Origin of the root effect in fish Hbs: Moderate proton-dependence of redox potentials suggests steric hindrance dominance


Claire J. Parker Siburt, cps7@duke.edu1, C. Bonaventura2, and A. L. Crumbliss, alc@chem.duke.edu1. (1) Department of Chemistry, Duke University, 124 Science Dr, Box 90354, Durham, NC 27708, (2) Duke University Marine Laboratory, Nicholas School of the Environment, Beaufort, NC 28516
Hemoglobins of some fish exhibit significantly lowered oxygen affinity at low pH, allowing for proton-mediated release of O2. This phenomenon, the Root Effect, serves as a proton-driven pump delivering O2 to the swim bladders and eyes, even against high oxygen pressures experienced at great depths. The structural basis of the extreme pH-sensitivity of Root Effect Hemoglobins is the subject of ongoing debate. We present spectroelectrochemical data demonstrating the effect of pH on the reduction potentials of two Root Effect fish, Spot and Carp. These representative Root Effect Hemoglobins do not show an extreme redox-Bohr effect, but rather a gradual decrease in reduction potential as pH increases. This trend is similar to that observed for non-Root-Effect fish and human Hemoglobins. The difference in pH sensitivity seen between the oxygenation and oxidation processes strongly suggests that steric hindrance is the major determinant of the pH-sensitivity of oxygen binding by Root Effect Hemoglobins.

General Inorganic Chemistry
9:00 AM-1:00 PM, Sunday, April 6, 2008 Morial Convention Center -- Rm. 219, Oral

Division of Inorganic Chemistry

The 235th ACS National Meeting, New Orleans, LA, April 6-10, 2008