High-resolution NMR studies of solid halogenated organic compounds

This thesis is a study of solid halogenated organic compounds by Nuclear Magnetic Resonance Spectroscopy (NMR) in an attempt to extract previously inaccessible information. The first part of the thesis is concerned with three fluorinated steroids, studied by observing (^1)H, (^13)C and (^19)F nuclei. A number of experimental techniques are employed to verify solution-state and solid-state spectral assignments, and spectral anomalies are discussed. Both proton-coupled and proton-decoupled (^19)F solid-state spectra, recorded using specially designed spectrometer hardware, are presented. The huge gain in resolution afforded by the implementation of proton decoupling allows static and MAS spectra to yield previously inaccessible information pertaining to various NMR parameters of the fluorine nuclei. Advantages of (^1)H→(^19)F cross-polarisation experiments over single-pulse experiments are explained and rotational resonance, dipolar dephasing, T(_1), measurement and spin-exchange experiments are presented from which information regarding phenomena such as spin diffusion and polymorphism is gleaned. The second part of the thesis focusses on the topic of residual dipolar coupling, the transfer of quadrupolar effects to spin-1/2 nuclei via dipolar coupling and/or anisotropy m indhect coupling. Unexpected, field-dependent, multiplicities for signals in spectra of spin-1/2 nuclei are observed, which can be used to evaluate certain fundamental NMR parameters including the quadrupolar coupling constant and, m favourable cases, anisotropy in indirect coupling. The phenomenon is comprehensively studied for the (^13)C, (^35,37)Cl and (^13)C, (^79,81)Br spin-pairs in a range of solid halogenated compounds. Coupling to more than one halogen nucleus and long- range (non-bonded) coupling are considered. First-order perturbation, inverse first- order and "exact" theories, that allow the multiplet line positions to be predicted, are introduced and their results are subsequently compared to the experimentally observed the positions. Rapid molecular motion is shown to negate the effects of residual dipolar coupling and the phenomenon is analysed with the aid of NQR measurements

A guide to the identification of metabolites in NMR-based metabonomics/metabolomics experiments

Metabonomics/metabolomics is an important science for the understanding of biological systems and the prediction of their behaviour, through the profiling of metabolites. Two technologies are routinely used in order to analyse metabolite profiles in biological fluids: nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS), the latter typically with hyphenation to a chromatography system such as liquid chromatography (LC), in a configuration known as LC–MS. With both NMR and MS-based detection technologies, the identification of the metabolites in the biological sample remains a significant obstacle and bottleneck. This article provides guidance on methods for metabolite identification in biological fluids using NMR spectroscopy, and is illustrated with examples from recent studies on mice

Aerospace medicine and biology: A continuing bibliography with indexes (supplement 360)

This bibliography lists 217 reports, articles and other documents introduced into the NASA Scientific and Technical Information System during February 1992. Subject coverage includes: aerospace medicine and physiology, life support systems and man/system technology, protective clothing, exobiology and extraterrestrial life, planetary biology, and flight crew behavior and performance

Comprehensive T-matrix Reference Database: A 2009-2011 Update

The T-matrix method is one of the most versatile and efficient theoretical techniques widely used for the computation of electromagnetic scattering by single and composite particles, discrete random media, and particles in the vicinity of an interface separating two half-spaces with different refractive indices. This paper presents an update to the comprehensive database of peer-reviewed T-matrix publications compiled by us previously and includes the publications that appeared since 2009. It also lists several earlier publications not included in the original database

