EFFECT OF HEMOGLOBIN ON THE LATERAL DIFFUSION OF HUMAN BRYTHROCYTE MEMBRANE LIPIDS
血红蛋白对人红细胞膜脂质分子侧向运动的影响

To confirm the restriction of membrane fluidity by Hb- membrane interaction, we furthermore studied this phenomenon with the fluorescence photobleaching recovery (FPR) technique. By this method the lateral diffusion constant (D) of membrane lipids were measured.When ghosts were incubated with sonicated vesicles of NBD-PE in isotonic buffer, no significant differences of the D values were observed among ghosts alone, Ghosts-OxyHb and Ghosts-MetHb. But as the incubation condition was changed to hypotonic buffer the differences were clearly observed. NBD-PE molecules are intercalated mainly into the exterior half of the bilayer of resealed ghost, and Hb molecules are bound to the cytoplasmic side of the erythrocyte membrane. Thus no effect of Hb on D value was noted in the isotonic condition. For leaky ghosts in the hypotonic condition the fluorescence probe molecules were distributed both sides of the membrane, therefore through Hb -membrane interaction the D value of NBD-PE molecules was affected. This presumption was confirmed based on the fluorescence quenching experiment It was shown that MetHb induced more restriction of the mobility of the lipid molecules as to compare to OxyHb. This is accordance with the phenomenon that MetHb has stronger interaction with the erythrocyte membrane.