Sum frequency vibrational spectroscopy: the molecular origins of the optical second-order nonlinearity of collagen.
The molecular origins of second-order nonlinear effects in type I collagen fibrils have been identified with sum-frequency generation vibrational spectroscopy. The dominant contributing molecular groups are: 1), the methylene groups associated with a Fermi resonance between the fundamental symmetric stretch and the bending overtone of methylene; and 2), the carbonyl and peptide groups associated with the amide I band. The noncentrosymmetrically aligned methylene groups are characterized by a distinctive tilt relative to the axis perpendicular to the main axis of the collagen fiber, a conformation producing a strong achiral contribution to the second-order nonlinear effect. In contrast, the stretching vibration of the carbonyl groups associated with the amide I band results in a strong chiral contribution to the optical second-order nonlinear effect. The length scale of these chiral effects ranges from the molecular to the supramolecular.
Rocha-Mendoza
Israel
I
Department of Electrical and Computer Engineering, University of California, Davis, California, USA.
Yankelevich
Diego R
DR
Wang
Mingshi
M
Reiser
Karen M
KM
Frank
Curt W
CW
Knoesen
André
A
D003094:Collagen / Q000737:chemistry* / Q000648:ultrastructure*; D003198:Computer Simulation; D008956:Models, Chemical; D008958:Models, Molecular; D017711:Nonlinear Dynamics; D055095:Optics and Photonics; D011487:Protein Conformation; D012031:Refractometry / Q000379:methods; D014732:Vibration
D003094:Collagen