Dependence of B-A Conformational Change in DNA on Base Composition

IT is generally accepted that all native DNAs, irrespective of their origin, give essentially identical X-ray diffraction patterns characteristic of the A form at high humidities and of the A form at lower humidities^{1, 2}. The purpose of the work described here was an accurate characterization of B-A conformational changes in a range of DNA by infrared dichroism, which seems to be particularly appropriate for the structural characterization of nucleic acids^3–6 as a complement of X-ray diffraction. In previous infrared studies the A form and B-A conformational changes were not observed⁷.