Investigation of phycocyanin-membrane interaction: Promotion of membrane interactions

Abstract

1. 1. In a continuing investigation of phycocyanin-membrane surface interaction, fluorescence quenching experiments were performed with a mixture of two populations of fluorescence probe-encapsulated phospholipid bilayer vesicles in the presence and absence of phycocyanin. 2. 2. These membrane vesicles were prepared with 1,2-dimyristoyl phosphatidylcholine (DMPC), cholesterol and a probe molecule. 3. 3. A fluorophore was encapsulated in one population of membrane vesicles, while a quencher was encapsulated in another population of membrane vesicles. 4. 4. The result was compared with those of experiments in the presence of other biomolecules, including albumin, cytochrome c, hemoglobin, myoglobin or RNA. 5. 5. Interestingly, a one-third reduction of the fluorescence intensity was observed in the mixture of these two populations of membrane vesicles in phycocyanin's presence. 6. 6. In contrast, the other biomolecules caused no significant reduction in the fluorescence intensity. 7. 7. These findings were evidence of a phycocyanin-induced membrane perturbation. 8. 8. This was further demonstrated by a phycocyanin-induced change in the thermotropic behavior of DMPC vesicles, as measured by differential scanning microcalorimetry. 9. 9. Such a unique property of phycocyanin is believed to be associated with its known membrane surface-interacting character. 10. 10. A possible phycocyanin-modulated membrane-membrane interaction was discussed.