ISSN:
0006-3525
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The 13C chemical shifts and spin-lattice relaxation times are reported for cyclo(L-Pro-L-Leu) and cyclo(L-Pro-D-Leu). The chemical shifts of the D and L leucyl residues in the cyclic peptides differ from each other by 1.8 and 3.6 parts per million for the α and β carbons, respectively. The α-carbons of the prolyl residues differ by 1.0 ppm as a consequence of proximity to a D or an L leucyl residue. The 13C spin-lattic relaxation time(T1) of the prolyl residues, but not the leucyl residues, in both compounds are indicative of difference in conformational equilibria within the pyrrolidine ring in the L-L isomer as compared to the L-D isomer. Anisotropic overall molecular reorientation is not responsible for the differences observed in the T1 values. The differences in T1 values and chemical shifts between cyclo(L-Pro-L-Leu) and cyclo(L-Pro-D-Leu) appear to result from a difference in conformations of the two diketopiperazine rings.
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bip.1976.360150905
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