Official websites use .gov A .gov website belongs to an official government organization in the United States.
Secure .gov websites use HTTPS A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.
Caption by Maclyn McCarty reads: "Titration of the last preparation of purified DNA from pneumococcus type III before beginning the process of preparing the paper for publication. All procedures in the purification process had been carried out in the cold, except for treatment with ribonuclease and the Dubos enzyme hydrolyzing the capsular polysaccharide. This preparation showed transforming activity in 50% of the tubes containing 0.003 micrograms of the final product."