INFRARED CD OF DEOXY OLIGONUCLEOTIDES - CONFORMATIONAL STUDIES OF 5'D(GCGC)3', 5'D(CGCG)3', 5'D(CCGG)3', AND 5'D(GGCC)3' IN LOW AND HIGH-SALT AQUEOUS-SOLUTION

Infrared (vibrational) circular dichroism (VCD) spectra have been obtained for the self-complementary tetranucleotides, 5d(CGCG)3', 5'd(GCGC)3', 5'd(CCGG)3', and 5'd(GGCC)3'. In buffered aqueous solution at low salt concentration, these tetramers exhibit spectra associated with right-handed polymers, although the spectra differ significantly for the four species. In high salt solution, a B --> Z transition occurs in 5'd(CGCG(3', while the other tetranucleotides appear only slightly altered. Temperature dependent studies of these oligonucleotides reveal a greater amount of thermal stability for the tetramers in low salt than for the high salt solutions. VCD intensities computed via the exciton formalism are compared with observed results.