Structure and Dynamics of Coil-like Molecules by Residual Dipolar Couplings

Nuclear magnetic resonance (NMR) spectroscopy provides us with many means to study biological macromolecules in solution. Proteins in particular are the most intriguing targets for NMR studies. Protein functions are usually ascribed to specific three-dimensional structures but more recently tails, long loops and non-structural polypeptides have also been shown to be biologically active. Examples include prions, -synuclein, amylin and the NEF HIV-protein. However, conformational preferences in coil-like molecules are difficult to study by traditional methods. Residual dipolar couplings (RDCs) have opened up new opportunities; however their analysis is not trivial. Here we show how to interpret RDCs from these weakly structured molecules. The most notable residual dipolar couplings arise from steric obstruction effects. In dilute liquid crystalline media as well as in anisotropic gels polypeptides encounter nematogens. The shape of a polypeptide conformation limits the encounter with the nematogen. The most elongated conformations may come closest whereas the most compact remain furthest away. As a result there is slightly more room in the solution for the extended than for the compact conformations. This conformation-dependent concentration effect leads to a bias in the measured data. The measured values are not arithmetic averages but essentially weighted averages over conformations. The overall effect can be calculated for random flight chains and simulated for more realistic molecular models. Earlier there was an implicit thought that weakly structured or non-structural molecules would not yield to any observable residual dipolar couplings. However, in the pioneering study by Shortle and Ackerman RDCs were clearly observed. We repeated the study for urea-denatured protein at high temperature and also observed indisputably RDCs. This was very convincing to us but we could not possibly accept the proposed reason for the non-zero RDCs, namely that there would be some residual structure left in the protein that to our understanding was fully denatured. We proceeded to gain understanding via simulations and elementary experiments. In measurements we used simple homopolymers with only two labelled residues and we simulated the data to learn more about the origin of RDCs. We realized that RDCs depend on the position of the residue as well as on the length of the polypeptide. Investigations resulted in a theoretical model for RDCs from coil-like molecules. Later we extended the studies by molecular dynamics. Somewhat surprisingly the effects are small for non-structured molecules whereas the bias may be large for a small compact protein. All in all the work gave clear and unambiguous results on how to interpret RDCs as structural and dynamic parameters of weakly structured proteins.Ydinmagnettinen resonanssi spektroskopia (NMR) tarjoaa mahdollisuuden tutkia biologisia molekyylejä lioksessa. Varsinkin proteiinit ovat oleet tutkimusten kohteina. Proteiinien on perinteisesti ajateltu olevan aktiivisia vain laskostuneessa, kolmiuloittesessa muodossaan. Viimeaikoina on kuitenkin saatu yhä enemmän tietoa myös rakenteettomien tai heikosti rakenteellisten osien tärkeydestä proteiinien toiminnassa. Näiden osien tutkiminen perinteisin menetelmin on kuitenkin osoittautunu vaikeaksi. Jäännösdipolikytkentä (RDC) on tuonut uusia mahdollisuuksia tutkimuksiin. Jäännösdipolikytkentä tulee haivattavaksi kun käytetään ympäristöä, missä molekyyli törmäilee liuoksessa olevan esteen kanssa ja näin yleensä nollaan keskiarvoistuva kytkentä on havaittavissa. Molekyylin muodosta riippuu miten lähelle sen keskipiste pääsee tätä estettä tai seinämää. Tästä syystä johtuva virhe tulee ottaa huomioon tulosten tarkastelussa. Aikaisemmin luultiin, että laskostumattomista tai heikosti laskostuneista molekyyleistä ei voida mitata jäännösdipolikytkentöjä. Kuitenkin Shortle ja Ackerman ovat töissään osoittaneet, että tämä on mahdollista. Jatkoimme tutkimuksia käyttäen mallina homoplymeerejä ja jatkoimme molekyyli dynamiikkaan. Työmme tuloksena syntyi selvä kuva miten laskostumattomia molekyylejä tulisi mitata jäännösdipolikytkentöjen avulla

NASA thesaurus. Volume 1: Hierarchical Listing

There are over 17,000 postable terms and nearly 4,000 nonpostable terms approved for use in the NASA scientific and technical information system in the Hierarchical Listing of the NASA Thesaurus. The generic structure is presented for many terms. The broader term and narrower term relationships are shown in an indented fashion that illustrates the generic structure better than the more widely used BT and NT listings. Related terms are generously applied, thus enhancing the usefulness of the Hierarchical Listing. Greater access to the Hierarchical Listing may be achieved with the collateral use of Volume 2 - Access Vocabulary and Volume 3 - Definitions