Dissertations / Theses on the topic 'NMR methods'
To see the other types of publications on this topic, follow the link: NMR methods.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'NMR methods.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Edden, Richard Anthony Edward. "New methods in NMR spectroscopy." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613719.
Full text
2
McLachlan, Andrew S. "Improved NMR methods for impurity analysis." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.503032.
Full textAbstract:
The results presented in this thesis are concerned with improvements to liquid-state Nuclear Magnetic Resonance (NMR) spectroscopic techniques and their application to small molecule (i.e. with molecular weight < 500) mixture systems, with the aim of separating signals from individual components. The results presented in this thesis provide an insight into NMR mixture analysis, which may ultimately have applications in the field of drug discovery and development.
3
Hernandez, Cid Aaron. "New NMR methods for mixture analysis." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/new-nmr-methods-for-mixture-analysis(8ee7b062-e1cf-4c31-9a4b-3e6603b2d29c).html.
Full textAbstract:
This thesis is focussed on the investigation of matrices for matrix-assisted diffusion-ordered spectroscopy (MAD). Diffusion-ordered spectroscopy (DOSY) is a family of experiments where the resonances in the chemical shift dimension are further dispersed in an extra dimension according to diffusion coefficient. A typical DOSY spectrum shows one single diffusion coefficient for all the resonances coming from one single species. However, If two or more resonances overlap, the diffusion resolution of the DOSY spectrum is compromised and a spurious diffusion coefficient results, intermediate between the species. In case of signal overlap, the use of more advanced processing methods aids to separate two analytes that differ by at least 30% in diffusion coefficient. In practice, many mixtures contain species of similar diffusion coefficients whose resonances overlap in the chemical shift dimension. The addition of co-solutes can modify the chemical environment (matrix), with which different analytes interact to different extents, and enhance the diffusion resolution of DOSY. However, the addition of co-solutes can risk the benefits of DOSY by increasing the probability of signal overlap. Signal overlap in MAD is avoided by using a 1H NMR-invisible surfactant such as sodium perfluorooctanoate (NaPFO), which has replaced each proton by a fluorine atom. PFO micelles are a tunable matrix which allows the separation of analytes via coulombic interactions by adjusting the pH. Differences in diffusion coefficient in NaPFO solution can be analysed using a modified Lindman's law to model the diffusion coefficient as a function of pH. The model rationalises the binding constants of analytes to PFO micelles with good accuracy, subject to the spectral data quality. Another alternative to resolve diffusion coefficients using the invisible MAD approach is by means of a commercially available alkyl surfactant like cetyltrimethylammonium bromide (CTAB). CTAB in high ionic strength solution forms worm-like micelles whose resonances can be filtered out from the final DOSY spectrum. CTAB worm-like micelles have short transverse relaxation times compared to all of the analytes in the mixture. If a transverse relaxation filter is positioned at the beginning of a standard DOSY pulse sequence, as in PROJECT-Oneshot, the strong CTAB signals vanish and leave behind only the analyte resonances and hence avoid signal overlap. Finally, the use of bovine serum albumin (BSA) as a potential invisible matrix, using a similar approach to CTAB worm-like micelles is investigated, using a relaxation-weighted DOSY pulse sequence to suppress most of the BSA background signal (at a cost in analyte signal to noise ratio). An alternative to suppress most of the BSA background and preserve most of the analyte signal is by means of mild transverse relaxation filtration and spectral editing to obtain an edited DOSY spectrum that shows only the analyte signals. Nonetheless, it is a shame that useful MAD results can only be obtained under a narrow set of conditions: i) different mole ratios BSA: analyte to aid diffusion resolution, ii) mild T2 filtration to improve analyte signal to noise ratio and iii) spectral editing to remove residual BSA background.
4
Hallberg, Fredrik, Erik Pettersson, Sergey Dvinskikh, Thomas Vernersson, Göran Lindberg, István Furó, and Peter Stilbs. "Electrophoretic NMR (eNMR) – methods and applications." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-193097.
Full text
5
Hallberg, Fredrik, Erik Pettersson, Sergey Dvinskikh, Thomas Vernersson, Göran Lindberg, István Furó, and Peter Stilbs. "Electrophoretic NMR (eNMR) – methods and applications." Diffusion fundamentals 7 (2007) 13, S. 1-2, 2007. https://ul.qucosa.de/id/qucosa%3A14170.
Full text
6
Bennett, David Alexander. "Structural methods in solid-state NMR." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13242/.
Full textAbstract:
New solid-state NMR experiments for measuring internuclear distances are designed using symmetry principles. The “recoupling” sequences described here are intended to reintroduce the MAS-averaged heteronuclear dipole-dipole coupling between a spin-1/2 nucleus (e.g. 1H) and a half-integer quadrupolar nucleus (e.g. 17O, I = 5/2). The magnitude of the dipolar interaction depends on the separation between the coupled nuclei, so the evolution of the spin system under the recoupled Hamiltonian can be used to measure the internuclear distance. Simulations of the spin dynamics are used initially to select candidate sequences and these are subsequently employed to measure both long-range and direct O–H distances in powdered L-Tyrosine.HCl (isotopically enriched with 17O at 20%to 30% at the O$^\eta$ site). Improvements to existing methods for the data analysis for this type of NMR experiment are also discussed, including the restriction and/or removal of certain fit parameters and the explicit inclusion of inhomogeneous radio-frequency fields as part of the fitting procedure. The effects of processing on the uncertainty of experimentally determined distances are considered, and a new analysis method which circumvents several of these effects is presented. Similar recoupling sequences can be used to measure the anisotropy of proton chemical shifts, and some preliminary results are also presented for this application. A systematic method for the assignment of congested spin-1/2 spectra resulting from molecules with large numbers of chemically similar sites is also described. This makes use of a comparison between the chemical shift tensor measured as usual by the 2D-PASS experiment and its principal components calculated from first principles using the density functional theory package CASTEP. The initial peak assignment is generated randomly and then varied using a steepest-ascent hill climbing algorithm with the square sum of the difference between the experimental and calculated principal values of the chemical shift tensor as the target function. The new method is tested on the 13C spectrum of the anti-inflammatory drug flufenamic acid and found to be superior to simple assignments using only the isotropic chemical shift.
7
Swan, Iain. "Advanced NMR methods for formulation analysis." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/advanced-nmr-methods-for-formulation-analysis(42a72ebf-b797-403f-a3bc-353e0e3987eb).html.
