– Myelin Basic Protein (MHP4-14) TFA, a synthetic peptide comprising residues 4-14 of myelin basic protein, serves as a highly selective substrate for protein kinase C (PKC) with a K_m of 7 μM. It is not phosphorylated by cyclic AMP-dependent protein kinase, casein kinases I and II, Ca^2+/calmodulin-dependent protein kinase II, or phosphorylase kinase, making it an ideal candidate for protein kinase C assays in crude tissue extracts, ensuring minimal background interference [1] [2].