An infrared study of the influence of growth media and myo-inositol on structural changes in DNA induced by dehydration and ultraviolet light

Abstract

The infrared spectra of films of deoxyribonucleic acid (DNA), ribonucleic acid (RNA), and synthetic polynucleotides have been studied under varying degrees of relative humidity (R.H.) in the presence and absence of myo-inositol. In addition the effect of 2537 Å light (ultraviolet) on the hydration of DNA has been investigated. As other researchers have shown, when the R.H. is lowered shifts in the P=O and C=O absorption frequencies occur. These shifts seem to be associated with the removal of approximately 12 molecules of water/nucleotide and all are prevented by the presence of 2 molecules of inositol/nucleotide during desiccation. The irradiation of DNA at 75% R.H. with ultraviolet also produces spectral shifts which appear to arise as a result of bound water molecules moving from P=O and C=O groups.The response of bacterial DNA to desiccation appears to depend on the medium in which the cells are grown. The DNA from cells grown in a minimal salts medium is less hydrated at a given R.H. level than the DNA from cells grown in an enriched medium. This loss of water-adsorbing sites is considered to be due to a physiological replacement of water on the DNA of cells grown on minimal salt medium by amino acids or proteins. RNA and polynucleotides are less hydrated than DNA, which is assumed to be due to their lack of an ordered double helical structure. Of the synthetic polynucleotides poly-I was found to most closely resemble the behavior of DNA. The ability of inositol to prevent spectral shifts in DNA caused by desiccation and irradiation tends to substantiate the suggestion that it preserves the biological integrity of cells and viruses during stress by combining with DNA.