Oxidation of (horse) hemoglobin by copper: an intermediate detected by electron spin resonance.

This research article examines how the oxidation of horse hemoglobin by copper is followed by alterations in electron spin resonance spectra. It reveals that the binding of copper to hemoglobin results in conformational changes in the area of the copper binding site.

Understanding Oxidation of (horse) Hemoglobin by Copper

The study explores the process of oxidation of horse hemoglobin by copper ions (Cu(II)). The changes induced by this process are assessed by looking at the electron spin resonance spectra. Electron spin resonance spectroscopy is a technique used to study materials with unpaired electrons.

• The experiments were conducted using techniques called stopped-flow and freeze-quenching. The stopped-flow technique allows the study of rapid chemical reactions, while freeze-quenching is used to rapidly cool a sample and hold its components in place.
• The study states a second-order rate constant greater than 5 X 10(5) mol-1 s-1 for the binding of Cu(II) to hemoglobin. In other words, the rate of this reaction, which depends on the concentration of two reactants (hemoglobin and Cu(II)), is relatively high.
• Also, an apparent first-order rate for the reduction of Cu(II) to Cu(I) is stated to be at 0.051 s-1. A first-order reaction solely depends on the concentration of one reactant. In this case, it’s the transformation of Cu(II) into Cu(I).

The Role of Conformational Changes

• The research also indicates that the binding of Cu(II) to hemoglobin causes a noticeable alteration to the Cu(II) spectrum, decreasing the g values, which is related to the magnetic and electronic properties of a substance. An apparent rate constant of 17 s-1 is associated with this process.
• This alteration is thought to be a result of a conformational change in the region of the copper binding site. This refers to the change in the physical arrangement or structure of the protein hemoglobin when copper is bound to it.
• Such a conformational change is deemed necessary for Cu(II) to successfully carry out the oxidation of hemoglobin, thus highlighting the importance of this structural transition.