Two different forms of aggregated dimers of ribonuclease A

Results of gel filtration experiments performed with two different chromatographic media (Superose 12 HR 10/30 and Superdex 75 HR 10/30) and of polyacrylamide gel electrophoresis under non-denaturing and denaturing conditions suggest that aggregated dimers of bovine RNase A, obtained by lyophilization of the enzyme from 40% acetic acid solutions (5 mg RNase A per ml), might consist of two differently structured forms. These two species have slightly different retention times in gel-filtration experiments and migrate differently in electrophoresis under non-denaturing conditions. The fast migrating dimer in non-denaturing gel electrophoresis is able to degrade double-stranded poly(A).poly(U) more efficiently than the other, and the two forms are found in a ratio of about 3:1.