Full textAbstract:
This thesis concentrates on diffusion-ordered spectroscopy (DOSY): a technique in liquid state nuclear magnetic resonance (NMR) spectroscopy that is able to distinguish different chemical species by their size in solution, and measure species’ diffusion coefficients. DOSY is an invaluable tool to analyse and resolve the signals of mixtures of chemicals in solution. DOSY measures an ensemble of nuclei in a mixture, using pulsed field gradients (PFGs) to encode, and later decode, the positions of spins. This provides information on the root mean square distance that spins diffuse during a delay between a pair of PFGs, which allows the determination of diffusion coefficients. However, DOSY is susceptible to a number of complications. Where a sample convects, the distance molecules move during the delay is greater than for simple diffusion, and the estimate of the diffusion coefficient becomes greater than the true value. Rayleigh-Bénard convection has been known in NMR for a long time, and is known to result from heating the base of an NMR sample, giving rise to negative vertical temperature gradients. Here, cooling the base (and inadvertently the sides) of the sample is also shown to cause convection from transverse temperature gradients, known as Hadley convection and commonly observed in atmospheric circulation. The theory for convection from transverse temperature gradients is given and recommendations to reduce convection in NMR are made. DOSY analysis can also be challenging where signals from different species overlap. In such instances, it can help to reduce the overlap, which can be achieved by collapsing multiplets into singlet signals: pure shift NMR is a technique that uses band-selection in order to refocus scalar coupling during the free induction decay, leaving pure chemical shift information. However, PFGs can vary in strength across the sample, which can have an effect on band selective experiments, such as Zangger-Sterk pure shift experiments, in the measured peak amplitudes, and where DOSY is combined with the Zangger-Sterk pure shift sequence, the apparent diffusion coefficients are also altered, seemingly as a function of chemical shift. A correction for this is given, simply using a DOSY and a DOSY pure shift experiment, as an alternative to the current literature method (gradient mapping).An investigation into an emulsion, agrochemically important for the delivery of active ingredients (fertiliser,pesticides, etc.) to plants, was then undertaken, in the hopes of finding restricted diffusion, but instead discovering substantial chemical exchange on the diffusional timescale. Finally a program was written for the automated acquisition of DOSY data, without the need for a human controller to calibrate DOSY parameters for the optimum acquisition.
8
Saalwächter, Kay. "Heteronuclear recoupling methods in solid state NMR." [S.l. : s.n.], 2000. http://ArchiMeD.uni-mainz.de/pub/2000/0070/diss.pdf.
Full text
9
Ginzinger, Simon Wolfgang. "Bioinformatics Methods for NMR Chemical Shift Data." Diss., lmu, 2008. http://nbn-resolving.de/urn:nbn:de:bvb:19-80776.
Full text
10
Hollingsworth, K. G. "Characterisation of emulsion systems using NMR methods." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604170.
Full textAbstract:
Several aspects of emulsion characterisation via NMR are explored. This thesis begins by considering previous experimental work in determining the droplet-size distributions of emulsion systems by magnetic resonance restricted self-diffusion measurements. This is developed by applying regularisation techniques to analyse restricted diffusion measurements and avoid the limitation of fitting a particular functional form for the droplet-size distribution. Droplet-sizing is then extended to flowing emulsions by means of flow-compensated diffusion measurement. The success of this strategy is evaluated for several different model oil-in-water emulsions. An inverse Abel transform technique is applied to produce spatially-resolved droplet-size distributions for both stationary and flowing emulsion systems flowing within a pipe: a significant time saving is achieved by exploiting the symmetry of the system. The flow patterns of emulsions through an orifice plate, an elementary type of static mixer, are then considered. The ability of magnetic resonance to produce spatially-resolved velocity maps is exploited to make rheological measurement of emulsion systems. For the first time, the effect of altering the droplet-phase volume concentration on rheology is considered using magnetic resonance methods and the analysis is extended to emulsions having an apparent yield stress. The phenomenon of shear-induced migration of emulsions, unlike that of solid suspensions, has not previously been well studied: this work presents the first study of this effect by magnetic resonance methods. The effect of changing the volume concentration of droplets, the surfactant and the rotation speed of a Couette geometry are elucidated. One of the principal drawbacks of determining emulsion droplet-size distributions by magnetic resonance diffusion measurements is the time-consuming nature of the measurements: this work thus presents a fast method of making these measurements. This method is exploited to study both emulsion droplet coalescence and emulsion droplet breakup in a simple stirred vessel.
11
Giesecke, Marianne. "Characterizing ions in solution by NMR methods." Doctoral thesis, KTH, Tillämpad fysikalisk kemi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-149552.
Full textAbstract:
NMR experiments performed under the effect of electric fields, either continuous or pulsed, can provide quantitative parameters related to ion association and ion transport in solution. Electrophoretic NMR (eNMR) is based on a diffusion pulse-sequence with electric fields applied in the form of pulses. Magnetic field gradients enable the measurement of the electrophoretic mobility of charged species, a parameter that can be related to ionic association. The effective charge of the tetramethylammonium cation ion in water, dimethylsulphoxide (DMSO), acetonitrile, methanol and ethanol was estimated by eNMR and diffusion measurements and compared to the value predicted by the Debye-Hückel-Onsager limiting law. The difference between the predicted and measured effective charge was attributed to ion pairing which was found to be especially significant in ethanol. The association of a large set of cations to polyethylene oxide (PEO) in methanol, through the ion-dipole interaction, was quantified by eNMR. The trends found were in good agreement with the scarce data from other methods. Significant association was found for cations that have a surface charge density below a critical value. For short PEO chains, the charge per monomer was found to be significantly higher than for longer PEO chains when binding to the same cations. This was attributed to the high entropy cost required to rearrange a long chain in order to optimize the ion-dipole interactions with the cations. Moreover, it was suggested that short PEO chains may exhibit distinct binding modes in the presence of different cations, as supported by diffusion measurements, relaxation measurements and chemical shift data. The protonation state of a uranium (VI)-adenosine monophosphate (AMP) complex in aqueous solution was measured by eNMR in the alkaline pH range. The question whether or not specific oxygens in the ligand were protonated was resolved by considering the possible association of other species present in the solution to the complex. The methodology of eNMR was developed through the introduction of a new pulse-sequence which suppresses artifactual flow effects in highly conductive samples. In another experimental setup, using NMR imaging, a constant current was applied to a lithium ion (Li ion) battery model. Here, 7Li spin-echo imaging was used to probe the spin density in the electrolyte and thus visualize the development of Li+ concentration gradients. The Li+ transport number and salt diffusivity were obtained within an electrochemical transport model. The parameters obtained were in good agreement with data for similar electrolytes. The use of an alternative imaging method based on CTI (Constant Time Imaging) was explored and implemented.QC 20140825
12
Moorcroft, D. "Molecular structure studies using NMR relaxation methods." Thesis, University of Salford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.353972.
