Structural variations in the crystal structures of two homologous DL-Leu and delta-Leu containing peptides.
The similar conformations and interaction modes of Ac-DL-Leu-NMe2 and Ac-delta-Leu-NMe2 molecules in the solid state allow the comparison of their geometrical parameters. The most evident variations are essentially restricted to the alpha, beta-unsaturated side-chain which adopts the Z-disposition. The dimensions of the peptide backbone are much less sensitive to alpha, beta-unsaturation, with a small shortening by 0.04 A and 0.02 A of the N--C alpha and C alpha--C' bonds, respectively, and an increase by 6 degrees of the N--C alpha--C' bond angle. The ethylenic and amide groups in the delta-Leu derivative are far from coplanarity, and a significant electronic conjugation of the pi-orbital is likely to be rejected.
el-Masdouri
L
L
URA-CNRS-809, University of Nancy, France.
Aubrey
A
A
Boussard
G
G
Marraud
M
M
D003460:Crystallization; D006860:Hydrogen Bonding; D007930:Leucine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D015394:Molecular Structure; D010455:Peptides / Q000737:chemistry*; D011487:Protein Conformation; D014961:X-Ray Diffraction
D010455:Peptides; C079674:acetyl-N-dimethyl-alpha,beta-dehydroleucinamide; C079673:acetyl-N-dimethylleucinamide; D007930:Leucine