title: Sum frequency vibrational spectroscopy: the molecular origins of the optical second-order nonlinearity of collagen.
abstract: 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.
authors.affiliation: Department of Electrical and Computer Engineering, University of California, Davis, California, USA.
authors.forename: Israel
authors.initials: I
authors.lastname: Rocha-Mendoza
authors.forename: Diego R
authors.initials: DR
authors.lastname: Yankelevich
authors.forename: Mingshi
authors.initials: M
authors.lastname: Wang
authors.forename: Karen M
authors.initials: KM
authors.lastname: Reiser
authors.forename: Curt W
authors.initials: CW
authors.lastname: Frank
authors.forename: André
authors.initials: A
authors.lastname: Knoesen
mesh_terms: 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
chemical_list: D003094:Collagen