The Application of Dynamic Nuclear Polarization Enhanced NMR to Non-equilibrium Systems PDF Download

Author: Sean Michael Bowen
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Nuclear magnetic resonance (NMR) yields remarkably detailed structural information about virtually any molecule. However, its application to non-equilibrium systems is hampered by a lack of sensitivity. To increase the amount of signal that can be obtained from a NMR experiment, various hyperpolarization schemes have been previously introduced. One such technique is dynamic nuclear polarization (DNP), which can enhance NMR sensitivity by several orders of magnitude. The work detailed here focuses on the development of methods utilizing DNP to study non-equilibrium systems such as chemical and biochemical reactions in real-time. To work with hyperpolarized samples, we have designed and constructed a rapid injection and mixing system. This system allows samples to be transported between superconducting magnets used for polarization and for NMR spectroscopy in less than two seconds. Rapid transport is essential for successful use of samples with short spin-lattice relaxation times. For the study of reactions under non-equilibrium conditions, the system provides the additional capability for samples to be mixed with a second, unpolarized reagent. A chromogenic trypsin catalyzed ester hydrolysis reaction was used to validate the DNP-NMR technique as a tool for kinetic analysis. It is shown that the DNP-NMR method agrees with the conventional UV method within the uncertainty of the measurement. Hyperpolarization in this modality presents both challenges and opportunities, each of which motivate the development of new NMR techniques. In addition to the determination of kinetics, DNP-NMR is amenable to mechanistic analysis of a reaction. We have developed a technique based on selective inversion of spin-polarization, which allows for mapping of atoms between reactant and product of a reaction. This scheme was applied to a Grignard reaction, demonstrating applicability to organic reactions. Signal averaging, as it is applied for conventional multi-dimensional correlation spectroscopy cannot always be applied easily when using hyperpolarized sample. For the rapid measurement of heteronuclear correlation spectra, we have developed a technique utilizing the differential scaling of scalar coupling under off-resonance irradiation. Although DNP-NMR yields spectra of outstanding quality even with small quantities of sample, peak intensities are not quantitative. It is nevertheless possible to compare peak multiplets obtained from fractionally isotope labeled samples. Using biosynthetically labeled lipids from E. Coli cells, we showed that the resulting labeling patterns reflect their biosynthetic pathways. As a final case-study employing several of these newly developed methods, the uronate isomerase catalyzed isomerization of glucuronate into fructuronate was studied. The ability to follow the reaction in real-time while directly observing all anomeric forms of the reactant and product permits the independent determination of kinetics for each anomeric form of substrate and product. This study revealed the anomeric specificity of the enzyme.

Author: Vladimir K. Michaelis
Publisher: John Wiley & Sons
ISBN: 1119441668
Category : Science
Languages : en
Pages : 920

