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Biophys J. 2007 Dec 15;93(12):4433-44. Epub 2007 Aug 31.

Sum frequency vibrational spectroscopy: the molecular origins of the optical second-order nonlinearity of collagen.

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  • 1Department of Electrical and Computer Engineering, University of California, Davis, California, USA.

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.

PMID:
17766339
[PubMed - indexed for MEDLINE]
PMCID:
PMC2098726
Free PMC Article
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