What methods are there to identify protein?

1 kjeldahl nitrogen determination method

According to the fact that the content of nitrogen in protein molecule is constant (average is 16%), after determining the content of nitrogen in the sample, the content of protein in the sample can be calculated.

2 biuret method

Flynn-phenol reagent method

Flynn-phenol reagent includes two reagents: basic copper reagent, mixed reagent of phosphomolybdic acid and phosphotungstic acid. Experiment of biuret formation by alkaline copper reagent and protein. Phenol groups (tyrosine) reacted in protein can easily reduce phosphomolybdic acid and phosphotungstic acid to blue molybdenum blue and tungsten blue under alkaline conditions, and the generated blue depth is directly proportional to the content of protein. The protein content can be determined by measuring the light absorption values at 650nm and 660nm.

4 ultraviolet absorption method

Tyrosine and tryptophan have the maximum absorption at about 280nm. Because the contents of these amino acids in various protein are similar, the absorption value at 280nm is positively correlated with the concentration. It can be used to determine the concentration of protein.