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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
Author(s) -
Di Blasio Benedetto,
Benedetti Ettore,
Pavone Vincenzo,
Pedone Carlo,
Spiniello Ottavia,
Lorenzi Gian Paolo
Publication year - 1989
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360280121
Subject(s) - antiparallel (mathematics) , chemistry , crystallography , dimer , helix (gastropod) , molecule , stereochemistry , crystal structure , hydrogen bond , monoclinic crystal system , physics , ecology , organic chemistry , quantum mechanics , snail , magnetic field , biology
The structure of Boc‐( L ‐Val‐ D ‐Val) 4 ‐OMe has been determined by x‐ray single‐crystal diffraction analysis. The octapeptide crystallizes in the trigonal system, space group P3 2 21 with a = b = 12.760 Å, c = 63.190 Å 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 final 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 left‐handed antiparallel ↑↓ β 5.6 ‐helix. The dimer, stabilized by 14 interstrand NH ⃛OC hydrogen bonds, can be regarded as a cylinder with an hydrophilic inner core represented by the peptide units and an hydrophobic exterior of isopropyl groups. The inner diameter of the cylinder is 5.1 Å.