Conformational Analysis of the Biologically Active Cyclic Analog of beta-Casomorphin H-Tyr-cyclo[D-OrnPheProGly]

P. V. Kostetsky^* and S. F. Arkhipova

Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, ul. Miklukho-Maklaya 16/10, Moscow, 117871 Russia; E-mail: pkos@ibch.siobc.ras.ru

^* To whom correspondence should be addressed.

Received December 9, 1998; Revision received April 29, 1999

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A biologically active analog of beta-casomorphin, H-Tyr-cyclo[D-OrnPheProGly], was studied by theoretical conformational analysis. Random sampling was used to search the conformational space of allowed dihedral angles. Among 53 low-energy conformers with different folding of the peptide cyclic moiety, only those were selected which correspond to the low-energy area of the model linear tripeptide Ac-D-AlaAlaPro-NHMe. This peptide was used as the main chain "template" for the D-OrnPheProGly fragment of the studied cyclopeptide molecule. Only 15 conformers were chosen as potentially biologically active structures. The conformational possibilities of the Phe residue were constrained to the combined (A + G) region of the Ala residue phi,psi-map for linear peptides.

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KEY WORDS: cyclopeptide, theoretical conformational analysis, beta-casomorphin

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