Structure of N-acetyl-D-alanyl-D-alanine hydrate. An analogue of the COOH-terminal segment of peptidoglycan of bacterial cell walls.
The solid state conformational analysis of Ac-D-Ala-D-Ala-OH.H2O, carried out by infrared absorption and X-ray diffraction, has indicated that the molecules are not extended in a regular beta conformation, but rather that they are partially folded, the phi, psi torsional angles of the COOH-terminal residue in particular being in the region of the left-handed alpha helix of the Ramachandran map. The acetylamino and peptide groups ar found in the usual trans conformation, the latter, however, exhibiting a deviation from rigid planarity. Only intermolecular hydrogen bonds occur in the crystal state. The solution conformational analysis, performed by infrared absorption and CD, has revealed that the amount of intramolecular N--H ... O==C hydrogen-bonded folded forms, if any, should be extremely small, even in deuteriochloroform at high dilution. In water, solvated, unordered species largely predominate.
D001419:Bacteria / Q000032:analysis; D002236:Carbohydrate Conformation; D002473:Cell Wall / Q000032:analysis; D002942:Circular Dichroism; D004151:Dipeptides; D010457:Peptidoglycan; D013055:Spectrophotometry, Infrared; D013329:Structure-Activity Relationship; D014961:X-Ray Diffraction
D004151:Dipeptides; D010457:Peptidoglycan; C031735:acetylalanylalanine