Full text
13
Maguire, Mahon Lawrence. "Computational methods for NMR studies of proteins." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614946.
Full text
14
Moutzouri, Pinelopi. "New and improved methods for mixture analysis by NMR." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/new-and-improved-methods-for-mixture-analysis-by-nmr(d6bad99a-36dd-440b-a7b1-f8243a8ab4a3).html.
Full textAbstract:
A unique characteristic of NMR is that, unlike other spectroscopic techniques, it separates the excitation of signals from their detection. By manipulating the type of signal excitation used, the chemical information content of a spectrum can be controlled. This versatility has made NMR a powerful and flexible weapon in the analytical arsenal of chemists, not only for the determination of structural, chemical, dynamic, and physical properties of molecules, but also for the analysis of mixtures, since NMR has the ability to study these intact without the need for physical separation. Chapter 1 contains an introduction to the theoretical NMR background necessary for this thesis. Chapter 2, 3 and 6 detail the development of new methods that suppress 13C satellites not only in conventional 1D 1H and 19F spectra, but also in 1H DOSY spectra, and can facilitate the analysis of minor components in high dynamic range mixtures (i.e. those with a wide range of concentrations). Chapter 4 introduces a new experiment which suppresses low-level artefacts in pure shift NMR, and gives clean pure shift spectra that can be used for the detection of minor components in the presence of strong signals. Chapter 5 and 7 illustrate how 19F NMR can be exploited for the acquisition of simplified proton spectra associated with a given 19F chemical shift, or for the virtual separation of mixture components using broadband 19F DOSY. Chapter 8 summarises the conclusions extracted from the research introduced in the main body of this thesis, and gives suggestions for future developments. Chapters 2, 3, 4, 5, and 7 contain published research articles and their Supporting Information and are presented without modification. Chapter 6 is presented as a manuscript intended for publication.
15
Wiesmath, Anette. "NMR methods for strongly inhomogeneous magnetic fields: application on elastomers using the NMR-mouse." [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=96487721X.
Full text
16
Luchette, Paul A. "Novel methods for investigating membrane proteins by NMR." [Kent, Ohio] : Kent State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=kent1146509524.
Full textAbstract:
Thesis (Ph.D.)--Kent State University, 2006.Title from PDF t.p. (viewed Sept. 19, 2006). Advisor: R. S. Prosser. Keywords: membrane, NMR, protein, lovemonkey, lyotropic, liquid crystal, bicelle. Includes bibliographical references (p. 250-256).
17
Ball, Thomas James. "Development of new methods in solid-state NMR." Thesis, University of Glasgow, 2008. http://theses.gla.ac.uk/385/.
Full textAbstract:
Many chemically important nuclei are quadrupolar with half-integer spin (i.e., spin I = 1.5, 2.5, etc.) The presence of quadrupolar broadening for such nuclei can limit the information that may be extracted using NMR. MAS is able to remove first-order quadrupolar broadening but can only reduce the second-order contribution to the linewidth. The MQMAS and STMAS techniques have enabled high-resolution NMR spectra of half-integer quadrupolar nuclei in the solid state to be obtained by two-dimensional correlation under MAS conditions. Both of these experiments have several well-known limitations. One is that the conversion pulses in particular are very inefficient and the other is that the longer acquisition times required for two-dimensional experiments can be a limiting factor. Both of these disadvantages are addressed in this thesis. For the former case, existing composite pulse schemes designed to improve the efficiency of the conversion of multiple-quantum coherences are compared using 27Al and 87Rb MQMAS NMR of a series of crystalline and amorphous materials. In the latter case, a new experiment, named STARTMAS, is introduced that enables isotropic spectra of spin I = 1.5 spectra to be acquired in real time. The theoretical basis of the technique is explained and its applicability demonstrated using 23Na and 87Rb NMR of a wide range of solids. The nuclear Overhauser effect (NOE) is one of the most widely exploited phenomena in NMR and is now widely used for molecular structure determination in solution. NOEs in the solid state are rare and those to quadrupolar nuclei rarer still, this being due to the general absence of motion on the correct timescale and the usual efficiency of quadrupolar T1 relaxation, respectively. In this thesis, 11B{1H} transient NOE results are presented for a range of solid borane adducts. A comparison is made of the 11B NMR enhancements observed under MAS and static conditions and a rationale is proposed for the behaviour in the latter case.
18
Pages, Guilhem, and Philip W. Kuchel. "NMR methods for the fast recording of diffusion." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-193190.
Full textAbstract:
The time taken to complete an NMR diffusion experiment is typically ~10 minutes. For systems that rapidly evolve conventional pulsed field gradient spin-echo (PGSE) experiments cannot be used to obtain reliable estimates of molecular mobility. Modern ‘fast-diffusion’ experiments provide a means of obtaining this information and thus open up new vistas for the application of PGSE NMR. In this paper we review the various advantages and disadvantages of these methods.
19
Kurkiewicz, Teresa. "New NMR methods for studying dynamics in solids." Thesis, University of Glasgow, 2011. http://theses.gla.ac.uk/2613/.
