Protein estimation refers to measuring the total level of protein or the concentration of protein in a solution. It usually involves Biochemical assays in combination with Physical methods like spectrophotometry or colorimetry. One of the earliest method developed is that of Lowry protein assay. The Cu+ ions which are produced by the oxidation of peptide bonds (present in proteins) react with the FolinCiocalteu reagent in alkaline conditions. The reduction of the Folin reagent produces a color change in the solution. This change is proportional to the protein concentration and can easily be measured using colorimetry. The Bicinchoninic acid assay also known as BCA was a further development of the Lowry method. The stock BCA solution has all the required reagents and an alkaline pH of 11.25. Here, the bicinchoninic acid chelates with Cu+ ion forming a purple-colored complex. The protein of interest can be quantified by comparing the absorption spectra with the protein solutions of known concentration. The Bradford assay, on the other hand, is based on the absorbance shift of the dye Coomassie Brilliant Blue G-250 under an acidic condition where the red dye shifts into its bluer form on binding the protein being assayed.

 

Biomall offers a range of these reagents/solutions/ kits which are required for protein estimation and assays.