A Crystal Structure of an Oligoproline Hexamer with a Zig-zag Arrangement

Abstract

Oligoprolines adopt the well-defined polyproline II (PPII) helical conformation, even at a short chain length of six residues. These rigid peptides are versatile molecular rulers and scaffolds, yet there has been great difficulty in obtaining single crystals for X-ray crystal structure analysis to probe their conformation in the solid state. Here, we report a crystal structure of an oligoproline hexamer bearing an N-terminal terephthalic acid moiety. Comparison with that of a previously obtained crystal structure of a closely related hexaproline revealed influence of the terminal functional groups and the solvent on the crystal packing.