Backbone conformational change in the A → B transition of deoxyribonucleic acid

Abstract

IR linear dichroism studies of A- and B-[calf thymus]DNA films reveal 6 bands between 2800 and 3000 cm-1 which must arise from deoxyribose and thymine methyl CH stretching motions. The band at 2890 is perpendicularly polarized in A-DNA but parallel polarized in B-DNA. This band most probably originates in the C''(5)H2 symmetric stretch; the polarization flip is consistent with the structural change occurring at C''(5) during the A .fwdarw. B transition, according to models derived from X-ray work.