0000000000020688
AUTHOR
Jesús Pedrós
Interaction of quinine with negatively charged lipid vesicles studied by fluorescence spectroscopy Influence of the pH
Abstract The interaction of quinine with dimyristoylphosphatidic acid (DMPA) and dimyristoylphosphatidyl glycerol (DMPG) small unilamellar vesicles in the gel phase was studied by steady-state fluorescence spectroscopy at pHs 7, 6, 5 and 4 and 20°C. In aqueous solution, with excitation at 335 nm, the emission fluorescence spectrum of quinine varied with pH reflecting the occurrence of different charged species of the drug. In all cases, the emission maximum centered at 383 or 443 nm shifted to lower wavelength in the presence of vesicles. This indicates that the membrane-bound state quinine is in an environment of low polarity. Drug monocationic species were deeply buried in DMPG relative t…
Binding of basic amphipathic peptides to neutral phospholipid membranes: a thermodynamic study applied to dansyl-labeled melittin and substance P analogues.
A thermodynamic approach is proposed to quantitatively analyze the binding isotherms of peptides to model membranes as a function of one adjustable parameter, the actual peptide charge in solution z(p)+. The main features of this approach are a theoretical expression for the partition coefficient calculated from the molar free energies of the peptide in the aqueous and lipid phases, an equation proposed by S. Stankowski [(1991) Biophysical Journal, Vol. 60, p. 341] to evaluate the activity coefficient of the peptide in the lipid phase, and the Debye-Huckel equation that quantifies the activity coefficient of the peptide in the aqueous phase. To assess the validity of this approach we have s…
A fluorescence spectroscopy study of the interaction of monocationic quinine with phospholipid vesicles Effect of the ionic strength and lipid composition
Abstract The interaction of monocationic quinine with zwitterionic dimyristoyl phosphatidylcholine (DMPC) and mixed negatively-charged dimyristoylphosphatidyl glycerol (DMPG) DMPC small unilamellar vesicles in the liquid-crystalline phase was investigated by steady-state fluorescence spectroscopy at pH 7 and 37°C. The maximum fluorescence emission peak at 383 nm, upon excitation at 335 nm, shifts to lower wavelength and decreases its intensity as the ratio between the total lipid and quinine concentrations increases. This indicates that in the membrane-bound state quinine is in an environment of low polarity, more deeply buried when anionic DMPG is present in the vesicle. For monoprotonated…