1.Effects of thioamide substitution for the enkephalin conformation. Crystal structure of Boc-Tyr-Gly-Gly-Phe psi [CSNH]Leu-OBzl.
Doi M1, Takehara S, Ishida T, Inoue M. Int J Pept Protein Res. 1989 Nov;34(5):369-73.
The crystals of Boc-Tyr-Gly-Gly-Phe psi[CSNH]Leu-OBzl monohydrate (C40H51N5O8S.H2O), a monothionated Leu-enkephalin analogue, were obtained with space group P2(1), a = 12.616(3), b = 9.347(2), c = 18.548(5) A, beta = 96.31(4) degrees. The structure was elucidated by X-ray diffraction analysis, and refined to the R value of 0.091 for the observed 3294 reflections. Two antiparallel molecules related by a pseudo twofold symmetry were stabilized to each other by four intermolecular hydrogen bonds. The molecular conformation was bent at the Phe residue, and the extended moiety of the Tyr-Gly-Gly fragment was almost perpendicular to that of the Phe-Leu residues. Consequently the molecule, as a whole, formed an L-shape conformation with a slightly left-handed helicity.
