Single methyl groups can act as toggle switches to specify transmembrane protein-protein interactions These results highlight the high intrinsic specificity of TMD interactions, demonstrate that a single methyl group can dictate specificity, and define the minimal chemical difference that can modulate the specificity of TMD interactions and the activity of transmembrane proteins. RNA-directed DNA methylation is energy-dependent. The “minimal chemical difference” is linked from the quantized energy of virucidal light to all biophysically constrained biodiversity via base pair changes, single…