Fatty-acid spin probe interactions with erythrocyte ghosts and liposomes prepared from erythrocyte ghosts.
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 less than 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 (greater than 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.
Gordon
L M
LM
Anesthesia Service, J.L. Pettis Veterans Administration Hospital, Loma Linda, California 92357.
Looney
F D
FD
Curtain
C C
CC
D001665:Binding Sites; D003497:Cyclic N-Oxides; D004578:Electron Spin Resonance Spectroscopy; D004910:Erythrocyte Membrane / Q000378:metabolism*; D005227:Fatty Acids / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D008081:Liposomes; D008954:Models, Biological; D015335:Molecular Probes; D013113:Spin Labels; D014462:Ultrafiltration
D003497:Cyclic N-Oxides; D005227:Fatty Acids; D008081:Liposomes; D015335:Molecular Probes; D013113:Spin Labels; C005072:5-doxylstearic acid