Backbone conformational change in the A to B Transition of deoxyribonucleic acid.

Infrared linear dichroism studies of A-and B-DNA films reveal six 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 to B transition, according to models derived from x-ray work.