Full textAbstract:
There is currently much interest in the investigation of dynamics in solids and the primary goal of this thesis is to present well-known and new NMR methods used for studying motion on Larmor and spectral timescale. The quadrupolar interaction usually dominates solid-state NMR spectra of quadrupolar nuclei. When the magnitude of quadrupolar interaction is large then the second-order correction to the dominant Zeeman Hamiltonian must be considered. Owing to this second-order quadrupolar effect, NMR peaks can be displaced from their chemical shift positions by a second-order shift. When considering motional averaging of the second-order shift, the critical frequency is the Larmor frequency, 0. In the case of motion that is faster than the Larmor precession, the isotropic quadrupolar shift is affected. This analogous phenomenon in solution-state NMR is known as the "dynamic shift". In Chapter 4, it will be shown that multiple-quantum NMR measurements of isotropic second-order quadrupolar shifts are a simple way to probe nanosecond timescale motions in solids. An analysis of one- and two-dimensional 11B MAS NMR spectra of three isomers of the closo-carboranes gives the results that provide the first evidence for the presence of solid-state dynamic shifts. There are several experiments that provide a sensitive test for the presence of dynamics on spectral timescale. One piece of evidence for dynamics on the spectral timescale is a motional broadening of quadrupolar satellite-transition spinning sidebands. Therefore, it is possible to investigate the influence of dynamic reorientation on satellite-transitions MAS spectra by recording variable-temperature one-dimensional spectra with wide spectral width or by comparing two-dimensional STMAS spectra with MQMAS spectra. These methods can be extended to 2H NMR spectroscopy as the sidebands observed in the magic angle spinning (MAS) NMR spectrum of a spin I = 1 2H nucleus may be very strongly broadened due to interference between the line-narrowing effects of MAS and the dynamics-driven reorientation of the 2H quadrupole tensor, if motion is present in the solid. In the last chapter, the 27Al, 31P and 2H NMR study of AlPO-34 type materials with the topology of chabazite are undertaken and the use of the full range of NMR methods to develop a structure and dynamic behaviour of these materials is presented. In addition, the NMR calculations are performed in order to combine DFT calculations with experimental data. Finally, GaPO-34 samples were investigated to extract information about the effects of Ga substitution in AlPO-34 on dynamical behaviour.
20
Tatolo, Godiraone. "Improved NMR-based methods for molecular structure elucidation." Thesis, University of Bristol, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680109.
Full textAbstract:
The use of 1H_I3C NMR correlations and its corresponding I1JCH has found a tremendous use in structural elucidation of organic compounds. Chapter 1 highlights different methods for determination of IH_13C correlations and for the measurement of I1JCH. In this work we reported two improved methods for determination of IH_I3C correlations (CTgc2HMBC) and, for the measurement of nJCH (SelEXSIDE). Chapter 2 describes the work undeliaken in order to quantify improvements to the gradient heteronuclear multiple bond correlation (HMBC) experiment specifically to design a constant time gradient HMBC (CTgc2HMBC) with adiabatic pulses. This was done in order to remove IH_IH modulation during fl , which causes cross-peak broadening, to simultaneously maximise sensitivity and resolution and then compare their performance against comparable non-constant time experiments. CTgc2HMBC experiment has shown slightly narrower cross peaks in the FI dimension which is maximised at high FI resolution especially 20 Hz/pt, compared to analogous gc2HMBC which is limited by IH-IH modulation. The CTgc2HMBC has been shown to be more efficient for weak IH_ 13C correlations. Chapter 3 describes the improvement made to the slow, easy to use EXSIDE sequence. The EXSIDE sequence was made to be doubly-selective in both the FI (I3C) and F2 (IH) domains. The modification, named Sel-EXSIDE reduces the number of tl datapoints used by reducing the FI spectrum width substantially, and thus reducing a multi-hour (7 hours 30 minutes 0 f experiment time to 0 btain 3 -7 co up ling co nstants) experiment to a matter of minutes (less than 10 minutes to obtain one coupling constant) while still allowing nJCH coupling constants to be resolved to -I Hz/pt resolution. The SelEXSIDE pulse sequence has been shown to work for determination of all measurable nJCH for both small (2-ethylI- indanone) and large (strychnine) organic molecules. Coupling constants obtained using SelEXSIDE, gave low mean errors and standard deviations when compared to other methods like Line-fitting procedures and calculated values using DFT.
21
Haies, Ibraheem. "New methods for nitrogen-14 solid state NMR." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/382902/.
Full textAbstract:
Nitrogen is one of the most abundant elements. It plays a significant role in different scientific disciplines, like materials science, chemistry, biochemistry and pharmaceutical chemistry. Most NMR studies of nitrogen have been performed on samples enriched with 15N. To avoid enrichment and overcome the problem of using NMR where isotopic enrichment is not feasible, NMR of 14N that has 99.6% natural abundance is a viable alternative. However, the 14N spin quantum number 1 and high quadrupolar interactions lead to a few challenges for NMR investigation. Recently, two approaches appeared which overcome the complications associated to the first order quadrupolar line broadening, namely indirect detection using vicinal nuclei and overtone transition. Paper 1 describes a novel version of HMQC experiments, which requires the application of a moderate RF field to the 14N nucleus to correlate the 14N with a 13C ‘spy’ nucleus, which provides good sensitivity on natural abundance and labelled materials. In addition, overtone 14N NMR spectroscopy is a promising route for the direct detection of 14N signals with good spectral resolution. Overtone NMR is the main topic of my research. To overcome the poor efficiency of the overtone transition, polarization transfer techniques have been implemented. Papers 2 and 4 present respectively polarization transfer methods from 1H to the 14N overtone using symmetry-based R-sequences and cross polarization methods. Signal enhancements of 6.7 and 2 have been obtained when cross polarization methods and symmetry-based R-sequences are used respectively. Paper 3 shows results obtained with the DOR (double rotation) technique to reduce 14N overtone linewidth, with 14N overtone spectra with linewidth reduced by nearly one order of magnitude. Analysis of the results has been facilitated through the use of a new simulation strategy for 14N overtone NMR spectroscopy of spinning samples, using Spinach library.
22
Pages, Guilhem, and Philip W. Kuchel. "NMR methods for the fast recording of diffusion." Diffusion fundamentals 6 (2007) 3, S. 1-17, 2007. https://ul.qucosa.de/id/qucosa%3A14177.
Full textAbstract:
The time taken to complete an NMR diffusion experiment is typically ~10 minutes. For systems that rapidly evolve conventional pulsed field gradient spin-echo (PGSE) experiments cannot be used to obtain reliable estimates of molecular mobility. Modern ‘fast-diffusion’ experiments provide a means of obtaining this information and thus open up new vistas for the application of PGSE NMR. In this paper we review the various advantages and disadvantages of these methods.
23
Azhar, Mueed [Verfasser], and Jan G. [Akademischer Betreuer] Korvink. "Simulation of NMR experiments using particle simulation methods." Freiburg : Universität, 2018. http://d-nb.info/1155722485/34.
Full text
24
Javed, M. A. (Muhammad Asadullah). "Advanced liquid and gas NMR methods for probing topical materials." Doctoral thesis, Oulun yliopisto, 2019. http://urn.fi/urn:isbn:9789526222493.
