Paul Hodgkinson

Bio: Paul Hodgkinson is an academic researcher from Durham University. The author has contributed to research in topics: Solid-state nuclear magnetic resonance & Nuclear magnetic resonance spectroscopy. The author has an hindex of 33, co-authored 103 publications receiving 3554 citations. Previous affiliations of Paul Hodgkinson include University of Oxford & École normale supérieure de Lyon.

Chemical shift computations on a crystallographic basis: some reflections and comments

Abstract: Computations for chemical shifts of molecular organic compounds using the gauge-including projector augmented wave method and the NMR-CASTEP code are reviewed. The methods are briefly introduced, and some general aspects involving the sources of uncertainty in the results are explored. The limitations are outlined. Successful applications of the computations to problems of interpretation of NMR results are discussed and the range of areas in which useful information is obtained is illustrated by examples. The particular value of the computations for comparing shifts between resonances where the same chemical site is involved is emphasised. Such cases arise for shifts between different crystallographically independent molecules of the same chemical species, between polymorphs and for shift anisotropies and asymmetries. Copyright (c) 2007 John Wiley & Sons, Ltd.

Solid-state NMR : basic principles & practice

Abstract: Nuclear Magnetic Resonance (NMR) has proved to be a uniquely powerful and versatile tool for analyzing and characterizing chemicals and materials of all kinds. This book focuses on the latest developments and applications for "solid-state" NMR, which has found new uses from archaeology to crystallography to biomaterials and pharmaceutical science research. The book will provide materials engineers, analytical chemists, and physicists, in and out of lab, a survey of the techniques and the essential tools of solid-state NMR, together with a practical guide on applications. In this concise introduction to the growing field of solid-state nuclear magnetic resonance spectroscopy the reader will find: basic NMR concepts for solids, including guidance on the spin-1/2 nuclei concept; coverage of the quantum mechanics aspects of solid state NMR and an introduction to the concept of quadrupolar nuclei; an understanding relaxation, exchange and quantitation in NMR; an analysis and interpretation of NMR data, with examples from crystallography studies; and appendices covering spin properties of spin-1/2 nuclides as well as NMR simulation procedures.

Origins of linewidth in H1 magic-angle spinning NMR

Abstract: A detailed study of the factors determining the linewidth (and hence resolution) in 1H solid-state magic-angle spinning NMR is described. Although it has been known from the early days of magic-angle spinning (MAS) that resolution of spectra from abundant nuclear spins, such as 1H, increases approximately linearly with increasing sample rotation rate, the difficulty of describing the dynamics of extended networks of coupled spins has made it difficult to predict a priori the resolution expected for a given sample. Using recently developed, highly efficient methods of numerical simulation, together with experimental measurements on a variety of test systems, we propose a comprehensive picture of 1H resolution under MAS. The "homogeneous" component of the linewidth is shown to depend primarily on the ratio between an effective local coupling strength and the spin rate, modified by geometrical factors which loosely correspond to the "dimensionality" of the coupling network. The remaining "inhomogeneous" component of the natural linewidth is confirmed to have the same properties as in dilute-spin NMR. Variations in the NMR frequency due to chemical shift effects are shown to have minimal impact on 1H resolution. The implications of these results for solid-state NMR experiments involving 1H and other abundant-spin nuclei are discussed.

The C programming language

Abstract: This ebook is the first authorized digital version of Kernighan and Ritchie's 1988 classic, The C Programming Language (2nd Ed.). One of the best-selling programming books published in the last fifty years, "K&R" has been called everything from the "bible" to "a landmark in computer science" and it has influenced generations of programmers. Available now for all leading ebook platforms, this concise and beautifully written text is a "must-have" reference for every serious programmers digital library. As modestly described by the authors in the Preface to the First Edition, this "is not an introductory programming manual; it assumes some familiarity with basic programming concepts like variables, assignment statements, loops, and functions. Nonetheless, a novice programmer should be able to read along and pick up the language, although access to a more knowledgeable colleague will help."

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Structure of a protein determined by solid-state magic-angle-spinning NMR spectroscopy

Abstract: The determination of a representative set of protein structures is a chief aim in structural genomics Solid-state NMR may have a crucial role in structural investigations of those proteins that do not easily form crystals or are not accessible to solution NMR, such as amyloid systems1 or membrane proteins2,3,4 Here we present a protein structure determined by solid-state magic-angle-spinning (MAS) NMR Almost complete 13C and 15N resonance assignments for a micro-crystalline preparation of the α-spectrin Src-homology 3 (SH3) domain5 formed the basis for the extraction of a set of distance restraints These restraints were derived from proton-driven spin diffusion (PDSD) spectra of biosynthetically site-directed, labelled samples obtained from bacteria grown using [1,3-13C]glycerol or [2-13C]glycerol as carbon sources This allowed the observation of long-range distance correlations up to ∼7 A The calculated global fold of the α-spectrin SH3 domain is based on 286 inter-residue 13C–13C and six 15N–15N restraints, all self-consistently obtained by solid-state MAS NMR This MAS NMR procedure should be widely applicable to small membrane proteins that can be expressed in bacteria

Absolute comparison of simulated and experimental protein-folding dynamics

Abstract: Protein folding is difficult to simulate with classical molecular dynamics Secondary structure motifs such as α-helices and β-hairpins can form in 01–10 µs (ref 1), whereas small proteins have been shown to fold completely in tens of microseconds2 The longest folding simulation to date is a single 1-µs simulation of the villin headpiece3; however, such single runs may miss many features of the folding process as it is a heterogeneous reaction involving an ensemble of transition states4,5 Here, we have used a distributed computing implementation to produce tens of thousands of 5–20-ns trajectories (700 µs) to simulate mutants of the designed mini-protein BBA5 The fast relaxation dynamics these predict were compared with the results of laser temperature-jump experiments Our computational predictions are in excellent agreement with the experimentally determined mean folding times and equilibrium constants The rapid folding of BBA5 is due to the swift formation of secondary structure The convergence of experimentally and computationally accessible timescales will allow the comparison of absolute quantities characterizing in vitro and in silico (computed) protein folding6