ISSN:
0006-3525
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The conformations of a pentapeptide L-His-L-Arg-L-Trp-Gly with weak adrenocorticotropin (ACTH) activity and its analogs, where each L-amino acid residue is substituted by D-residue, were investigated by means of proton and carbon-13 nmr spectroscopy on their DMSO-d6 solutions. The spectra indicated the presence of slowly exchangeable conformation isomers for D-Phe and D-Arg analogs, due to steric hindrance around the arginine residue. The activation energy of the hindered rotation of the arginine side chain was estimated to be more than 19 ∼ 20 kcal/mol. Spin-lattice relaxation times of carbon-13 nuclei also indicated slow segmental motion of the arginine side chain of the D analogs. An effect on proton chemical shifts by intermolecular electrostatic interaction between the arginine side chain and the C terminal carboxylic residue was observed. We did not observe, however, a direct correlation between pentapeptide activity and molecular conformation at this stage of the experiments.
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bip.1981.360201013
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