Full textAbstract:
Abstract The present thesis exploits advanced liquid and gas NMR methods for the characterization of various interesting materials. The methods used to study the structural properties of thermally modified wood, ionic liquids, cements, shales, and porous organic cages include MRI, NMR cryoporometry, Laplace NMR, multidimensional Laplace NMR, as well as ¹²⁹Xe and ¹⁹F NMR. The commonality factor in all the studies is the usage of either inherent or introduced liquid or gas molecules to probe the topical materials. The MRI method was utilized to visualize the water absorption phenomena in the thermally modified pine wood. High-resolution images made it possible to observe the spatial distribution of free water and the changes in the rate of absorption of water in wood samples modified at different temperatures. The images also helped to resolve the individual resin channels. T₂ maps enabled us to observe the changes in the relaxation values of free water in thermally modified wood as compared to their unmodified reference wood samples. The multidimensional Laplace NMR methods were exploited to study the structural and dynamical properties of a novel halogen-free, boron-based ionic liquid (hf-BIL). NMR self-diffusion (D) experiments showed the presence of two coexisting dynamic phases in hf-BIL. Multidimensional D − T₂ correlation experiments made it possible to determine the T₂ relaxation times of the slow and fast diffusing phases. T₂ − T₂ relaxation exchange measurements allowed quantifying the exchange rates of anions and cations between the phases. Moreover, the theoretical modeling of the experimental data revealed that the slow diffusing phase was composed of anion-cation aggregates, while the fast diffusing phase was comprised of free anions and cations. ¹²⁹Xe NMR analysis of the xenon adsorbed in the cements and shales helped us to determine their porous structures. The method exploits the high sensitivity of the chemical shift of ¹²⁹Xe to its local environment. The chemical shift value of ¹²⁹Xe enabled us to estimate the size of the mesopores in the cement samples. The exchange spectroscopy (EXSY) measurements were used to determine the exchange rates between the free gas and mesopores of the cement samples. ¹²⁹Xe NMR spectra of the shale samples provided information about pore sizes and paramagnetic compounds. ¹H NMR cryoporometry measurements of the shale samples immersed in acetonitrile made it possible to analyze the pore size distribution ranging from 10 to over 100 nm. Moreover, T₂ − T₂ exchange measurements helped us to quantify the exchange rates of acetonitrile in the shale samples. Xenon and SF₆ were used as internal reporters to gain versatile information on adsorption phenomena in the cage and window cavities of the crystalline porous organic cages. ¹²⁹Xe NMR analysis of the adsorbed xenon helped us to determine the diffusion coefficients and activation energy of diffusion as well as thermodynamic parameters. With the help of T₂ relaxation time values, it was possible to estimate the exchange rates between cage and window cavities. Chemical exchange saturation transfer (CEST) experiments resolved a window cavity site, which arises from crystal defects in porous organic cages. In addition, ¹⁹F NMR analysis made it possible to estimate the relaxation rates and diffusion coefficients of SF₆ gas in porous organic cages. Modelling of the T₁, T₂ and diffusion data confirmed that the cage to window exchange is the completely dominating mechanism for ¹²⁹Xe T₂ relaxation. T₁ relaxation is dominated by diffusion modulated dipole-dipole relaxation (DDinter) and chemical shift anisotropy (CSA) relaxation due to local cavity mobility. Whereas, in case of SF₆ T₂ data, the dominating mechanism is diffusion modulated dipole-dipole relaxation and for T₁ the local tumbling of SF₆ in cage cavity is the key dynamics behind the dipole-dipole and CSA mechanismsOriginal papers The original publications are not included in the electronic version of the dissertation. Javed, M. A., Kekkonen, P. M., Ahola, S., & Telkki, V.-V. (2015). Magnetic resonance imaging study of water absorption in thermally modified pine wood. Holzforschung, 69(7), 899–907. https://doi.org/10.1515/hf-2014-0183 Javed, M. A., Ahola, S., Håkansson, P., Mankinen, O., Aslam, M. K., Filippov, A., … Telkki, V.-V. (2017). Structure and dynamics elucidation of ionic liquids using multidimensional Laplace NMR. Chem. Commun., 53(80), 11056–11059. https://doi.org/10.1039/c7cc05493a http://jultika.oulu.fi/Record/nbnfi-fe2017102750335 Javed, M. A., Komulainen, S., Daigle, H., Zhang, B., Vaara, J., Zhou, B., & Telkki, V.-V. (2019). Determination of pore structures and dynamics of fluids in hydrated cements and natural shales by various ¹H and ¹²⁹Xe NMR methods. Microporous and Mesoporous Materials, 281, 66–74. https://doi.org/10.1016/j.micromeso.2019.02.034 http://jultika.oulu.fi/Record/nbnfi-fe2019041712678 Komulainen, S., Roukala, J., Zhivonitko, V. V., Javed, M. A., Chen, L., Holden, D., … Telkki, V.-V. (2017). Inside information on xenon adsorption in porous organic cages by NMR. Chemical Science, 8(8), 5721–5727. https://doi.org/10.1039/C7SC01990D http://jultika.oulu.fi/Record/nbnfi-fe201709288804 Håkansson, P., Javed, M. A., Komulainen, S., Chen, L., Holden, D., Hasell, T., … Telkki, V.-V. (2019). NMR relaxation and modelling study of the dynamics of SF₆ and Xe in porous organic cages. Manuscript
25
Ageev, Sergei Z. "Application of density matrix methods to quadrupolar spins in solid state NMR and NQR." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq29870.pdf.
Full text
26
Dehner, Alexander. "Protein interactions studied by biochemical and NMR spectroscopic methods." [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972765476.
Full text
27
Hulst, Anthony Jacques Ronald Lambert. "New methods for the enantiomeric excess determination using NMR." [S.l. : Groningen : s.n. ; University Library of Groningen] [Host], 1994. http://irs.ub.rug.nl/ppn/.
Full text
28
Hughes, Leslie Peter. "Maximum entropy methods applied to NMR and mass spectrometry." Thesis, Durham University, 2001. http://etheses.dur.ac.uk/3785/.
Full textAbstract:
Maximum Entropy data processing techniques have been widely available for use by NMR spectroscopisis and mass spectrometrisls since they were first reported as a tool for enhancing damaged images. However, the techniques have been met with a certain amount of scepticism amongst the spectroscopic community; not least their apparent ability to get something for nothing. The aim of the work presented in this thesis is to demonstrate that if these techniques are used carefully and in appropriate situations a great deal of information can be extracted from both NMR and mass spectra. This has been achieved by using the Memsys5 and Massive Inference algorithms to process a range of NMR and mass spectra which suffer from some of the problems which are commonly encountered in spectroscopy, i.e. poor resolution, poor sensitivity, how to process spectra with a wide range of peak widths. The theory underlying the two algorithms is described simply and the techniques for selecting appropriate point spread functions are outlined. Experimental rather than simulated spectra are processed throughout. Throughout this work the Maximum Entropy results are freated with scepticism. A pragmatic approach is employed to demonstrate that the results are valid. It is concluded that the Maximum Entropy methods do have their place amongst the many other data processing strategies used by spectroscopists. If used correctly and in appropriate situations the results can be worth the investment in time needed to obtain a satisfactory result.