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Book Description
Addresses Dynamic Nuclear Polarization (DNP) as a technique for sensitivity-enhancement in solid-state NMR spectroscopy This comprehensive handbook is a compendium of the current state-of-the art of high field Dynamic Nuclear Polarization—from long-proven, early developments, up to today’s hot topics. It covers all the relevant subjects that have made a direct or indirect contribution toward advancing this field, and focuses on topics such as: the theory behind the effects seen within DNP; instrumentation required for carrying out DNP; and specific applications of DNP including protein monitoring, catalysis, nanoparticles, biological and clinical studies. Development and application of techniques that have indirectly contributed to advancing MAS DNP NMR, such as DNP experiments on static solids within microwave resonant structures, and high-field EPR, are also examined. Handbook of High Field Dynamic Nuclear Polarization is presented in three sections—Theoretical Aspects, DNP Development (instrumentation / radical / sample), and DNP NMR Applications. The first section offers chapters on; solid and cross effect DNP; thermal mixing; Overhauser; and dissolution DNP. The second looks at: microwave technology, gyrotron, and IOE; homebuilt and commercial DNP spectrometers; and glassing vs. solvent-free DNP. The final section provides information on; amyloid, membrane, and nanocrystalline proteins; metals, and surface enhanced DNP; pharmaceuticals; nanoparticles; and much more. Covers one of the biggest developing fields in magnetic resonance Relevant to students, academics, and industry within the physical, materials, medical, and biochemical sciences An excellent starting point and point-of-reference for researchers in the field Edited by a widely respected team with contributions from key researchers in the NMR community Part of the eMagRes Handbook Series Handbook of High Field Dynamic Nuclear Polarization is an ideal reference for all researchers and graduate students involved in this complex, interdisciplinary field. About eMagRes Handbooks eMagRes publishes a wide range of online articles on all aspects of magnetic resonance in physics, chemistry, biology and medicine. The existence of this large number of articles, written by experts in various fields, is enabling the publication of a series of eMagRes Handbooks on specific areas of NMR and MRI. The chapters of each of these handbooks will comprise a carefully chosen selection of eMagRes articles. In consultation with the eMagRes Editorial Board, the eMagRes Handbooks are coherently planned in advance by specially-selected Editors, and new articles are written to give appropriate complete coverage. The handbooks are intended to be of value and interest to research students, postdoctoral fellows and other researchers learning about the scientific area in question and undertaking relevant experiments, whether in academia or industry. Have the content of this Handbook and the complete content of eMagRes at your fingertips! Visit: www.wileyonlinelibrary.com/ref/eMagRes

Author: Christopher Parish
Publisher:
ISBN:
Category : Cancer
Languages : en
Pages :

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Nuclear magnetic resonance (NMR) spectroscopy of nuclei with low magnetic moments such as 13C spins can be quite challenging and time-consuming. Dynamic nuclear polarization (DNP) via the dissolution method greatly alleviates this sensitivity problem by enhancing the NMR signals of these insensitive nuclei by several thousand-fold. Dissolution DNP thus allows 13C NMR tracking of cellular metabolism in living cells in real-time with superb sensitivity and high specificity. Herein, the bulk of my PhD dissertation work has been devoted to the elucidation and optimization of chemical physics of DNP technology in pursuit of attaining the highest NMR signal enhancements. One finding highlighted in this dissertation is the confirmation that the solidstate 13C DNP efficiency is affected by the isotopic location of the 13C label within the target molecule. Such can be explained via the thermal mixing model of DNP. Another major work in this dissertation is the investigation of the effects of 2H enrichment of the glassing solvents on the solid-state 13C spin-lattice T1 relaxation times of hyperpolarized 13C acetate. It is reported herein that glassing solvent deuteration elongates the 13C T1 relaxation times significantly, indicative of reduced intermolecular dipolar interaction of 13C spins with 2H spins compared to coupling with 1H spins. Next, this dissertation also encompasses two studies regarding the effect upon DNP of doping samples with mixtures of two different free radicals as opposed to doping them with one type of free radical. In one of the two studies, it was determined that a mixture of the wide EPR width 4-oxo-TEMPO and narrow EPR width trityl OX063 yields interesting 13C DNP results. There appears to be competing effects when the microwave irradiation frequency was set to the negative polarization peak of trityl OX063 which coincides with the positive polarization peak of 4-oxo-TEMPO. On the other hand, a mixture of both narrow EPR widths trityl and BDPA free radicals yields an additive effect. Finally, this dissertation also details the use of 13C NMR in the characterization of 13C-labelled amino acids and their application in investigating cancer cell metabolism. 13C-labeled amino acids are potential hyperpolarized 13C NMR spectroscopy and imaging (MRI) metabolic probes for cancer because a number of metabolic pathways that involve these biomolecules are abnormal in tumors. For instance, the enzyme branched chain amino acid transferase (BCAT), which catalyzes the conversion of branched chain amino acids (BCAA) to their ketoacid counterparts or vice versa, is overexpressed in several cancers. In this project, [1- 13C] L-leucine and [1- 13C] alpha-ketoisocaproate (KIC) were used to study the aberrant BCAT metabolic activity in glioblastoma. SfXL glioblastoma cells appear to preferentially convert 13CKIC to 13C leucine rather than vice versa. Western blot experiments confirmed that BCAT expression is higher in SfXL cells than in normal astrocytes. Overall, this dissertation details the chemical tuning methods in DNP that I have unraveled in pursuit of attaining the highest 13C NMR signal enhancements. These optimized DNP signals are crucial to the success of in vivo NMR or MRI studies, particularly in probing the hyperactive metabolism of cancer.

