15N-NMR Spectroscopy


Book Description

After the proton and carbon, nitrogen is, with oxygen, the most impor tant atom in organic and especially bioorganic molecules. However, the development of nitrogen spectroscopy is indeed very recent. This is due to the fact that nitrogen-14, which is the naturally abundant iso tope, suffers, for structural studies, from the disadvantages inherent in nuclei with a quadrupolar moment (Table 1.1). Actually, indirect 15N measurements were reported in the early days of double resonance spectroscopy and the first direct detection of 15N resonance signals at the natural abundance level was realized in 1964 (R 17) at 4.33 MHz 1 (~ 1T) using a 15 mm o.d. cell in the field sweep mode (~ 0.16 min- ). Signal-to-noise ratios only of 3-4 were obtained for neat liquids and this low sensitivity of the 15N resonance still remains the main dis advantage for 15 spectroscopy (Table 1.1). However, nitrogen-15 has, N probably more than any other nucleus, benefited from the advances of NMR technology, i.e. Fourier transformation, multinuclear facilities, wide-bore super conducting solenoids, and, with the new generation of spectrometers, 15N-NMR is entering the field of routine investigation. Nevertheless, in spite of these spectacular improvements, obtaining 15N spectra of diluted species or large biochemical molecules is often not very easy and a good knowledge of the relaxation properties pecu liar to 15N may be necessary in order to adjust the pulse sequences and the decoupler duty cycle correctly (Section 2).










The Multinuclear Approach to NMR Spectroscopy


Book Description

The field of nuclear magnetic resonance has experienced a number of spectacular developments during the last decade. Fourier transform methodology revolutionized signal acquisition capabilities. Superconducting magnets enhanced sensitivity and produced considerable improvement in spectral dispersion. In areas of new applicat ions, the life sciences particularly bene fited from these developments and probably saw the largest increase in usage. NMR imaging promises to offer a noninvasive alternative to X rays. High resolution is now achievable with solids, through magic angle spinning and cross polarization, so that the powers of NMR are applicable to previously intractable materials such as polymers, coal, and other geochemicals. The ease of obtaining relaxation times brought an important fourth variable, after the chemical shift, the coupling constant, and the rate constant, to the examination of structural and kinetic problems i~ all fields. Software development, particularly in the area of pulse sequences, created a host of useful tech niques, including difference decoupling and difference nuclear Overhauser effect spectra, multidimensional displays, signal enhancement (INEPT), coupling constant analysis for connectivity (INADEQUATE), and observation of specific structural classes such as only quaternary carbons. Finally, hardware development gave us access to the entire Periodic Table, to the particular advan tage of the inorganic and organometallic chemist. At the NATO Advanced Study Institute at Stirling, Scotland, the participants endeavored to examine all these advances, except imaging, from a multidisciplinary point of view.




Applications of NMR Spectroscopy


Book Description

Applications of NMR Spectroscopy is a book series devoted to publishing the latest advances in the applications of nuclear magnetic resonance (NMR) spectroscopy in various fields of organic chemistry, biochemistry, health and agriculture. The fifth volume of the series features several reviews focusing on NMR spectroscopic techniques for identifying natural and synthetic compounds (polymer and peptide characterization, GABA in tinnitus affected mice), medical diagnosis and therapy (gliomas) and food analysis. The spectroscopic methods highlighted in this volume include high resolution proton magnetic resonance spectroscopy and solid state NMR.




Nitrogen NMR


Book Description

To date nitrogen NMR has been discussed in research papers and review articles throughout the scientific literature. It has been our aim in preparing this book to provide a comprehen sive account of the widely spread applications of nitrogen NMR. The relevant literature has been surveyed from the beginnings of NMR until early 1972. The steady annual growth in the number of references cited since 1965 is ample evidence of the ever increasing importance of the subject. Sufficient theoretical and experimental background is given for an understanding of the applications dealt with in later chapters. The basic principles of NMR are developed with a theoretical approach to chemical shifts and spin-spin coupling constants, particular emphasis being given to nitrogen nuclei. Following this the experimental aspects of nitrogen NMR are adequately described. Special emphasis is given to the observable effects of the nuclear quadrupole moment of the 14 N nucleus. It is appro priate that this topic be dealt with in depth since quadrupolar interactions frequently dominate the information available from a study of the 14 N nucleus and other nuclei spin coupled to it. The applications of nitrogen chemical shift data to organic and inorganic molecules are covered in two extensive chapters which include the effects of paramagnetism on nitrogen NMR.




Biological NMR Spectroscopy


Book Description

This book presents a critical assessment of progress on the use of nuclear magnetic resonance spectroscopy to determine the structure of proteins, including brief reviews of the history of the field along with coverage of current clinical and in vivo applications. The book, in honor of Oleg Jardetsky, one of the pioneers of the field, is edited by two of the most highly respected investigators using NMR, and features contributions by most of the leading workers in the field. It will be valued as a landmark publication that presents the state-of-the-art perspectives regarding one of today's most important technologies.