Infrared Studies on the Backbone Conformation of Nucleic Acids

Abstract

Abstract The presence and assignment of low frequency infrared bands characteristic of the A, B and C forms of DNA (Salmon Sperm and Micrococcus Lysodeikticus) and of synthetic poly (dA‐T): (dA‐T) and of polyribonucleotides‐A form are considered. The vibrational modes that may arise from the phosphate diester stretch of DNA backbone are investigated in the region of 750 cm −1 –900 cm −1 . The proposed assignment of the IR bands occurring at about 837 cm −1 to the vibrations of the phosphate diester C–O–P–O–C chain in a specific conformation allow characterization of the backbone geometry in the B and C forms. The bands situated at 812 cm −1 and 860 cm −1 are undoubtedly characteristic of the backbone phosphodiester chain of the A form. The possibility of other contributions to the 812 cm −1 band is also discussed.