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Cystine peptides Antiparallel β-sheet conformation of the cyclic biscystine peptide [Boc-Cys-Ala-Cys-NHCH3]2

Karle, IL and Anderson, Flippen JL and Kishore, R and Balaram, P (1989) Cystine peptides Antiparallel β-sheet conformation of the cyclic biscystine peptide [Boc-Cys-Ala-Cys-NHCH3]2. In: International Journal of Peptide & Protein Research, 34 (1). pp. 37-41.

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The crystal structure analysis of the cyclic biscystine peptide [Boc-Cys1-Ala2-Cys3-NHCH3]2 with two disulfide bridges confirms the antiparallel ?-sheet conformation for the molecule as proposed for the conformation in solution. The molecule has exact twofold rotation symmetry. The 22-membered ring contains two transannular NH ? OC hydrogen bonds and two additional NH ? OC bonds are formed at both ends of the molecule between the terminal (CH3)3COCO and NHCH3 groups. The antiparallel peptide strands are distorted from a regularly pleated sheet, caused mainly by the L-Ala residue in which ?=� 155° and ?= 162°. In the disulfide bridge C? (1)-C? (1)-S(1)-(3')-C?(3')-C?(3'), S�S = 2.030 Å, angles C? SS = 107° and 105°, and the torsional angles are �49, �104, +99, �81, �61°, respectively. The biscystine peptide crystallizes in space group C2 with a = 14.555(2) Ã…, b = 10.854(2) Ã…, c = 16.512(2)Ã…, and ?= 101.34(1) with one-half formula unit of C30H52N8O10S4· 2(CH3)2SO per asymmetric unit. Least-squares refinement of 1375 reflections observed with |F| > 3?(F) yielded an R factor of 7.2%.

Item Type: Journal Article
Publication: International Journal of Peptide & Protein Research
Publisher: John Wiley & Sons
Additional Information: Copyright of this article belongs to John Wiley & Sons.
Keywords: crystal structure;disulfide bridges;torsional angles ;22-membered ring ;twisted ?-sheet
Department/Centre: Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited: 03 Jun 2010 09:51
Last Modified: 22 Sep 2010 05:06
URI: http://eprints.iisc.ac.in/id/eprint/27234

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