Resonance assignment chemical shift prediction

A full assignment of the proton resonance of substituted 2-styryl-5-nitroimidazoles was carried out by the use of an addition increment method for chemical shift prediction [353]. Some 4-styryl-5-nitroimidazoles have been studied in [354],... 

In the absence of sequence-specific protein NMR resonance assignments, the data used for NOE matching are limited to the unassigned experimental protein H and 13C chemical shifts, the predicted protein H and 13C chemical shifts, and the experimental and predicted... 

Empirical as well as ab-initio quantum mechanical calculations of chemical shifts are likely to become an important tool for resonance assignments. Specifically, the ab-initio-type calculations are likely to prove useful in predicting conformations of polymorphs by comparing the, derived from guessed 3-D molecular structure inputs, with experimental chemical shifts. 

The MAPPER procedure [39] has been suggested to alleviate this problem. This procedure is based upon the average chemical shifts of each amino acid type and its standard deviation. It ranks possible assignments according to their probabilities based on their chemical shift statistics. However, the NMR investigation of protein kinases is made easier if the X-ray structure of the particular kinase is available. For a protein with known structure it is possible to predict chemical shifts quite accurately [40]. The chemical shift matching procedure uses these chemical shift values instead of a statistical input of normally distributed standard resonances. 

The data suggest that both CF2 and CFCI fluorines contribute to the resonances between -121.4 and -122.0 ppm. The /pp couplings prove the existence of CFj fluorines in this region. The presence of CFCl fluorines can be confirmed by the HMQC data. Finally, Carnevale et al. used density functional theory (DFT) calculations to predict the relative chemical shifts of 9 and 10. As a consequence, they were able to assign the two sets of resonances to their respective stereoisomers. 

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