Ethanol extraction requirement for purification of protein labeled with [h]leucine in aquatic bacterial production studies

The trichloroacetic acid (TCA)-insoluble fraction of water column bacteria labeled with [H]leucine contained an ethanol-soluble fraction accounting for up to 44% of the label. A component of the ethanol-soluble fraction is [H]leucine. Labeled-protein purification requires an ethanol wash step. Cold TCA can replace hot TCA for precipitation of labeled proteins.