Conformational changes induced in tobacco mosaic virus nucleic acid by ultraviolet radiation

Summary In order to study any Conformational changes associated with ultraviolet irradiation of TMV-RNA, methods of circular dichroism and absorbance-temperature profile were applied. RNA irradiated in water at 254 nm showed a distinct change in CD spectrum, but there was only a slight change accompanying irradiation in phosphate buffer.A small change in absorbance-temperature profile at 258 nm is associated with irradiation of RNA in water; RNA irradiated in phosphate buffer and Mg⁺⁺ solutions showed essentially no changes.It is concluded that conformational changes accompanying irradiation of RNA in water are greater than those taking place in phosphate or magnesium solutions, and the enhanced change in water is related to the larger quantum yield for inactivation found in water than in buffer solutions.Photochemistry of Macromolecules XXXIII, supported in part by the U.S. Atomic Energy Commission, contract AT(11-1)-34, Project 116.