Open AccessEffect of pressure on the crystal structure of α‐glycylglycine to 4.7 GPa; application of Hirshfeld surfaces to analyse contacts on increasing pressure
Author(s) -
Moggach Stephen A.,
Allan David R.,
Sawyer Lindsay,
Parsons Simon
Publication year - 2006
Publication title -
acta crystallographica section b
Language(s) - English
Resource type - Journals
eISSN - 1600-5740
pISSN - 0108-7681
DOI - 10.1107/s0108768105042072
Subject(s) - glycylglycine , crystallography , hydrogen bond , antiparallel (mathematics) , chemistry , crystal structure , covalent bond , beta sheet , molecule , chemical physics , protein structure , organic chemistry , physics , glycine , biochemistry , amino acid , quantum mechanics , magnetic field
The crystal structure of α‐glycylglycine (α‐GLYGLY) has been determined at room temperature at pressures between 1.4 and 4.7 GPa. The structure can be considered to consist of layers. The arrangement of molecules within each layer resembles the antiparallel β‐sheet motif observed in proteins, except that in α‐GLYGLY the motif is constructed through NH⋯O hydrogen bonds rather than covalent amide links. Compression of α‐GLYGLY proceeds via the reduction in void sizes. Voids close in such a way as to decrease the distances of stabilizing interactions such as hydrogen bonds and dipolar contacts. The largest reductions in interaction distances tend to occur for those contacts which are longest at ambient pressure. These longer interactions are formed between the β‐sheet‐like layers, and the largest component of the strain tensor lies in the same direction. The N⋯O distance in one NH⋯O hydrogen bond measures 2.624 (9) Å at 4.7 GPa. This is very short for this kind of interaction and the crystal begins to break up above 5.4 GPa, presumably as the result of a phase transition. The changes that occur have been analysed using Hirshfeld surfaces. Changes in the appearance of these surfaces enable rapid assessment of the structural changes that occur on compression.