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 obta ined 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 r ight-handed polymers, although the spectra differ significantly for th e four species. In high salt solution, a B --> Z transition occurs in 5'd(CGCG(3', while the other tetranucleotides appear only slightly alt ered. Temperature dependent studies of these oligonucleotides reveal a greater amount of thermal stability for the tetramers in low salt tha n for the high salt solutions. VCD intensities computed via the excito n formalism are compared with observed results.