Abstract
Double labeling and the isolation of peptides specific to muscle actin indicates that completely homologous 20-residue peptides can be produced from the C-terminal regions of muscle and chicken-embryo fibroblast actins by treatment with CNBr. By quantification of the amount of this peptide that can be produced from acetone-dried powders by CNBr treatment, 6.8% of the protein of the fibroblasts was estimated to be actin.