PubMed Health⌕ Search

Biomedical subjects

A Spisni

Publications and source records attributed to A Spisni.

11 recordsLinked to original sources
PubMed1992

The chemical synthesis of N-[1-(2-naphthol)]-phosphatidylethanolamine, a fluorescent phospholipid for excited-state proton transfer studies.

A procedure for the preparation of N-[1-(2-naphthol)]-phosphatidylethanolamine (NAPH-PE) has been developed. The synthesis is based on the Schiff base formation between the NH2 of the phospholipid and the aldehyde moiety of 2-hydroxy-1-naphthaldehyde. Then selective reduction of the imine is used to obtain the stable secondary amine, NAPH-PE. Formation of the intermediate Schiff base and the final product is confirmed by 13C- and 1H-NMR. Similar to free 2-naphthol, the excited-state pKa (pKa*) of its phospholipid derivative appears to be significantly lower than the ground-state pKa. At pH 7.4, the excitation spectrum of NAPH-PE shows no deprotonated species in the ground-state, while the emission spectrum presents a significant contribution of this species. Thus the fluorescent phospholipid exhibits the typical behavior of excited-state proton-transfer probes. NAPH-PE is found to incorporate in dimyristoyllecithin (DML) vesicles. The emission spectrum of the probe inserted in the liposomes is affected by acetate used as a proton acceptor. These properties should also be manifest in other lipid bilayers (e.g., plasma membranes of cells) and used for excited-state proton transfer studies.

Fluorescence↗
PubMed1991

Identification of the peroxidation product hydroxystearic acid in Lewis lung carcinoma cells.

Whole cell lipids were extracted from the Lewis lung carcinoma in vitro line C108. The fatty acids were derivatized to methylesters in order to identify endogenous oxidized derivatives by gasmass spectroscopy. The presence of 9-hydroxystearic acid and 10-hydroxystearic acid was thus evidenced for the first time in cultured mammalian cells. Moreover a linear correlation was found between the concentration of these products expressed as percentage of total fatty acid methylesters and the cell density in tissue culture flasks. This finding suggests an involvement of hydroxystearic acid in cellular functions related to the cell density in monolayer cultures.

Animals↗
PubMed1991

Fluorescence and CD studies on the conformation of the gastrin releasing peptide in solution and in the presence of model membranes.

The conformation of the heptacosapeptide hormone, gastrin releasing peptide, has been studied in buffer and in the presence of lipids, using static and dynamic fluorescence and CD. The results obtained show that, in buffer, the hormone exists in a collection of flexible, random coil type conformers, characterized by a beta-turn between residues 14-19. On the other hand, organic solvents can induce some degree of ordered secondary structure in the peptide chain. The marked changes, observed in CD and fluorescence spectra upon addition of lysolecitin micelles and dimyristoylphosphatidylserine vesicles, clearly show that the peptide interacts with lipids, assuming a lipid specific configuration. Interestingly, no significative spectroscopic changes are produced by exposure to dimyristoylphosphatidylcholine vesicles both in the gel and liquid-chrystalline phases, suggesting a requirement for negatively charged lipids during the process of hormone-membrane interaction.

Amino Acid Sequence↗
PubMed1979

Effect of phospholipase A2 on purified gastric vesicles.

The phospholipid and fatty acid composition and role of phospholipids in enzyme and transport function of gastric (H+ + K+)-ATPase vesicles was studied using phospholipase A2 (bee venom). The composition (%) was phosphatidyl-choline (PC) 33%; sphingomyelin (sph) 25%; phosphatidylethanolamine (PE) 22%; phosphatidylserine (PS) 11%; and phosphatidylinositol (PI) 8%. The fatty acid composition showed a high degree of unsaturation. In both fresh and lyophilized preparations, even with prolonged incubation, only 50% of phospholipids were hydrolyzed, but the amount of PE and PS disappearing was increased following lyophilization. There was a marked decrease in K+-ATPase activity (75%) but essentially no loss of the associated K+ p-nitrophenyl phosphatase was found. ATPase activity could be largely restored by various phospholipids (PE greater than PC greater than PS). There was also an increase in Mg2+-ATPase activity, partially reversed in fresh preparations by the addition of phospholipids (PE greater than PS greater than PC). Proton transport activity of the preparation was rapidly inhibited, initially due to a large increase in the HCl permeability of the preparation. Associated with these enzymatic and functional changes, the ATP-induced conformational changes, as indicated by circular dichroism spectra were inhibited.

Adenosine Triphosphatases↗