[R-phycoerythrin: a natural ligand for detoxifying cadmium ions and a tunnel matrix for synthesis of cadmium sulfide nanoparticles].

As evidenced by ion-selective electrode potentiometry, the hexameric R-phycoerythrin (RPE) molecule binds 20-4000 cadmium ions (Cd2+) depending on Cd2+ concentration in the solution. Cadmium ions bound to RPE serve as nuclei of cadmium sulfide crystallization in the presence of sulfide ions. According to spectrometric, electron-microscopic and capillary electrophoresis data, the particles are heteroaggregates of 3.2 x 6 nm in size. The fact that the particle size fits the size of the central tunnel of the RPE molecule and the similarity between the electrophoretic patterns of free RPE and the RPE-CdS complex indicate that the tunnel space, limiting the crystal growth, is the most probable site of nanoparticle formation. Properties of the nanoparticles can be modified by changing temperature, pH, etc. It is concluded that RPE can be used as a reagent for detoxification of cadmium ions and a matrix for synthesis of elongated CdS nanoparticles.