A study on photochemical behavior of lysozyme-bromophenol blue complex and its analytical application

It was found that macromolecular complexes were formed between lysozyme and bromophenol blue (BPB) with the electrostatic attraction in acetate medium (pH 6.5). The binding constant and the number of binding site for lysozyme-BPB complex were obtained, and the thermodynamic parameters were given. In addition, a remarkable enhancement of resonance light scattering (RLS) intensity for the macromolecular complex was observed with a scattering peak at 336 nm. And the increment of RLS intensity was proportional to the concentration of lysozyme in the range of 5 ng ml−1 to 10.0 μg ml−1. The influence of experimental conditions including pH, BPB concentration, and ionic strength on RLS system were tested, especially the effect of temperature was examined in detail. The proposed method was successfully applied to determine lysozyme in human saliva and tear samples without any special pretreatment. Compared with other methods the proposed method is of higher sensitivity and wider linear range.