the nmr spectra of azo dyes, 5-arylazobarbituric (5a-g), 5-arylazo-1,3-dimethylbarbituric(6a-g) and 5-arylazothiobarbituric acids (7a-g) were studied in dmso-d6 in differentconcentrations. an intramolecular hydrogen bond was observed and indicating that thehydrazone forms is mostly predominant. the peak of the hydrazone proton was severelybroadened and its chemical shift appeared at down field ...

We have obtained the 13CR chemical shift tensors for each amino acid in the protein GB1. We then developed a CST force field and incorporated this into the Xplor-NIH structure determination program. GB1 structures obtained by using CST restraints had improved precision over those obtained in the absence of CST restraints and were also more accurate. When combined with isotropic chemical shifts,...

A novel method of chemical shift imaging utilizing echoplanar imaging (EPI) has been developed for the purpose of improving the spatial resolution of metabolite images for the specific goal of high spatial resolution mapping of neuronal content. An EPI sequence was modified to allow temporal offsets of the 180 degree refocusing pulse that encode the chemical shift information into the phase of ...

Silane-modified amphiphilic chitosan was synthesized by anchoring a silane coupling agent, (3-aminopropyl)triethoxysilane, to a novel amphiphilic carboxymethyl-hexanoyl chitosan (CHC). The chemical structure of this new organic-inorganic hybrid molecule was characterized by FTIR and 13C-, 29Si-nuclear magnetic resonance, while the structural evolution was examined using scanning electron micros...

Several inconsistencies have been noted during recent systematic studies of the validity of additivity relationships (1-6) in the C chemical shifts of substituted pyridines. These showed that substantial errors could be introduced if care is not taken to use, for a given solvent, approximately the same concentration for all solutes; in our case this applied to monosubstituted and polysubstitute...

A two-step acid-base-catalyzed silica gel has been aged in a series of alcohol and water baths and some chemical and physical structures of the gel were measured using several techniques (low-field NMR, 29Si and 13C MAS-NMR, IR, Raman, nitrogen adsorption) on gels in wet and dry states. When the gel was placed in alcohol, the surface area increased as a result of esterification and depolymeriza...