29
Briden, Sandra. "Development of methods of hair analysis using NMR spectroscopy." Thesis, University of Reading, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.629092.
Full textAbstract:
Forensic analysis of hair remains controversial and new methods of validation are persistently being sought. Although human hair has been the subject of chemical analysis for many years new approaches are always warranted by continual advances in technology. In this thesis a novel rapid and efficient method of hair analysis utilising microwave-assisted acid digestion to break the strong keratin bonds that dominate the hair matrix, coupled with 1 H NMR spectroscopic-based chemometric analysis, is described. Fingerprinting analysis of 265 such hair samples, using 1H NMR spectroscopy, generated peaks in the aliphatic, H. and aromatic regions of the NMR spectra. 1H NMR spectra allowed the determination of a number of metabolites, predominantly human proteinogenic amino acids. The number of peaks acquired in such 'H NMR spectra was large. It was found that the problem of analysing the number of variables present demanded a metabonomic approach in which digests of human hair were treated as a biofluid. Multivariate analysis (MVA) was applied to determine the possibility of identifying discriminatory compounds using principal component analysis (PCA). A comparison with geographical discriminatory factors allowed initial conclusions to be drawn with respect to the identity and relative levels of such metabolites, i.e. threonine. It is proposed that successful application of MVA has the advantage, in forensics, of overcoming bias due to the analyst's personal judgment. Progress in solid-state NMR spectroscopy has been rapid over recent years and hair samples were also subjected to the modern solid-state technique of cross polarization /magic angle spinning (CP-MAS) 13C NMR spectroscopic analysis. Solid-state NMR spectroscopy allows the analysis of samples with minimum sample preparation and with a simple chain of custody. The successful application of both solution-state metabonomics-based NMR and solid-state NMR analysis to hair analysis can be considered as a proof of principle.
30
Boland, Martin Peter. "Evaluation of solid-state NMR methods for drug discovery." Thesis, University of Manchester, 2005. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.549037.
Full text
31
Ibbett, D. A. "A developmental system for solid state NMR imaging." Thesis, University of Kent, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380989.
Full text
32
Sun, Han. "Stereochemistry of Challenging Natural Products Studied by NMR-based Methods." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2012. http://hdl.handle.net/11858/00-1735-0000-000D-FD1A-F.
Full text
33
Howarth, M. A. "Methods for the interpretation of proton NMR spectra of proteins." Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376918.
Full text
34
Dickson, Claire. "Improving NMR methods to solve 3D molecular structure in solution." Thesis, University of Bristol, 2018. http://hdl.handle.net/1983/7f93852e-3a5e-45b2-b8b3-23dc0694b601.
Full textAbstract:
Nuclear magnetic resonance (NMR) spectroscopy is an analytical technique that is used to probe the structure and dynamics of molecules. The relationships between measurable NMR properties and three-dimensional (3D) structure of small molecules were investigated using solution-state NMR spectroscopy with a focus on long-range proton-carbon scalar couplings (n>1JCH). The generation and validation of empirical equations to predict three-bond proton-carbon scalar couplings (3JCH) from 3D molecular structure were targeted. The accuracy of selected 2-dimensional methods for measuring n>1JCH in model compounds (strychnine and camphor) was assessed by comparison with 55 n>1JCH measured from coupled 13C spectra. The IPAP-based HSQMBC/HMBC methods offered a balance of experiment time, n>1JCH accuracy and number of measurable n>1JCH. However, to maximise the number of n>1JCH measured a combination of multiple experimental methods (coupled 13C, IPAP-HSQMBC and EXSIDE) was required. This led to an average 40% increase in the number of measured couplings compared to using any single technique. A fragment-based approach to empirical 3JCH prediction was developed by using density functional theory (DFT) to calculate 3JCH as a function of dihedral angle(s) for over 500 molecules. The fragments consisted of twelve different coupling pathways including saturated/unsaturated centres and β-heteroatoms and a variety of substituent patterns with a focus on the effect of methyl groups. The fragment-based approach and selected literature empirical equations were validated against experimentally measured and DFT-calculated 3JCH. This demonstrated that the fragment-based approach could be further improved by the inclusion of a general bond angle correction. Currently, DFT offers the most accurate 3JCH calculation with only basis set limitations on the breadth of 3JCH that can be calculated. However, the empirical methods offered >2800-fold time saving in the calculation of 3JCH compared to DFT when applied to strychnine, camphor and 2-ethyl-1-indanone.
35
Adams, Krysten Scott. "Using computational methods to predict NMR spectra for polyether compounds /." Electronic version (PDF), 2005. http://dl.uncw.edu/etd/2005/adamsk/krystenadams.pdf.
Full text
36
Hughes, Colan Evan. "New techniques in NMR spectroscopy." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297524.
Full text
37
Helgstrand, Magnus. "Structure determination of ribosomal proteins and development of new methods in biomolecular NMR." Doctoral thesis, Stockholm : Tekniska högsk, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3149.
Full text
38
Dancea, Felician. "New methods for automated NMR data analysis and protein structure determination." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=974442569.
Full text
39
Andronesi, Ovidiu-Cristian. "Solid-state NMR of (membrane) protein complexes novel methods and applications /." Doctoral thesis, [S.l.] : [s.n.], 2006. http://webdoc.sub.gwdg.de/diss/2006/andronesi.
Full text
40
Barrilero, Regadera Rubén. "Development of 1H-NMR Serum Profiling Methods for High-Throughput Metabolomics." Doctoral thesis, Universitat Rovira i Virgili, 2017. http://hdl.handle.net/10803/461603.
