Reversible Temperature Dependent Spectral Shift in the Infrared Spectrum of DNA (Na) in the Dry Solid State

Abstract

The unpolariscd infrared spectrum of freeze-dried layers of calf thymus DNA(Na) has been recorded over the range from 4000 cm-1 to 625 cm-1 at temperatures between — 45CC and + 95CC. Throughout the temperature variations, the samples were maintained in a very dry state. The position of the absorption band at approximately 1230 cm-1 is shown to depend on temperature and to be capable of a reversible shift over a range of ~16 cm-1. The results arc compared with previously published low-frequency dielectric measurements on similar samples and with polarised infrared measurements showing the influence of changes in relative humidity on the structure of DNA salts.