 In 1946, in the wake of the Avery–MacLeod–McCarty experiment showing that DNA, not protein, had the power to transform bacteria from one type to another, Hotchkiss rejoined Avery's lab.His work on protein analysis helped answer Avery's critics who argued that the experiment was not sufficiently rigorous to rule out protein contamination (and thus the possibility that protein was the transforming factor).Hotchkiss found that virtually all the detected nitrogen in the purified DNA used in for the transformation experiments came from glycine, a breakdown product of the nucleotide base adenine, and estimated that undetected protein contamination was at most .02%, although he did not publish this result until 1952 (the year of the Hershey–Chase experiment).