The crystal structure of N-acetyl-L-prolyl-D-alanyl-methylamide hemi hydrate by the method of packing analysis on contact criteria

Abstract

The structure determination of the tripeptide N-acelyl-L-prolyi-D-alanyl-methylamide by the method of packing analysis is described. The molecular geometry deduced from conformational analysis as used to orient and position the molecules in the Unit cell and various trial crystal structures were generated and refined against the X-ray data in a systematic way. Out of the eight reasonable packing arrangements, one refined to an R-value of 0-30 by me rigid body refinement procedure, when 50 low-angle reflections were used. This model was further refined by a series of conventional leastsquare procedures gradually increasing the number of reflections at each stage to a final R value of 0·062.