Interaction of enzyme-generated species with chlorophyll-alpha and probes bound to serum albumins.

Abstract

Abstract— The interaction of serum albumin‐bound acceptors with enzyme‐generated and protected triplet species was studied in two types of systems. Chlorophyll‐a bound to bovine and human serum albumins is efficiently excited by enzymatically generated triplet acetone and acetaldehyde. When the Chl‐a concentration is much lower than that of the albumin the interaction occurs with chlorophyll in an aggregate in which one Chl‐a is surrounded by several protein molecules. When the Chl‐a concentration is higher than that of the protein, the aggregate contains the proteins and fluorescent chlorophylls in a 1:1 ratio. The excess chlorophylls, although able to interact with the donors, are not fluorescent.In another study, probes bound to various specific sites of serum albumins were used as quenchers of the enzymatically generated triplet acetone. The efficiency of quenching by all the bound probes is equal and in one case even stronger than for the free probes.A model for the interaction of the excited species contained in the enzyme with the acceptor(s) located in the protein is proposed.The present results provide further evidence that enzyme‐generated and protected triplet carbonyl species can interact through a collisional process with acceptors bound to or constituents of macromolecules.