LOCAL RAMAN TENSORS OF CYTIDINE AND THEIR ORIENTATIONS IN POLY(RI)CENTER-DOT-POLY(RC)

Polarized Raman spectra of a cytidine single crystal have been observe d with 488.0 nm excitation by use of a Raman microscope. For each Rama n band, the relative intensities of aa, bb, cc, ab and be tensor compo nents have been determined. The depolarization ratios were also determ ined in a cytidine solution. The shape and orientation of the local Ra man tensor were deduced for each prominent Raman band, i.e. its princi pal axes and relative magnitudes of its components (r(1) = alpha(xx)/a lpha(zz), r(2) = alpha(yy)/alpha(zz)). The tensor for a strong Raman b and at 1254 cm(-1) was assumed to have the principal x axis along the NI-C4 line, the y axis along the N3-C5 line, and r(1) = 13.2, r(2) = - 6.1. The tensor of the 793 cm(-1) band was assumed to have a similar a xis system, and r(1) = 3.8, r(2) = 3.2. The tensor of the anisotropic band at 603 cm(-1) was assumed to have the principal x axis along the C2-N1 line, the y axis along the C2-C4 line, and r(1) = -0.2, r(2) = 2 0 Such information about the cytidine tensors is useful in determining the orientation of this residue in a biological fiber. As an example, a poly(rI) . poly(rC) duplex fiber has been subjected to an examinati on.