A DOQSY approach for the elucidation of torsion angle distributions in biopolymers: application to silk.
Silk from the wild silkworm Samia cynthia ricini with a molecular mass of about 300kDa consists of alternating repeats of nano-crystalline poly-(Ala) and non-crystalline glycine-rich domains. The backbone torsion angles between pairs of these two amino acids is determined by DOQSY solid-state NMR spectroscopy: the alanine-rich domains are predominantly in a beta-sheet conformation, whereas the glycine-rich domains are found to be partially in an extended beta-sheet conformation and partially in an approximately 3(1)-helical conformation. In the cast film from liquid silk significantly different secondary structures were found: the alanine-rich domains are alpha-helical conformation, whereas the results for glycine-labelled sample are explained by a random-coil state. A detailed error analysis of the technique is presented.
van Beek
Jacco D
JD
Physical Chemistry, ETH Zurich, CH-8093 Zurich, Switzerland.
Meier
Beat H
BH
D000409:Alanine / Q000737:chemistry; D000818:Animals; D005998:Glycine / Q000737:chemistry; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D011487:Protein Conformation; D047011:Silk / Q000737:chemistry*
D047011:Silk; D000409:Alanine; D005998:Glycine