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Stereochemical studies on cyclic peptides. XIII. Energy minimization studies on cyclic hexapeptides having hydrogen bonds

Paul, PKC and Ramakrishnan, C (1987) Stereochemical studies on cyclic peptides. XIII. Energy minimization studies on cyclic hexapeptides having hydrogen bonds. In: International Journal of Peptide & Protein Research, 29 (4). pp. 433-454.

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Abstract

The basic cyclic hexapeptide conformation which accommodate hydrogen bonded and turns in the backbone have been worked out using stereochem. criteria and energy minimization procedures. Cyclic hexapeptides can be made up of all possible combinations of 4:1 hydrogen bonded types I, I', II and II' turns, giving rise to sym. conformations having two-fold and inversion symmetries as well as nonsym. structures. Conformations having exclusive features of 3:1 hydrogen bonded turns were found to be possible in threefold and S6 sym. cyclic hexapeptides. The cyclic hexapeptides formed by the linking of two turn tripeptide fragments differ mainly in the hydrogen bonding scheme present in the turn tripeptides and the conformation at the -carbon atoms where the two tripeptide fragments link. The different hydrogen bonding schemes found in the component turns are: 1) a turn with only a 4 : 1 hydrogen bond, 2) a type I or I' turn with 4 : 1 and 3 : 1 hydrogen bonds occurring in a bifurcated form and 3) a type II or II' turn having both the 4 : 1 and the 3 : 1 hydrogen bonds with the same acceptor oxygen atom. The conformation at the linking -carbon atoms lie either in the extended region or in the 3 : 1 hydrogen bonded turn or inverse turn regions. Further, the threefold and the S6 sym. conformations have three turns interleaved by three extended regions or three inverse turns, resp. The feasibility of accommodating alanyl residues of both isomeric forms in the CHP min. has been explored. The available exptl. data are reviewed in the light of the present results.

Item Type: Journal Article
Additional Information: Copyright belongs to Copenhagen : Munksgaard
Department/Centre: Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited: 31 Mar 2008
Last Modified: 27 Aug 2008 13:16
URI: http://eprints.iisc.ernet.in/id/eprint/13439

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