A THYROTROPIN-RELEASING-HORMONE ANALOG - PGLU-PHE-D-PRO-PSI[CN4]-NME AT 293 AND 107 K

Data have been measured at two temperatures, 293 K and 107 K, for a cr ystal of a thyrotropin-releasing hormone analogue, pGlu-Phe-D-Pro-Psi [CN4]-NMe, C20H25N7O3, and the structures solved and refined. The trip eptide contains a tetrazole ring which mimics a cis-peptide bond at th e C terminus. An intermolecular hydrogen bond exists between two molec ules related by the twofold screw axis, resulting in infinite chains o f hydrogen-bonded peptide molecules. Because of the folding and packin g of the molecules, there are no intermolecular contacts of less than 4 Angstrom to the N atom of the phenylalanine residue.