L-Alanyl-L-alanyl-L-alanine: Parallel pleated sheet arrangement in unhydrated crystal structure, and comparisons with the antiparallel sheet structure
✍ Scribed by A. Hempel; N. Camerman; A. Camerman
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1991
- Tongue
- English
- Weight
- 393 KB
- Volume
- 31
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
The tripeptide L-alanyl-L-alanyl-L-alanine has been crystallized from a water/dimethylformamide solution in an unhydrated form, with cell dimensions a = 11.849, b = 10.004, c = 9.862 A, p = 101.30", monoclinic space group P21, with 4 molecules per cell ( 2 independent molecules in the asymmetric unit). The structure was determined by direct methods and refined to a discrepancy index R = 0.057. The tri-L-alanine molecules are packed in a parallel pleated sheet arrangement with unusually long amide nitrogen-carbonyl oxygen contacts within sheets. Comparisons are made with the antiparallel pleated sheet structure of tri-L-alanine hemihydrate, previously crystallized from the same solvent system.
' B e q = 4 / 3 ( B ( 1 , 1)a' + R ( 2 , 2 ) b 2 + B ( 3 , 3)c' + R ( 1 , 2)ab cos y + R(1, 3 ) a c cos 0 + B ( 2 , 3)bc cos a ) .