A sensitive and rapid method for the determination of protein by the resonance Rayleigh light-scattering technique with Pyrogallol Red

The resonance Ravleigh light-scattering (RRLS) technique was used to develo p a simple, sensitive and selective method for the determination of protein s. The method is based on the interaction between proteins and Pyrogallol R ed (PR) in the pH range 3.6-4.2. which causes a substantial enhancement of the resonance scattering signal of PR in the wavelength range 300-450 nm wi th the maximum scattering peak located at 347 nm. With this method, 0.25-13 mug ml(-1) of bovine serum albumin (BSA). 0.25-10 mug ml(-1) of human seru m albumin (HSA) and 0.25-13 mug ml(-1) of human immunoglobulin G (IgG) can be determined. and the detection limits, calculated as three times the stan dard deviation of nine blank measurements, for BSA, HAS and IgG were 51, 48 and 57 mug l(-1), respectively. Moreover, the method shows almost no prote in-to-protein variability and is free from interference from many amino aci ds and metal ions. The method. with high sensitivity, selectivity and repro ducibility, was satisfactorily applied to the determination of the total pr otein in human serum and saliva samples. Mechanism studies indicated that P R can bind to BSA depending mainly on electrostatic forces, and this intera ction can encourage the J-aggregation of PR, which results in enhanced Rayl eigh light-scattering in the PR-protein system.