Full textAbstract:
El perfilat de sèrum per ressonància magnètica nuclear de protó (1H-RMN) està especialment indicat per a anàlisi a gran escala en estudis epidemiològics, nutricionals o farmacològics. L’espectroscòpia 1H-RMN requereix mínima manipulació de mostra i gràcies a la seva resposta quantitativa permet la comparació directa entre laboratoris. Un perfilat complet de sèrum per 1H-RMN requereix de tres mesures que es corresponen amb tres espècies moleculars diferents: lipoproteïnes, metabòlits de baix pes molecular i lípids. El perfilat de sèrum per 1H-RMN permet obtenir informació de grandària, nombre de partícules i contingut lipídic de les subfraccions lipoproteiques, així com l'abundància d'aminoàcids, productes de la glicòlisi, cossos cetònics, àcids grassos i fosfolípids, entre d'altres. No obstant això, la complexitat espectral afavoreix la inclusió d'errors en l'anàlisi manual de les dades, mentre que les múltiples interaccions moleculars en el sèrum comprometen la seva precisió quantitativa. És per tant necessari desenvolupar mètodes robustos de perfilat metabòlic per consolidar la 1H-RMN en la pràctica clínica. Per a això, aquesta tesi presenta diverses estratègies metodològiques i computacionals. En el primer treball, es van desenvolupar mètodes de regressió dels lípids del perfil lipídic clàssic, generalitzables a mostres de població sana i amb valors de lípids i lipoproteïnes anormals. Aquests lípids representen els principals indicadors de risc cardiovascular i els objectius terapèutics primaris. En el segon estudi caracteritzem els errors de quantificació en el perfilat 1H-RMN de metabòlits clínicament rellevants, que són deguts a la seva agregació a la proteïna sanguínia. També proposem un mètode que fomenta la competició per l'agregació i que ens permet obtenir quantificacions dels nostres metabòlits properes a les absolutes. Finalment, el tercer treball presenta LipSpin: una eina bioinformàtica de codi obert específicament dissenyada per al perfilat de lípids per 1H-RMN. A més, aquest estudi exposa alguns aspectes metodològics per millorar l'anàlisi de lípids per RMN.El perfilado de suero por resonancia magnética nuclear de protón (1H-RMN) está especialmente indicado para el análisis a gran escala en estudios epidemiológicos, nutricionales o farmacológicos. La espectroscopía 1H-RMN requiere mínima manipulación de muestra y gracias a su respuesta cuantitativa permite la comparación directa entre laboratorios. Un perfilado completo de suero por 1H-RMN requiere de tres mediciones que se corresponden con tres especies moleculares distintas: lipoproteínas, metabolitos de bajo peso molecular y lípidos. El perfilado de suero por 1H-RMN permite obtener información de tamaño, número de partículas y contenido lipídico de las subfracciones lipoproteicas, así como la abundancia de aminoácidos, productos de la glicólisis, cuerpos cetónicos, ácidos grasos y fosfolípidos, entre otros. Sin embargo, la complejidad espectral favorece la inclusión de errores en el análisis manual de los datos, mientras que las múltiples interacciones moleculares en el suero comprometen su precisión cuantitativa. Es por tanto necesario desarrollar métodos robustos de perfilado metabólico para consolidar la 1H-RMN en la práctica clínica. Para ello, esta tesis presenta varias estrategias metodológicas y computacionales. En el primer trabajo, se desarrollaron métodos de regresión de los lípidos del perfil lipídico clásico, generalizables a muestras de población sana y con valores de lípidos y lipoproteínas anormales. Estos lípidos representan los principales indicadores de riesgo cardiovascular y los objetivos terapéuticos primarios. En el segundo estudio caracterizamos los errores de cuantificación en el perfilado 1H-RMN de metabolitos clínicamente relevantes, que son debidos a su agregación a la proteína sanguínea. También proponemos un método que fomenta la competición por la agregación y que nos permite obtener cuantificaciones de nuestros metabolitos cercanas a las absolutas. Por último, el tercer trabajo presenta LipSpin: una herramienta bioinformática de código abierto específicamente diseñada para el perfilado de lípidos por 1H-RMN. Además, este estudio expone algunos aspectos metodológicos para mejorar el análisis de lípidos por RMN.
1H-NMR serum profiling is especially suitable for high-throughput epidemiological studies and large-scale nutritional studies and drug monitoring. It requires minimal sample manipulation and its quantitative response allows inter-laboratory comparison. A comprehensive 1H-NMR serum profiling consists of three measurements encoding different molecular species: lipoproteins, low-molecular-weight metabolites and lipids. 1H-NMR serum profiling provides information of size, particle number and lipid content of lipoprotein subclasses, as well as abundance of amino acids, glycolysis-related metabolites, ketone bodies, fatty acids and phospholipids, among others. However, the spectral complexity promotes errors in manual data analysis and the multiple molecular interactions within the sample compromise reliable quantifications. Developing robust methods of metabolite serum profiling is therefore desirable to consolidate high-throughput 1H-NMR in the clinical practice. This thesis presents several methodological and computational strategies to that end. In the first study, we developed generalizable regression methods for lipids in routine clinical practice (known as “lipid panel”), to be applied in healthy population and in a wide spectrum of lipid and lipoprotein abnormalities. These standard lipids are still the main measurements of cardiovascular risk and therapy targets. In the second study, we characterised the quantitative errors introduced by protein binding in 1H-NMR profiling of clinically-relevant LMWM in native serum. Then, we proposed a competitive binding strategy to achieve quantifications closer to absolute concentrations, being fully compatible with high-throughput NMR. Finally, the third study presents LipSpin: an open source bioinformatics tool specifically designed for 1H-NMR profiling of serum lipids. Moreover, some methodological aspects to improve NMR-based serum lipid analysis are discussed.
41
Pilger, Jens. "Development and application of NMR methods for challenges in drug discovery." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2013. http://hdl.handle.net/11858/00-1735-0000-0015-C6E8-4.
Full text
42
Lu, Hui. "Studies of protein folding and unfolding using NMR and optical methods." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337421.
Full text
43
Pooler, G. W. "Studies on drug molecules by theoretical methods, NMR and computer graphics." Thesis, City University London, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375823.
Full text
44
Ivchenko, Natala. "Phase cycling methods and spinning sideband manipulation in solid-state NMR." Thesis, University of Southampton, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414703.
Full text
45
Sanders, Kevin. "Development and application of new NMR methods for paramagnetic inorganic materials." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEN041/document.
