Fatty-acid spin probe interactions with erythrocyte ghosts and liposomes prepared from erythrocyte ghosts |
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Authors: | Larry M. Gordon Frank D. Looney Cyril C. Curtain |
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Affiliation: | (1) Anesthèsia Service, J. L. Pettis Veterans Administration Hospital, 92357 Loma Linda, California;(2) CSIRO Division of Biotechnology, 3168 Clayton, Victoria, Australia |
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Abstract: | Summary 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 responsible for probe uptake. Saturation occurs in both systems with increasing P/L, and, at higher loading (e.g., P/L=1/360 for ghosts and liposomes), the probe inserts itself at initially dilute sites to form a class of low-affinity sites consisting of clusters of variable size. At still higher P/L ranges (>1/100), much increased probe uptake was observed in ghosts than in liposomes, which was attributed to another class of low-affinity sites, representing nonspecific interactions of I(12,3) with membrane proteins. The nature of the spectral components and ultrafiltration experiments with ghosts labeled at high P/L indicate that both dilute and clustered I(12,3) are due to membrane-incorporated probe. |
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Keywords: | erythrocyte ghosts liposomes radical interactions protein lipid domains fluidity electron spin resonance spin probes |
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