Frank D. Looney

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An electron spin probe study was made of the effect of a number of mitogenic agents on the ordering and state of aggregation of the plasma membrane lipids of lymphocytes. These agents, which included phytohemagglutinin, Concanavalin A, the calcium ionophore A23187 and periodate, caused a 20% decrease in lipid ordering in the region of the bilayer probed by(More)
Changes in the ordering and motion of lipids in response to changes in the external solute concentration have been studied by using the 5-nitroxide stearate (5NS) and 16-nitroxide stearate (16NS) spin probes in the plasma membrane of the halotolerant unicellular alga Dunaliella salina. Increases in ordering of the 5NS probe and decreases in motion of the(More)
ESR spectroscopy is a sensitive method which can be used to monitor a wide range of changes in and near the plasma membranes of lymphoid cells during such events as ligand-induced receptor patching and capping, activation and endocytosis and phagocytosis. The advantages of the technique are rapidity, sensitivity, small sample size (10(6)-10(7) cells), and(More)
Purified human Ia molecules were labelled with maleimide or isothiocyanate spin labels or by reacting "TEMPAMINE" spin label with the neuraminic acid of their carbohydrate residues. It was found that increasing the ionic strength from 0.05 to 0.75 markedly increased the dipolar interaction between the maleimide-attached labels, but no effect was found of(More)
A model has been developed for 5-nitroxide stearate, I(12,3), distribution in human erythrocyte ghosts which accurately predicts ESR spectral alterations observed with increased probe/total lipid (P/L) at 37°C. This spin probe occupies a class of high-affinity, noninteracting sites at low loading. Saturation occurs with increasing probe concentration, and,(More)
It was shown using spin-labelled probes that challenge of sensitized rat peritoneal mast cells results in clustering of sphingolipids located in the outer leaflet of the plasma membrane bilayer. This clustering is partially inhibited by antiallergic drugs of the chromone type. It is hypothesized that the sphingolipid clustering may be involved in the Ca++(More)
An iterative spectral subtraction technique has been developed which accurately estimates the proportion of 'dilute' and 'clustered' I(12, 3) (i.e., 5-nitroxide stearate) in human erythrocyte ghosts at 37 degrees C, even if subtractant spectra free from probe-probe interactions cannot be measured due to technical limitations. Gordon et al. ((1985) J.(More)
Spectral parameters of spin-labelled phosphatidylcholine, ceramide and cerebroside in the plasma membranes of human blood lymphocytes were measured before and after treatment with various ligands, which included concanavalin-A and phytohemagglutinin. It was found that ligand treatment led to a significant decrease in order of the hydrocarbon chains of the(More)
A model for the binding of 5-nitroxide stearate, I(12,3). to human erythrocyte ghosts was developed by comparing spin probe interactions with ghosts and liposomes prepared from ghosts. At low probe/lipid (P/L<1/2500), I(12,3) binds to a similar class of high-affinity, noninteracting sites in both ghosts and liposomes, indicating that lipid moieties are(More)