Full textAbstract:
Une compréhension précise de la géométrie de coordination et de la structure électronique autour d’un ion métallique à l’intérieur des catalyseurs et des matériaux de batteries est essentielle pour contrôler ces systèmes complexes, modifier leur fonctionnement, et permettre la conception logique de sites améliorés. Cependant, la structure de ces systèmes n’est pas toujours accessible par des techniques de diffraction, et même si elle l’est, la structure électronique ne peut alors être déduite qu’indirectement des coordonnées atomiques. De ce fait, il est essentiel d’avoir une sonde directe de la structure électronique. L’objectif de cette thèse est l’étude des propriétés structurales et électroniques des sites mé- talliques de catalyseurs et de matériaux de batteries par Résonance Magnétique Nucléaire en rotation à l’angle magique (MAS NMR). La MAS NMR est une technique très performante pour l’étude des effets locaux dans les matériaux à l’état solide et permet de sonder directement la structure électronique des matériaux paramagnétiques à haute résolution. Néanmoins, cette ap- proche souffre d’une pauvre résolution et d’une sensibilité limitée pour les noyaux proches d’un site paramagnétique. Pour dépasser ces limitations, nous avons levé des verrous dans l’acquisition et l’interprétation de la MAS NMR en développant et appliquant de nouvelles méthodes pour l’étude de solides paramagnétiques basées sur des hautes fréquences de rotation (60-111 kHz MAS). Pour ce faire, un répertoire de séquences d’impulsion a été développé pour la détection et l’interprétation des effets paramagnétiques dans des solides cristallins et non cristallins. Le potentiel de cette méthodologie a été examiné pour l’élucidation de la géométrie locale et de la structure électronique autour des sites paramagnétiques de catalyseurs homogènes ou hétérogènes, et des matériaux de cathodes en phase mixte pour des batteries au Lithium. Nous voyons dans les méthodes présentées ici, un ensemble d’outils indispensables pour l’élucidation de nombreuses questions de la chimie moderne relatives à la structure et la fonction des sites métalliquesA precise understanding of the coordination geometry and electronic structure around metal cen- ters in catalysts and battery materials is crucial in order to control these complex systems, modify their behavior, and allow rational design of improved sites. However, such systems are not al- ways amenable for diffraction-based structural determination, and even if they are, obtaining atom-specific electronic structure can only be inferred indirectly from the atomic coordinates. As such, a direct probe of the electronic structure is highly desired. The aim of the present thesis is the investigation of structural and electronic properties of metal sites in catalysts and battery materials by magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. MAS NMR is a powerful technique for the investigation of local effects in solid materials, and offers a direct probe of highly resolved electronic structures in paramagnetic solids. However, it suffers from limited sensitivity and resolution for nuclei lying close to a paramagnetic center in general. We address these limitations by first tackling some of the bottlenecks in the acquisition and interpretation of MAS NMR by developing and applying new methodologies to paramagnetic solids using ultra-fast (60-111) kHz MAS rates. A "toolkit" of suitably designed pulse sequences is assembled for broadband detection and interpretation of paramagnetic shifts in crystalline and non-crystalline solids. The potential of this methodology is explored for the elucidation of local geometry and electronic structure around paramagnetic metal sites in homogeneous and heterogeneous catalysts, and a set of mixed-phase Li-ion battery cathode materials. We anticipate that the approaches described herein form an essential tool to elucidate many outstanding questions about the structure and function of metal sites in modern chemistry
46
Dey, Krishna K. "New Methods for Separating and Measuring Anisotropies in Solid State NMR." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1280972717.
Full text
47
Toumi, Ichrak. "Decomposition methods of NMR signal of complex mixtures : models ans applications." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4351/document.
Full textAbstract:
L'objectif de ce travail était de tester des méthodes de SAS pour la séparation des spectres complexes RMN de mélanges dans les plus simples des composés purs. Dans une première partie, les méthodes à savoir JADE et NNSC ont été appliqué es dans le cadre de la DOSY , une application aux données CPMG était démontrée. Dans une deuxième partie, on s'est concentré sur le développement d'un algorithme efficace "beta-SNMF" . Ceci s'est montré plus performant que NNSC pour beta inférieure ou égale à 2. Etant donné que dans la littérature, le choix de beta a été adapté aux hypothèses statistiques sur le bruit additif, une étude statistique du bruit RMN de la DOSY a été faite pour obtenir une image plus complète de nos données RMN étudiéesThe objective of the work was to test BSS methods for the separation of the complex NMR spectra of mixtures into the simpler ones of the pure compounds. In a first part, known methods namely JADE and NNSC were applied in conjunction for DOSY , performing applications for CPMG were demonstrated. In a second part, we focused on developing an effective algorithm "beta- SNMF ". This was demonstrated to outperform NNSC for beta less or equal to 2. Since in the literature, the choice of beta has been adapted to the statistical assumptions on the additive noise, a statistical study of NMR DOSY noise was done to get a more complete picture about our studied NMR data
48
Harris, Richard. "Development of NMR methods for conformational analysis of 13C-enriched oligosaccharides." Thesis, University of St Andrews, 1998. http://hdl.handle.net/10023/14226.
Full textAbstract:
The conformation and dynamics of sialyl Lewisx and related oligosaccharides were investigated using high resolution nuclear magnetic resonance measurements, and molecular dynamics calculations. In order to increase the number of structural parameters for inclusion in the molecular modelling simulations, the oligosacchaiide sialyl Lewisx was chemo-enzymatically synthesised to a high degree of carbon-13 enrichment (< 99%). The incorporation of labelling allows editing of standard homonuclear NMR experiments by the 13C chemical shift, thus overcoming the spectral overlap which plagues carbohydrate NMR. Three dimensional heteronuclear NOESY/ROESY-HSQC experiments have allowed the unambiguous assignment and quantitation of NOEs/ROEs in a number of oligosaccharides including evidence that the anti-conformer is populated in aqueous solution for the Gal 1- 4GlcNAc linkage in sialyl 2,3-N-acetyllactosamine trisaccharide. Additional structural information was gained from the measurement of trans-glycosidic three bond carbon- carbon coupling constants. A Karplus relationship was derived for the C-O-C-C fragment allowing the back-calculation of 3Jcocc values from molecular dynamics simulation for comparison to experimental data. Additional distance restraints were derived from NOEs to exchangeable protons in low temperature studies using a mixed solvent system of H2O/acetone-d6. The increase in the number of distance restraints, have allowed the use time-averaged molecular dynamics simulations, and from these it is shown that NOEs to certain hydroxyls in sialyl Lewisx can only be explained if these hydroxyls are constrained within hydrogen bonds.
49
Bennett, Graham. "Quantitative analysis using low resolution NMR." Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299565.
Full text
50
Aluas, Mihaela. "Characterization of rubber filled polymers by solid state NMR spectroscopy and other methods." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=975655663.
Full text