Irradiation of porphyrins modulate the structure of human serum albumin*

 Recent research in our group has revealed that irradiating metal-free porphyrins binding to globular proteins can cause changes in the structure of the polypeptides under certain conditions. In this study we investigated the impact of irradiation of a series metal protoporphyrin on the structure of HSA at pH 7.0. UV-Vis absorption, fluorescence, fluorescence lifetime and circular dichroism of HSA with a series of metal PPIXs including Fe, Mg, Mn, Sn and Zn were measured. Spectra were recorded by using a spectrophotometer to observe bleaching of the PPIXs.  Fluorescence and fluorescence lifetime were taking place to monitor the changes of Trp 214 in HSA. CD spectroscopy was carried out to estimate the change in the secondary structure of the protein. 

Our results show that the fluorescence analysis results indicate that PPIX can interact with environments of Trp 214 in HSA. Binding of PPIX to HSA with irradiation leads to bleaching of the porphyrins in the region of Trp 214 at pH 7.0