Author: Qing Wang
Publisher:
ISBN:
Category : Nuclear magnetic resonance
Languages : en
Pages :

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Book Description
Nuclear magnetic resonance (NMR) is a phenomenon that describes the microscopic environment of nuclear spins under the external magnetic field by applying radiofrequency waves at their corresponding nuclear Larmor frequency, and widely used in materials science, biochemistry, and medical imaging. It allows one to investigate molecular structural information and dipolar intramolecular interactions noninvasively. However, the majority of the nuclei are insensitive to NMR spectrometer and exhibit minute NMR signals due to their intrinsic weak nuclear magnetic moments. This low signal-to-noise issue has been mitigated by an approach called dynamic nuclear polarization (DNP) in which the high polarization of electron spins is transferred to the nuclei via microwave irradiation close to electron Larmor frequency at high magnetic field and low temperature. To harness this enhanced NMR signal for biomedical or chemical applications, the dissolution process is employed wherein the frozen polarized nuclei samples are rapidly dissolved into hyperpolarized liquids at physiological temperatures. Using this technology, the NMR signals of weak nuclei such as 13C and 89Y can be enhanced by several thousand-fold relative to their thermal equilibrium NMR signals. The bulk of this PhD dissertation entails a discussion of the details of DNP physics and applications of hyperpolarized low-gamma nuclei such as 13C-enriched organic compounds and 89Y-complexes that have chemical and biological relevance. Furthermore, this thesis also involves a discussion the construction of a homebuilt cryogen-free and variable-field DNP instrumentation. This DNP instrumentation is a major leap in the field of hyperpolarization since it does not require expensive liquid helium for DNP operation. As such, this instrumentation allowed us to measure, for the first time, the solid-state T1 relaxation times of 13C compounds at 1.8 K in the 0-9 T magnetic field range. The main finding of this measurement is that the 13C T1 relaxation times of carboxylates follow a power law dependence on magnetic field according to T1~B2-3 at cryogenic temperature. Meanwhile, the feasibility of hyperpolarized 89Y-EDTMP and 89Y-DTPMP as potential chemical shift-based NMR sensors for pH was studied. The results of this study show that hyperpolarized 89Y-EDTMP has a relatively wide chemical shift range of 16 ppm over pH 5-9 range with pKa close to neutral—a promising pH sensor for future in vivo applications. In addition, dissolution DNP also allows one to track the complexation of free Y3+ ion and ligand such as DOTA in realtime under certain buffered solution conditions, giving insight as a model for Gd3+ complexation with specific macrocyclic ligands. Furthermore, dissociation of 89Y-DTPA into free 89Y ion and DTPA ligand in the presence of Zn2+ in the solution has been monitored in real-time, providing a direct chemical reaction monitoring process for the complex. Additionally, the effect of 13C nuclear spin density of 13C DNP signal and T1 relaxation was also investigated. Finally, this thesis also includes a 13C/15N NMR investigation of alanine metabolism in glioblastoma cells. In summary, this PhD dissertation encompasses a discussion of the analytical power of hyperpolarized and conventional NMR spectroscopy in the investigation of chemical and biological systems.

