Microelectrode studies of facilitated O2 transport across hemoglobin and myoglobin layers

Experimentally measured PO2 profiles across layers of hemoglobin and myoglobin solutions were compared with profiles predicted from facilitated transport theory assuming chemical equilibrium. Measurements across myoglobin layers were in excellent agreement with theory, but measurements across hemoglobin layers departed from theory at low PO2. This departure was greatest for salt-free hemoglobin solution, which may be caused by an electrical potential formed by a pH gradient in the layer as oxyhemoglobin is deoxygenated.