Nuclear magnetic resonance structural analysis

Laurence, J. S., LiWang, A. C., and LiWang, P. J. (1998). Effect of N-terminal trucation and solution conditions on chemokine dimer stability nuclear magnetic resonance structural analysis of macrophage inflammatroy protein lb mutants. Biochemistry 37, 9346-9354. 

T. Charpentier, P. Kroll, F. Mauri, First-principles nuclear magnetic resonance structural analysis of vitreous silica. J. Phys. Chem. C 113,7917-7929 (2(X)9)... 

The molecular structure determinations of 4 <1996JME2922> and 5 <1997EJM241> by X-ray diffraction, molecular modeling, and nuclear magnetic resonance (NMR) analysis were reported (Figure 2). 

Correct mass of purified proteins is determined using matrix-assisted laser desorption ionization-time of flight (MALDI-TOF). N-terminal sequencing and/ or LC-ES-MS can verify correct amino acid sequence. Folding of the recombinant protein should be compared to the natural counterpart by measuring CD-spectra. Furthermore, nuclear magnetic resonance (NMR) analysis can be performed to ensure the presence of tertiary structure, important for IgE binding activity (Neudecker et al. 2003). 

Fig. 9. Structures of homopumiliotoxins from dendrobatid frogs and bufonid toads. The structure of homopumiliotoxin 223G is based on nuclear magnetic resonance spectral analysis (77). The absolute configuration is unknown. Homopumiliotoxin 223G occurs in dendrobatids (77), ranids (73), and bufonids (8 ), while the other alkaloids have been detected only in the bufonid toads (Melanophryniscus) (81).

A major class of amphibian alkaloids was recently discovered in frogs of the myobatrachid genus Pseudophryne (86,119). These represent the unidentified indolic compounds first noted by Erspamer and co-workers in 1976 (169). Isolation of two of these indole alkaloids from partially purified extracts of Pseudophryne coriacea allowed structure elucidation of pseudophrynaminol (XIV) and pseudophrynamine A (XV) by nuclear magnetic resonance spectral analysis (119). Methoxide cleavage of pseudophrynamine A yielded pseudophrynaminol and a methyl ester... 

Isolation of sufficient 235C for nuclear magnetic resonance spectral analysis will be necessary to confirm the proposed structure. Alkaloid 235C is a minor alkaloid in Mantella aurantiaca and Mantella crocea (73). 

Derivatization with a CDA results in the chemical modification of the analytes. It is important, therefore, to ascertain that the expected products are obtained. Thus, when a new derivatization reaction is carried out or a new CDA is first used, it is essential to confirm rigorously the structure of the derivatives using appropriate analytical techniques (mass spectrometry, nuclear magnetic resonance, elemental analysis, etc.). This is particularly important in complex cases, for example, when more than one functional group in the analyte may react with the CDA. 

On the basis of theoretical calculations and also from the gas chromatography (GC) analysis, hydroxyl number and nuclear magnetic resonance (NMR) analysis results, it has been confirmed that the reactive high MW diol present in the technical grade materials has the structure ... 

Medical Imaging. An area in which applied mathematics has become fundamentally important is the field of medical imaging, especially as it applies to magnetic resonance imaging (MRI). The MRI technique developed from nuclear magnetic resonance (NMR) analysis commonly used in analytical chemistry to determine molecular structures. In NMR, measurements are obtained of the absorption of specific radio frequencies by molecules held within a magnetic field. The strength of each absorption and specific patterns of absorptions are characteristic of the structure of the particular molecule and so can be used to determine unequivocally the exact molecular structure of a material. 

The structure of SPEKs was usually determined by nuclear magnetic resonance (NMR) analysis. For each analysis, 3 wt.% polymer solution was prepared in deuterated dimethyl sulfoxide (DMSO-tfg) for HNMR and 15 wt.% for CNMR. The chemical shift of tetramethylsilane was used as the internal standard reference. The typical HNMR spectrum and its chemical shift assignment for SPEEK obtained by the postsulfonation method are also shown in Figure 5.14. 

One has seen that the number of individual components in a hydrocarbon cut increases rapidly with its boiling point. It is thereby out of the question to resolve such a cut to its individual components instead of the analysis by family given by mass spectrometry, one may prefer a distribution by type of carbon. This can be done by infrared absorption spectrometry which also has other applications in the petroleum industry. Another distribution is possible which describes a cut in tei ns of a set of structural patterns using nuclear magnetic resonance of hydrogen (or carbon) this can thus describe the average molecule in the fraction under study. 

Abscisin II is a plant hormone which accelerates (in interaction with other factors) the abscission of young fruit of cotton. It can accelerate leaf senescence and abscission, inhibit flowering, and induce dormancy. It has no activity as an auxin or a gibberellin but counteracts the action of these hormones. Abscisin II was isolated from the acid fraction of an acetone extract by chromatographic procedures guided by an abscission bioassay. Its structure was determined from elemental analysis, mass spectrum, and infrared, ultraviolet, and nuclear magnetic resonance spectra. Comparisons of these with relevant spectra of isophorone and sorbic acid derivatives confirmed that abscisin II is 3-methyl-5-(1-hydroxy-4-oxo-2, 6, 6-trimethyl-2-cyclohexen-l-yl)-c s, trans-2, 4-pen-tadienoic acid. This carbon skeleton is shown to be unique among the known sesquiterpenes. 

C Nuclear Magnetic Resonance Spectra. The sohd-state CNMR spectra of 6,7-dimethyl-2,3-di(pyridin-2-yl)quinoxahne (130) and its salts have been used to complement X-ray information (see above) on fine structure. A study of the spectra of mono- to tetramethylquinoxalines has made possible the analysis of mixtures of such methylated quinoxalines obtained from ambiguous primary syntheses. 

FIG. 23 Comparison of various one-parameter diffusion models. (Reproduced with permission from Ref. 448, Analysis of Diffusion and Structure in Polyacrylamide Gels by Nuclear Magnetic Resonance, M.S. Thesis, Florida State University, Copyright 1997, Brigita Penke.)... 

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