Author: Lars T. Kuhn
Publisher: Springer
ISBN: 364239728X
Category : Science
Languages : en
Pages : 311

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Elucidating Organic Reaction Mechanisms using photo-CIDNP Spectroscopy, by Martin Goez. Parahydrogen Induced Polarization by Homogeneous Catalysis: Theory and Applications, by Kerstin Münnemann et al. Improving NMR and MRI Sensitivity with Parahydrogen, by R. Mewis & Simon Duckett. The Solid-state Photo-CIDNP Effect, by Jörg Matysik et al. Parahydrogen-induced Polarization in Heterogeneous Catalytic Processes, by Igor Koptyug et al. Dynamic Nuclear Polarization Enhanced NMR Spectroscopy, by U. Akbey & H. Oschkinat. Photo-CIDNP NMR Spectroscopy of Amino Acids and Proteins, by Lars T. Kuhn.

Author: Björn Dollmann
Publisher: Sudwestdeutscher Verlag Fur Hochschulschriften AG
ISBN: 9783838125602
Category :
Languages : en
Pages : 192

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Book Description
Nuclear magnetic resonance (NMR) is a versatile technique relying on spin-bearing nuclei. Since its discovery more than 60 years ago, NMR and related techniques have become indispensable tools with innumerable applications in physics, chemistry, biology and medicine. One of the main obstacles in NMR is its notorious lack of sensitivity, which is due to the minuscule energy splitting of the nuclear spins at room temperature. Appropriately, the inherent low polarization allows for a theoretical sensitivity enhancement of more than 10,000. The NMR signal enhancement of protons which can be achieved by means of Dynamic Nuclear Polarization (DNP) is approximately 660. In this book, different hardware aspects and polarizing agents for DNP were studied. The results show the potential of DNP, especially at a magnetic field of B=0.35 T, when it comes to the polarization of nuclei with a very low magnetogyric ratio which should result in many new applications. These presented components and designs could be the foundation to open up the application of a mobile DNP polarizer for medical applications.

Author: Gregory S. Nusinovich
Publisher: JHU Press
ISBN: 1421429411
Category : Science
Languages : en
Pages : 352

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Book Description
As unique sources of coherent high-power, microwave, and millimeter-wave radiation, gyrotrons are an essential part of the hunt for controlled fusion. Presently, gyrotrons are actively used for electron cyclotron resonance plasma heating and current drive in various controlled fusion reactors. These sources have been under development in many countries for more than forty years. In spite of their widespread use, however, there is as yet no single book to introduce non-specialists to this vital field. Now Gregory S. Nusinovich, an early pioneer of the gyrotron and widely regarded today as the world's leading authority on the subject, explains the fundamental physical principles upon which gyrotrons and related devices operate. Nusinovich first sets forth some "rules of thumb" that allow readers to understand gyrotron operation in simple terms. He then explores the fundamentals of the general theory of gyrotrons and offers an overview of the various types of gyro-devices, including gyromonotrons, gyroklystrons, gyro-traveling-wave tubes, and gyrotwystrons. He explains not only the theory, linear and nonlinear, but also the practical challenges that users of such devices face. This book will be of interest to undergraduate and graduate students as well as to those who develop gyrotrons or who use them in various applications. It should also appeal to plasma physicists interested in charged-particle dynamics, as well as to applied physicists needing to know more about micro- and millimeter-wave technologies.

Author: C. Richard
Publisher: Springer Science & Business Media
ISBN: 3642657931
Category : Science
Languages : en
Pages : 126

