RNA absorbances in modified cellulose disks.

Bichromatic spectrophotometry determinations were performed on Whatman chromatographic paper disks impregnated with rRNA solutions of different concentrations, at ionic strengths ranging from nearly 0 to 1.4 M. The disks consisted of cellulose, either native or modified (by grafting of carboxymethyl, phosphate, Ecteola or DEAE groups, or by loading with silica gel). The results demonstrate that: 1) there is a positive correlation between the absorbance enhancement by multiple light scattering and the nearness of the nucleic acid molecules in relation to the surface of cellulose fibrils; b) the action on absorbance of ionic strength and of other physical factors differs in terms of the electric charges and of the exposure of other groups that may interact with nucleic acids through hydrogen bonds or Van der Waals forces.