Regularly alternating L,D-peptides. I. The double-stranded left-handed antiparallel β-helix in the structure of Boc-(L-Val-D-Val)4-OMe
✍ Scribed by Benedetto Di Blasio; Ettore Benedetti; Vincenzo Pavone; Carlo Pedone; Ottavia Spiniello; Gian Paolo Lorenzi
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1989
- Tongue
- English
- Weight
- 449 KB
- Volume
- 28
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
The structure of Boc-(L-Val-D-Val),-OMe has been determined by x-ray single-crystal diffraction analysis. The octapepti+ crystallizes in the trigonal system, space group P3,21 with a = b = 12.760 A, c = 63.190 A and Z = 6. The independent unit is represented by one octapeptide chain. The structure has been solved by direct methods and it was anisotropically refined by least-squares procedures to a h a l R value of 0.08 for the 3018 "observed" reflections. One molecule of water was also located in the unit cell. Two octapeptide chains, related by a crystallographic binary axis, wind up around each other giving rise to a double-stranded lefthanded antiparallel t.l /35.6-helix. The h e r , stabilized by 14 interstrand N-H--O=C hydrogen bonds, can be regarded as a cylinder with an hydrophilic inner core represented by the peptid? units and an hydrophobic exterior of isopropyl groups. The inner diameter of the cylinder is 5.1 A.