Crystal structure and conformation of the cyclic tetramer of a repeat tripeptide of elastin, cyclo(l‐valyl‐l‐prolylglycyl)4

Abstract
X-ray diffraction data were used to determine the crystal structure of cyclo-(L-Val-L-Pro-Gly)4, the cyclic tetramer of a repeat tripeptide of elastin. The crystals are monoclinic, space group C2, with a = 29.639(3), b = 7.099(1), c = 20.325 (2) .ANG., and .beta. = 130.4(4).degree.. The structure was solved by direct methods and refined by least squares to R = 0.082 for 2603 observed reflections. The cyclic dodecapeptide contains 2 .beta.(II) turns. Hydrophilic and hydrophobic channels that run parallel to the b axis are formed by the stacking of cyclic peptides on 2-fold axes.