Kinetics of incorporation/redistribution of photosensitizer hypericin to/from high-density lipoproteins.

By means of fluorescence spectroscopy we have studied the kinetics of interaction of a photosensitizer hypericin (Hyp) with high-density lipoproteins (HDL). Hyp is incorporated into HDL molecules as monomer till ratio Hyp/HDL ∼8:1 and above this ratio forms non-fluorescent aggregates. This number is different from that found in the case of Hyp incorporation into low-density lipoprotein (LDL) molecules (8:1 vs 30:1).

Alcohols are inhibitors of Saccharomyces cerevisiae multidrug-resistance pumps Pdr5p and Snq2p.

The effect of alcohols on cell membrane proteins has originally been assumed to be mediated by their primary action on membrane lipid matrix. Many studies carried out later on both animal and yeast cells have revealed that ethanol and other alcohols inhibit the functions of various membrane channels, receptors and solute transport proteins, and a direct interaction of alcohols with these membrane proteins has been proposed. Using our fluorescence diS-C3 (3) diagnostic assay for multidrug-resistance pump inhibitors in a set of isogenic yeast Pdr5p and Snq2p mutants, we found that n-alcohols (from ethanol to hexanol) variously affect the activity of both pumps.

Kinetics of hypericin association with low-density lipoproteins.

Steady-state and time-resolved fluorescence spectroscopy have been used for the study of the incorporation kinetics of hypericin (Hyp) into low-density lipoproteins (LDL). Biphasic kinetics of Hyp association with LDL was observed when solutions of Hyp and LDL were mixed at various concentration ratios. The rapid phase of Hyp incorporation is completed within seconds, while the slow phase lasts several minutes.

Interaction dynamics of hypericin with low-density lipoproteins and U87-MG cells.

The natural photosensitizer hypericin exhibits potent properties for tumor diagnosis and photodynamic therapy. Fluorescent properties of hypericin along with various technical approaches have been used for dynamic studies of its interaction with low-density lipoprotein and U87 glioma cells. Evidences for hypericin release from low-density lipoprotein towards cells plasmatic membrane are addressed.