title: Theory of the rotational contribution to facilitated diffusion.
abstract: Gros and others have recently shown experimentally that the facilitated diffusion of protons carried by a form of haemoglobin is enhanced by rotational diffusion of the carrier, whereas facilitated diffusion of oxygen by the same carrier is not. In this paper the theory of facilitated transport by rotating carriers is developed from first principles. The theory confirms Gros's findings that (i) the rotational contribution appears only when the angle of rotational diffusion over the average time the proton remains bound is small and (ii) under these conditions rotation enhances the normal translational contribution by a factor 1/2 at the lowest carrier concentrations. The theory also shows that there must be a rotational boundary layer.
mesh_terms: D001665:Binding Sites; D001692:Biological Transport; D006454:Hemoglobins / Q000378:metabolism; D008433:Mathematics; D011522:Protons; D012399:Rotation
chemical_list: D006454:Hemoglobins; D011522:Protons