On the specificity of caffeine effects

Summary Caffeine in 0.1% or higher concentration reversibly inhibits E. coli and yeast growth. It inhibits RNA and protein synthesis (Tables 1+3) within a few minutes after being added to the incubation medium (Fig. 2). The suggestion is made that these effects of caffeine, as well as its synergism with some mutagens, are due to its ability to costack with free purines and to form complexes with single-stranded nucleic acids.