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Book Description
Anomalous electron-spin state populations in the Electron Paramagnetic Re sonance (EPR) spectra of radicals formed during radio lysis experiments were observed in 1963 by FESSENDEN and SCHULER [170a]. This phenomenon did not receive much attention at the time. In 1967, BARGON, FISCHER, and JOHNSEN [5] and independently WARD and LAWLER [7,8] reported a similar phenomenon for Nuclear Magnetic Resonance (NMR) spectra taken during radical reactions: emission or enhanced absorption, or both. The earliest attempts to explain this new NMR phenomenon treated these effects in a way similar to that of Dynamic Nuclear Polarization (DNP) or the Overhauser effect. Although the polarization has a completely different origin, DNP gave its name to this effect: Chemically Induced Dynamic Nuclear Polariza tion (CIDNP). [The name Chemically Induced Dynamic Electron Polarization (CIDEP) was introduced later by analogy with CIDNP]. After the initial publica tions, all the new data demonstrated that the first theory could not be correct. In 1969, a new theory was proposed by CLOSS [18] and independently by KAPTEIN and OOSTERHOFF [23] and called the radical-pair theory. This mechanism was proposed to account for the observations of polarization in both NMR and EPR. The radical-pair theory is based on weak interactions in a pair of radicals: the strength of interaction between the electronic states of the radicals depends in particular on the nuclear-spin states.

Author: Andrew Byron Casey
Publisher:
ISBN:
Category :
Languages : en
Pages : 104

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Book Description
Solid State NMR (SSNMR) can determine molecular as well as supermolecular structure and dynamics. The low signal intensities make many of these experiments prohibitively long. Dynamic Nuclear Polarization provides a method of enhancing signal intensities and reducing experimental time. DNP requires transferring polarization from unpaired electrons to nuclei. Driving this transfer requires irradiation with high power microwaves which are generated with gyrotrons oscillators. We describe a series of modifications are made to an existing 140 GHz gyrotron allows for continuous wave operation and higher power and greater stability. DNP mechanisms are primarily limited to SSNMR. A method of using DNP to enhance liquid state NMR spectra is described. Signal enhancements of over 100 are reported for a solution of glucose. To obtain maximum DNP enhancements microwave irradiation times of up to 40 s are often required. While this increases your signal intensity for a single scan it decreases the gain from signal averaging for a given time. A method of choosing the optimum irradiation time is presented. DNP enhancements in continuous wave experiments exhibit an inverse field dependence. There are several pulsed DNP experiments exhibit no field dependence. To further study these techniques a pulsed 9 GHz EPR spectrometer has been assembled.

Author: Peter James Niedbalski
Publisher:
ISBN:
Category : Carbon
Languages : en
Pages :

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Book Description
Nuclear magnetic resonance (NMR) is a technique that probes the microscopic environment of molecules by investigating the interaction between nuclear magnetic moments and the magnetic field in which they reside. Nuclear magnetic moments, however, are very weak, causing the Boltzmann polarization of nuclei and hence the NMR signal to be very small. This may be resolved through the use of dynamic nuclear polarization (DNP), a process by which high electron polarization is transferred to nuclei through microwave irradiation near the electron resonance. In this work, primary focus is given to dissolution DNP in which nuclei are highly polarized at cryogenic temperature and then rapidly dissolved with a superheated solvent. This process results in a liquid sample whose NMR signal is enhanced many thousand-fold over thermal equilibrium. While applications of this technique are abundant, there are many unanswered questions surrounding the underlying physics and methods of optimization of the DNP process. In this work, some of these open questions are investigated through development of instrumentation and exploration of DNP free radicals. In particular, the construction of two high magnetic field DNP polarizers are discussed, one of which is the first of a new generation of cryogen-free polarizers. Furthermore, the water soluble DNP free radicals TEMPO and trityl are thoroughly investigated with a specific emphasis on the addition of paramagnetic ion complexes. Over the course of these experiments, several paramagnetic agents were tested for the first time and proven to be effective to a similar degree as the field standard gadolinium. Additionally, the link between shortened electronic T1 and improved DNP efficiency was con firmed through the study of transition metal complex dopants to DNP. A number of supporting experiments are also discussed, including Earth's field NMR and classification of free radicals by UV-Vis spectrophotometry and electron paramagnetic resonance. Finally, several basic molecular imaging applications of dissolution DNP are presented highlighting one of the many possible uses of hyperpolarized 13C NMR spectroscopy. Ultimately, this dissertation presents and discusses a number of novel methods by which 13C dynamic nuclear polarization may be optimized, paving the way for further study into the physics and applications of this technique.