RAMAN-SCATTERING TENSORS OF TYROSINE

Polarized Raman scattering measurements have been made of a single cry stal of L-tyrosine by the use of a Raman microscope with the 488.0-nm exciting beam from an argon ion laser. The L-tyrosine crystal belongs to the space group P2(1)2(1)2(1) (orthorhombic), and Raman scattering intensities corresponding to the aa, bb, cc, ab and ac components of t he crystal Raman tensor have been determined for each prominent Raman band. A similar set of measurements has been made of L-tyrosine-d(4), in which four hydrogen atoms on the benzene ring are replaced by deute rium atoms. The effects of NH3 --> ND3 and OH --> OD on the Raman spec trum have also been examined. In addition, depolarization ratios of so me bands of L-tyrosine in aqueous solutions of pH 13 and pH 1 were exa mined. For comparison with these experimental results, on the other ha nd, ab initio molecular orbital calculations have been made of the nor mal modes of vibration and their associated polarizability oscillation s of the L-tyrosine molecule. On the basis of these experimental data and by referring to the results of the calculations, discussions have been presented on the Raman tensors associated to some Raman bands, in cluding those at 829 cm(-1) (benzene ring breathing), 642 cm(-1) (benz ene ring deformation), and 432 cm(-1) (C alpha-C beta-C gamma bending) . (C) 1998 John Wiley & Sons, Inc.