betadex and dimyristoylphosphatidylglycerol

The interaction of a cationic photosensitizer Safranin-O with liposome membranes having similar surface charge (negative) but differing in the presence of saturation on the lipid side-chain has been studied. To this end, dimyristoyl-l-R-phosphatidylglycerol (DMPG) and 1,2-dioleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DOPG) phospholipids were employed to prepare small unilamellar vesicles. The dye is found to bind in the headgroup region of both the liposome membranes with significantly higher affinity to DOPG lipid containing unsaturated side chain. The effects of various cyclodextrins (CDs) on the stability of the probe-bound liposome membranes have also been investigated using steady-state and picosecond-resolved fluorescence as well as dynamic light scattering techniques. The modulations of the fluorescence properties of the lipid-bound dye were exploited to rationalize the membrane destabilization following interaction with the cyclodextrins. Experimental results reveal the selective interaction of DMPG membrane with CDs leading to rupture of the integrated structure of the liposome units accompanying release of the bound probe to the bulk aqueous phase. On the contrary, no discernible interaction of the CDs was observed with DOPG liposome membrane. Our results also show the differential extents of interaction of various CDs (α-CD, β-CD, methyl-β-CD, and γ-CD) with DMPG leading to varying degrees of release of the bound-dye molecule.

Topics: alpha-Cyclodextrins; beta-Cyclodextrins; Drug Liberation; gamma-Cyclodextrins; Kinetics; Phenazines; Phosphatidylglycerols; Photosensitizing Agents; Solutions; Spectrometry, Fluorescence; Static Electricity; Unilamellar Liposomes

Fluorometric measurements are exploited to explore the binding interactions of nile red (NR) with anionic lipid dimyristoyl-L-α-phosphatidylglycerol (DMPG), zwitterionic lipid dimyristoyl-L-α-phosphatidylcholine (DMPC) as well as neutral cyclic oligosaccharide β-cyclodextrin (β-CD) solutions. The binding constants are found to be quite high and comparable (within a factor of five). Series of spectral techniques like steady state fluorescence and fluorescence anisotropy study, micropolarity study, quenching study and time resolved experiments reveal that the addition of β-CD to the probe-lipid complexes results in weakening of the lipid-probe interaction and formation of probe-β-CD inclusion complexes leading to the removal of some of the probe (NR) molecules from the lipid environments. The extent of removal of NR is, however, more from DMPG than DMPC lipid. The phenomena are explained from the concept of competitive binding of the probe between the lipids and β-CD. Since lipids are the principal constituents of the cell walls, the work might make a foundation for the possible removal of excess of molecules like nile red adsorbed on the cell walls.

Topics: Adsorption; beta-Cyclodextrins; Binding, Competitive; Coloring Agents; Dimyristoylphosphatidylcholine; Fluorescence Polarization; Oxazines; Phosphatidylglycerols; Time Factors

The complexation of beta-cyclodextrin with monolayers of cholesterol, DMPC, DMPG, and mixtures of those lipids has been studied using Brewster microscopy, PMIRRAS, and ab initio calculations. An oriented channel-like structure of beta-cyclodextrin, perpendicular to the air/water interface, was observed when some cholesterol molecules were present at the interface. This channel structure formation is the first step in the cholesterol dissolution in the subphase. With pure DMPC and DMPG monolayers, weaker, less organized complexes are formed, but they disappear almost completely at high surface pressure, and only a small amount of phospholipid is dissolved in the subphase.

Topics: Air; beta-Cyclodextrins; Chemistry, Physical; Cholesterol; Computer Simulation; Dimyristoylphosphatidylcholine; Membranes, Artificial; Molecular Conformation; Phosphatidylglycerols; Phospholipids; Spectroscopy, Fourier Transform Infrared; Surface Properties; Water