Hemoglobin Reactions as Interfacial Phenomena

Abstract

ConclusionsThrough the use of flash irradiation and high speed potentiostatic monitoring, currents clearly related to electron photoemission have been observed. Although the expected dependences on electrode potential and scavenger presence were obtained, the time dependence of the observed flash photocurrents was found to be governed primarily by the prevailing electrochemical cell time-constant to such a large degree that they can only be explained as capacitive charging currents in response to a virtually instantaneous flash-induced electron injection into the double layer.The charging current model for the photoemissioninitiated currents, and the experimental results on which it is based, are consistent with the known chemical and physical processes that actually occur for a wide range of scavenging situations. Furthermore, for certain specialized cases (e.g., NO~-) in which the secondary scavenging reactions proceed sufficiently slowly, the time dependence of flash photocurrents can be related directly to the reaction rates of scavenging intermediates. In these cases, useful chemical information concerning eaq-chemistry and scavenging reactions can be obtained. ABSTRACTThe reactions of hemoglobin with various ligands lead to conformational changes in the macromolecule.The free energy of these changes can be eestimated in terms of the surface free energy of a miereemulsion droplet of the same size and surface charge as the hemoglobin molecule. Calculations on the basis of this model yield an equilibrium constant that varies with pH, as in the acid and alkaline Bohr effects, and with the ionic strength. The model also provides a physical meaning for the empirical constant in the oxygen binding equation, as well as some insight into the dissociation equilibrium of the hemoglobin tetramers. This approach to equilibria involving globular proteins should be useful for estimating the effects of conformational changes and subunit interactions in other systems.The study of macromolecules as interracial systems, i.e., the chemistry of hydrophilic colloids, was the first * Electrochemical Society Active Member.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.15.241.167 Downloaded on 2015-03-10 to IP

Composite Films of Surfactants, Nafion, and Proteins with Electrochemical and Enzyme Activity

“…c tw = this work. d For comparison with CV data where diffusion control pertains, k s was estimated from the standard heterogeneous rate constant ( k o ‘) by using k o‘ = d k s , where d is the film thickness …”

A surface free energy model for protein structure in solution

“…Furthermore, the model shows that the empirical Hill coefficient in the oxygen binding equation is not a constant, as has been demonstrated by Roughton et al (1955). The coefficient is simply related to and behaves as a Gibbs surface excess (Blank, 1976(Blank, , 1980b.…”

Soft-Lithography-Mediated Submicrometer Patterning of Self-Assembled Monolayer of Hemoglobin on ITO Surfaces

“…This modified electrode was then used to study the adsorption behavior of Hb on an ITO surface. Hb (human) was obtained from Sigma and dissolved with Milli-Q water to obtain solutions with different concentrations and pH value of 5.3, which were in the pH range of native Hb . After the ITO surface was equilibrated with Hb solution, followed by rinsing with Milli-Q water and drying under a stream of purified N 2 gas, the frequency was recorded as F 2 .…”