title: Studies on molecular interactions between nalidixic acid and liposomes.
abstract: The interaction between nalidixic acid sodium salt (NANa) and liposomes prepared from alpha-L-dipalmitoyl-phosphatidylcholine (DPPC) or from its binary mixture with dioleoyl-phosphatidylcholine (DOPC) was studied with differential scanning calorimetry (DSC) and electron paramagnetic resonance (EPR) spectroscopy. We evaluated the role of broadband ultraviolet-B (UV-B) irradiation on the molecular interactions between the lipids and the NANa, and determined the decay-kinetics of the incorporated spin labeled fatty-acid free radicals. Multilamellar and unilamellar vesicles were prepared by sonication and extrusion. The entrapment efficiencies were determined spectrophotometrically. The size-distribution of the liposomes and its change in time was checked by dynamic light scattering (DLS). Our results indicate that NANa mainly interacts with lipid head groups. However, its effect and presumably the formation of the free radicals, induced by broadband ultraviolet-B, is not localized only to the head group region of the lipid molecules. Depending on DOPC content, interaction between the NANa and the lipids modifies the phase-transition parameters of the liposome dispersions.
authors.affiliation: Institute of Biophysics and Radiation Biology, Faculty of Medicine, Semmelweis University, Budapest VIII, P.O. Box 263, Puskin u. 9, H-1444 Budapest, Hungary.
authors.forename: M
authors.initials: M
authors.lastname: Budai
authors.forename: Zs
authors.initials: Z
authors.lastname: Szabó
authors.forename: A
authors.initials: A
authors.lastname: Zimmer
authors.forename: M
authors.initials: M
authors.lastname: Szögyi
authors.forename: P
authors.initials: P
authors.lastname: Gróf
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry* / Q000528:radiation effects; D002152:Calorimetry, Differential Scanning; D004578:Electron Spin Resonance Spectroscopy; D008081:Liposomes; D009268:Nalidixic Acid / Q000008:administration & dosage / Q000737:chemistry* / Q000528:radiation effects; D010316:Particle Size; D010713:Phosphatidylcholines / Q000737:chemistry*; D017319:Photosensitizing Agents / Q000008:administration & dosage / Q000737:chemistry* / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D008081:Liposomes; D010713:Phosphatidylcholines; D017319:Photosensitizing Agents; D015060:1,2-Dipalmitoylphosphatidylcholine; D009268:Nalidixic Acid; C017251:1,2-oleoylphosphatidylcholine