Biopharma

PROTEIN ASSAY QUANTITATIVE METHODS Copper Ion Based Assays (Lowry & BCA)   In copper ion based assay protein solution mixed with alkaline solution of copper salt. In  alkaline conditions, cupric ions (Cu2+) react with peptide bonds and reduce to cuprous ions (Cu+). If the alkaline copper is in excess over the amount of peptide bonds, some of the cupric ions (Cu2+) will remain unbound to the peptide bonds and are available for detection. Protein assays based on copper ions can be divided into two groups, assays that detect reduced cuprous ions (Cu+) and assays that detect the unbound cupric (Cu2+) ions. The cuprous ions (Cu+) are detected either with bicinchoninic acid (BCA) or Folin Reagent (phosphomolybdic / phosphotungstic acid) as in the protein assays based on Lowry method.  Lowry Method As discussed above its two step reaction in first step Cu+2 reduced under alkaline condition to Cu+1 which form complex with peptide bonds. In second step  Cuprous ions (Cu+) pep