Standard dimensions for cis N-methyl peptide unit and flexibility of cis peptide units

Ramnarayan, K. ; Ramakrishnan, C. (1987) Standard dimensions for cis N-methyl peptide unit and flexibility of cis peptide units Journal of Biosciences, 12 (4). pp. 331-347. ISSN 0250-5991

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The mean dimensions of the cis N-methyl peptide unit have been arrived at by analysing the crystal structure data on compounds containing such units. These dimensions can be used as standard in conformational studies on cyclic peptides. While the bonds meeting at C are almost coplanar, those meeting at N show a slight pyramidal disposition. A comparison of the dimensions of the normal and N-methylatedcis peptide units show that there are perceptible differences in the parameters connected with N. In addition, the flexibility of the cis peptide unit has been analysed by studying the distribution of the parameters in different classes of compounds such as cyclic di, tri and higher peptides. The salient features are: (i) The angle CαCN in cyclic dipeptide and the angle CδNCα in higher peptides tend to be lower, when the peptide unit is associated with a prolyl residue; (ii) in cyclic tripeptides the internal anglesviz., CαCN and CNCα are significantly larger thereby increasing the intra-annular space; (iii) the bond Cα-C is distinctly shorter when it occurs in cyclic dipeptides. The results lead to the conclusion that thecis peptide unit takes up a need-based flexibility in its dimension.

Item Type:Article
Source:Copyright of this article belongs to Indian Academy of Sciences.
Keywords:cis Peptide Units; Dimension of cis Peptide Unit; N-methylation in cis Peptide Unit; cis Peptide Units in Cyclic Peptides; Flexibility of cis Peptide Unit; Dimensions of N-methylatedcis Peptide Unit
ID Code:41017
Deposited On:26 May 2011 06:12
Last Modified:17 May 2016 22:53

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