Reversible temperature dependent spectral shift in the infrared spectrum of DNA (Na) in the dry solid state

Abstract

The unpolarised 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 –45°C and + 95°C. 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 are 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.