Hemoglobin-facilitated diffusion of oxygen: Interfacial and thickness effects

The equations of facilitated diffusion were solved numerically for steady state diffusion of oxygen across membranes of hemoglobin and myoglobin. An interfacial resistance was included in the boundary conditions and the dependence of the solutions on membrane thickness and interfacial conductance was studied. The data of Wittenberg on millipore membranes was fitted adequately if a tortuosity factor for the millipore membranes was taken into account. Comparison of the solutions with Wittenberg's data shows that the interfacial conductances must be large, 10-8 mole/cm2-sec-mm Hg or larger. More accurate estimates of interfacial conductance could be obtained from data on thin membranes, 1-5 [mu], but such data are not available. It was found that the concentration profiles are not independent of thickness and that the facilitation decreases as the membrane thickness decreases. The latter occurs even for zero interfacial resistance and hence cannot be attributed to a back pressure effect. The effect is present because the dissociation reaction at the low PO2 boundary increasingly becomes the limiting factor in the establishment of the steady state as L decreases.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34087/1/0000368.pd

Numerical study of oxygen uptake by layers of hemoglobin solution

Numerical solutions have been obtained for the equations describing O2 uptake by layers of concentrated hemoglobin solution 0.25, 0.5, 1, 1.6, 2, 3.6, 5, 10, and 20 [mu] thick. The results indicate that the diffusion of oxyhemoglobin has almost no effect on the rate of oxygenation of the 0.25 [mu] layer, but its influence increases with increasing layer thickness, so that it shortens the time required to reach 50% saturation in the 1.6 [mu] layer by 23 % and in the 5[mu] layer by 34%. For the 1.6 [mu] layer, which might be considered a model red blood cell, the results suggest that the rate at which O2 reacts with hemoglobin is of primary importance early in the uptake process, but that later the diffusion of O2 into the deeper parts of the layer becomes rate-limiting.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32682/1/0000049.pd

Determination of Fluorescence Polarization of Membrane Probes in Intact Erythrocytes: Possible Scattering Artifacts

The anisotropy of the fluorescence of diphenylhexatriene has been reported to be less in the membranes of intact erythrocytes than in erythrocyte ghost membranes or in membranes prepared from erythrocyte lipids. Evidence is presented that this may be an artifact due to the intense light scattering by the intact erythrocytes