Studies of specificity of deoxyribonuclease from salmon testes

A limited digest of thymus DNA with salmon testes DNase was composed of fragments larger than tetranucleotides. With exhaustive digestion mono-, di-, and trinucleotides were formed. At the (3') omega terminus G predominated, its frequency ranged from approximately 35 to 72% and increased with decreasing size of fragments. The error caused by the ribose-containing contaminants of DNA is significant, and should not be neglected in the evaluation of nucleoside frequency at the terminal positions of fragments.