ISSN:
0006-3525
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Biscyclo(Cys-Sar) [I] and biscyclo(Cys-Pro) [II] were prepared by the extension of amino acid moieties from cystine. Compound I equilibrates between two rotamers around the CSSC bond of the cystine residue in methanol, showing dual negative CD transitions (CS-SC) at 270 and 255 nm, and dual S-S vibrations at 507 and 539 cm-1 in Raman spectra. In contrast, a conformation of P-helix type is suggested in CH3CN, which shows a distinct negative CD at 270 nm and only one Raman band at 507 cm-1 for the S-S bond. Compound II rotates freely in dimethylsulfoxide (Me2SO) but takes a relatively stable conformer of P-helix type in methanol, chloroform/Me2SO (9:1), and chloroform/trifluoroacetic acid (9:1). The conformation in chloroform is retained even on addition of trifluoroacetic acid. A more complete conformation of compound II in water was determined from the negative CD of S-S transition and 1H-nmr spectra of the Cys-β-CH2 protons.
Additional Material:
9 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bip.1981.360201202
Permalink