapping SE-SPI permits measuring spatially resolved T 2 distributions which provide important information about fluid occupancy of the pore space. Applications of pure phase encoding methods in porous media have been demonstrated in the measurement of static fluid content as well as in the measurement of dynamic processes.
  
  PubDate: 2012-12-16T09:05:37Z
Copyright
- Abstract: 2012
  Publication year: 2012
  Source:Annual Reports on NMR Spectroscopy, Volume 77
  
  PubDate: 2012-12-16T09:05:37Z
Contributors
- Abstract: 2012
  Publication year: 2012
  Source:Annual Reports on NMR Spectroscopy, Volume 77
  
  PubDate: 2012-12-16T09:05:37Z
Preface
- Abstract: 2012
  Publication year: 2012
  Source:Annual Reports on NMR Spectroscopy, Volume 77
  
  PubDate: 2012-12-16T09:05:37Z
Chapter One Recent Advances in Nuclear Shielding Calculations
- Abstract: 2012
  Publication year: 2012
  Source:Annual Reports on NMR Spectroscopy, Volume 77
  
  Nuclear magnetic shielding calculations have reached a great deal of sophistication, as these now incorporate both relativistic and correlation effects. Approaches now include molecular dynamics as well as effects of the medium in condensed phases. With these computational tools, calculated shielding values are now obtained under conditions as close as possible to those of a sample inside a nuclear magnetic resonance spectrometer. Indeed, computations are approaching the limits of experimental uncertainty. A brief description of new methodologies of shielding calculations is presented followed by a review of the various factors that may influence shielding. The usefulness of being able to reproduce experimental data is highlighted by citing how shielding calculations in many instances have enabled avenues for extracting information on various systems.
  
  PubDate: 2012-12-16T09:05:37Z