RAMAN-SCATTERING TENSORS OF THYMIDINE

Polarized Raman scattering measurements have been made of a single cry stal of thymidine by use of a Raman microscope with 488.0 nm excitatio n. The crystal belongs to the space group P2(1)2(1)2(1) (orthorhombic) and the Raman scattering intensities of I-aa, I-bb, I-cc, I-bc, I-ca and I-ab, which correspond to the aa, bb, cc, be, cn and nb components , respectively, of the crystal Raman tensor, have been determined for each Raman band. The depolarization ratios of the Raman bands of this nucleoside have also been measured for fully random molecular orientat ion in an aqueous solution. A single crystal of thymidine-C-13(5) in w hich Ave carbon atoms of the deoxyribose moiety are uniformly substitu ted with C-13 atoms was also prepared and subjected to examinations si milar to those for the normal thymidine crystal. From these experiment al data, and by taking the known crystal structure into account, molec ular Raman tensors have been determined for the 1665, 1642, 1365, 1235 , 771 and 494 cm(-1) bands assignable to the thymine moiety, and for t he 898, 852 and 736 cm(-1) bands assignable to the deoxyribose moiety. This information about Raman tensors is considered to be useful for d etermining the orientations of thymidine residues in a biological comp lex from polarized Raman scattering measurements of such a complex. (C ) 1997 Elsevier Science B.V.