نتایج جستجو برای: nmr spectra
تعداد نتایج: 160021 فیلتر نتایج به سال:
The assignment of resonances in the complex NMR spectrum of a protein is the first step in any study of protein structure, function or dynamics. Prior to 1980, assignment was achieved using 1D NMR, and based, for the most part, on the assumption that the structure of the protein in solution was the same as in the X-ray structure. The introduction of 2D NMR techniques such as COSY and NOESY in t...
Nuclear magnetic resonance (NMR) spectra of spin systems polarized either thermally or by parahydrogen exhibit strikingly different field dependencies. Thermally polarized spin systems show the well-known roof effect, observed when reducing magnetic field strengths which precludes the independent determination of chemical shift differences and J-coupling constants at low-fields. Quantum mechani...
Prerequisites for the quantification of cerebral metabolite concentrations by NMR are a proper assignment of pertinent resonances and the identification of components with overlapping signals. The purpose of this study is to more closely examine the nature of the strong N-acetyl methyl signal that is observed in 'H NMR spectra of mammalian brain and commonly ascribed to N-acetylaspartate (NAA)....
Flow scintillation analysis is commonly used to quantify the radioisotope label on organic compounds such as biochemicals, drugs, and metabolites separated from complex mixtures by High Performance Liquid Chromatography (HPLC). The subsequent task of determining the molecular structure of the separated substances can be formidable. Traditional methods of structure determination involve collecti...
The revision of the structure of the sesquiterpene aquatolide from a bicyclo[2.2.0]hexane to a bicyclo[2.1.1]hexane structure using compelling NMR data, X-ray crystallography, and the recent confirmation via full synthesis exemplify that the achievement of "structural correctness" depends on the completeness of the experimental evidence. Archived FIDs and newly acquired aquatolide spectra demon...
Introduction NMR spectra can be recorded by displaying the intensity of absorption not only as a function of one frequency but also as a function of a second or third variable. This original idea has been suggested by Jeener in 1971 [1] and since then the basic principles and some pioneer experiments of multidimensional NMR spectroscopy have been developed by several groups [2, 3]. In particula...
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