Fatty acid spin-label probes

Monolayer Studies of Pure Nitroxide Fatty Acid Spin-Label Probes... 

Ottaviani and various coworkers have in the past often used a spin probing/ spin labeling approach to study self-assembled soft matter systems. In a recent paper they describe the complexes formed between cationic surfactants and hydrophobic ally modified anionic polymers. Analyzing the changes in dynamics as well as environment (hydrophobicity) of the long-chain fatty acid spin probe... 

In addition to calorimetry, information to establish the mode of adsorption is often obtained spectroscopically. Changes in the optical properties of (groups on) the surface or the adsorptive may be monitored. As an Illustration of the former. Rochester studied adsorption from the gas euid liquid phase on rutile (TiOj) and used infrared spectroscopy to distinguish between attachment at different surface hydroxyls. As an example of an ESR study, McBride investigated the adsorption of fatty acids on amorphous alumina from methanol by labelling them with a spin probe. Relevant information could be... 

To determine the shape of the hydrophobic barrier of bilayer membranes, fatty acids and PC molecules spin labeled with nitroxides at various positions along the lipid chains were diffused into vesicles and their solvent-sensitive isotropic coupling constants were measured [54]. Results are plotted in Figure 5 in terms of distance of the probe from the bilayer center. Also shown is the profile of the dielectric constant along the membrane normal evaluated from the fluorescence lifetime distribution of fluorescence probes in PC liposomes [55]. These data correlate well with results from neutron diffraction studies that map the positional distribution of water and lipid moieties along the bilayer normal [56]. 

The interior microenvironment of BS-L micelles has been probed by fluorescence spectroscopy using a variety of large probes with both common BS-egg and -synthetic L micelles as functions of temperature [223,232,238], NMR of [ H]lecithins [235,237] differential scanning calorimetry [236], X-ray scattering [233], and electron spin resonance of spin-labels incorporated into lecithin and fatty acid chains [232]. 

The spin-labeled cardiolipin molecule is a phospholipid, containing a polar "head" group and four fatty acid hydrophobic "tails". It has been incorporated into lipid bilayers as a probe of molecular flexibility and mobility in model membranes.24... 

Electron microscopy shows that polymerisation of diacetylene lipids which have been dispersed in water to form liposomes does not alter the structure of the liposomes. They also remain osmotically active. Polymerisation reduces the permeability of the liposomes to glycerol. This may be a consequence of triple bonds being converted into less polar double bonds. Polymerisation also reduces the propensity of liposomes to precipitate, the more so the lower the temperature. E.s.r. measurements with labelled fatty acid probes did not reveal any changes in the fluidity of the bilayer after its polymerisation. However this may be because polymer and remaining monomer s eparate into domains and the spin labels lie in the monomer domain. 

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