research papers
A detailed analysis of the occurrence of the C—HO hydrogen bonds in sheet regions of proteins has been presented. 11 unique protein structures with resolution 1.3 Å containing β-sheets show a widespread presence of C—HO hydrogen bonds. These have average CαO, CHO distances and a Cα—HO angle of 3.29, 2.38 Å and 143°, respectively. As in the case of N—HO hydrogen bonds, parallel and antiparallel β-sheet regions show the same hydrogen-bond geometry. An inverse correlation is observed between the hydrogen-bond geometries involving the Cαi—HO=C and the Ni+1—HO=C suggesting that C—HO hydrogen bonds may act as an additional stabilizing factor. The propensity of different amino-acid residues to form such hydrogen bonds varies and shows a clear preference for valine and threonine. C—HO hydrogen bonds involving side chains also occur extensively in β-sheet regions.