简介:The molecular origins of second-order nonlinear effects in type I collagen fibrils have been identified with sumfrequency
generation vibrational spectroscopy. The dominant contributing molecular groups are: 1), the meth简介:The molecular origins of second-order nonlinear effects in type I collagen fibrils have been identified with sumfrequency
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.详细>