On the surface properties of oleate micelles and oleic acid/oleate vesicles studied by spin labeling.

Dilute aqueous systems composed of sodium oleate micelles and sodium oleate/oleic acid vesicles were investigated as a function of pH by electron spin resonance spectroscopy with TEMPO-stearate TEMPO-stearamide as well as with a positively charged water soluble spin label, TEMPO-choline. The dynamics of the three TEMPO-spin labels were found to be sensitive to changes in the interfacial region of the aggregates as a function of pH. The results obtained are consistent with the formation of a hydrogen bond network (RCOO(-)↔HOOCR) at the surface of the sodium oleate/oleic acid system in the course of the transformation of micelles into the closed bilayers (vesicles).

An ESR characterization of micelles and vesicles formed in aqueous decanoic acid/sodium decanoate systems using different spin labels.

Aqueous decanoic acid/sodium decanaote systems were studied as a function of pH and concentration, up to 0.3 M decanoic acid/sodium decanoate, by electron spin resonance (ESR) spectroscopy using three different amphiphilic spin labels. The distribution of the spin labels between vesicles and micelles as well as their dynamic properties were determined by quantitative analysis of the ESR spectra using two novel simulation software packages.

Spin labelling study of interfacial properties of egg-phosphatidylcholine liposomes as a function of cholesterol concentrations.

In order to gain insight into interfacial properties of liposomes composed of egg-phosphatidylcholine (egg-PC) and dihexadecyl-phosphate (DHP) as a function of 0, 8, 15, 29, 38, 45mol% of cholesterol, dynamic properties of two long-chain spin labels: TEMPO-stearate (2,2,6,6-tetramethylpiperidine-1-oxyl-4-yl)-octa-decanoate) and TEMPO-stearamide (2,2,6,6-tetramethylpiperidine-1-oxyl-4-yl)-octa-decanamide) were studied by CW-ESR spectroscopy. These spin labels reflect motional properties in the region of phospholipid head-groups. Two different environments of TEMPO-stearate were determined at 29, 38 and 45mol% of cholesterol.

Spin-labelling study of interactions of ovalbumin with multilamellar liposomes and specific anti-ovalbumin antibodies.

Ovalbumin (OVA) has been used continuously as the model antigen in numerous studies of immune reactions and antigen processing, very often encapsulated into liposomes. The purpose of this work was to study the possible interactions of spin-labelled OVA and lipids in liposomal membranes using electron spin resonance (ESR) spectroscopy. OVA was covalently spin-labelled with 4-maleimido-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO-maleimide), characterized and encapsulated into multilamellar, negatively charged liposomes.

Hydrophobic barrier in liposomes studied by FT-ESEEM.

An improvement of the electron spin echo envelope modulation technique (ESEEM) for studying the hydrophobic barrier in lipid membranes was proposed. Water penetration depth into the lipid bilayer composed of egg-phosphatidylcholine and dicetylphosphate was studied. For this purpose the stearic acid spin probes with nitroxide moiety at different positions on the acyl chain were dissolved in the bilayer of liposomes prepared in buffer solution with D2O.