Structural and conformational properties of (Z)-beta-(1-naphthyl)- dehydroalanine residue.
To understand how chemical structure of beta-substituted alpha, beta-dehydroalanine (particularly size and pi conjugation of beta substituent) affects conformational property, x-ray crystallographic analysis was performed on Boc-Ala-Delta(Z) Nap-Val-OMe [Boc: t-butoxycarbonyl; Delta(Z) Nap: (Z)-beta-(1-naphthyl)dehydroalanine; OMe: methoxy] having the naphthyl group as a bulky beta substituent. Single crystals were grown by slow evaporation from an ethanol solution in the triclinic space group P1 with a = 9.528 (3) A, b = 12.410(4) A, c = 5.975(2) A, alpha = 96.77(3) degrees, beta = 102. 81(2) degrees, gamma = 88.74(3) degrees, V = 684.1(4) A3, and Z = 1. Phase determination was carried out by a direct method (SHELEXS), and the final structure was refined to R = 8.1% and R(w) = 9.0% for 1964 observed reflections. The bond lengths and bond angles of the Delta(Z)Nap residue, characterized by a sp(2) hybridized C(alpha) atom, did not differ from those of other dehydroresidues such as Delta(Z) Phe, Delta(Z) Leu, and DeltaVal essentially. The peptide backbone took a type II beta-turn conformation involving an intramolecular hydrogen bond between CO(Boc) and NH(Val), similar to di- or tripeptides containing a Delta(Z) Phe or Delta(Z) Leu residue in the second positions. Here the naphthyl group was found to be nonplanar [chi(2) = 55(1) degrees ] relative to the C(alpha)==C(beta)==C(gamma) plane. The nonplanarity was supported by conformational energy calculation. The molecular packing was stabilized by two kinds of intermolecular hydrogen bonds and van der Waals interactions. Naphthyl groups were arranged in a partially overlapped face-to-face orientation with a center-to-center distance of 5.97 A. For additional information, peptide Boc-(Ala-Delta(Z) Nap-Leu)(2)-OMe was synthesized and its solution conformation was investigated by (1)H-NMR spectroscopy. The hexapeptide showed the tendency to form a 3(10)-helical conformation in solution essentially. Conformational properties of Delta(Z) Nap residue, characterized by a type II beta-turn and 3(10)-helix, were supported by a conformational energy contour map of the Delta(Z)Nap residue.
Inai
Y
Y
Department of Environmental Technology and Urban Planning, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan.
Oshikawa
T
T
Yamashita
M
M
Hirabayashi
T
T
Hirako
T
T
D000409:Alanine / Q000031:analogs & derivatives* / Q000737:chemistry; D018360:Crystallography, X-Ray / Q000379:methods; D004151:Dipeptides / Q000138:chemical synthesis / Q000737:chemistry*; D007202:Indicators and Reagents; D008958:Models, Molecular; D008968:Molecular Conformation; D009842:Oligopeptides / Q000138:chemical synthesis / Q000737:chemistry*; D011487:Protein Conformation; D013329:Structure-Activity Relationship
D004151:Dipeptides; D007202:Indicators and Reagents; D009842:Oligopeptides; C419065:tert-butyloxycarbonylalanyl-naphthyldehydroalanyl-valyl-methyl ester; C015102:dehydroalanine; D000409:Alanine