https://zenodo.org/record/1258475/files/article.pdf

Electron transfers in chemistry and biology

A major portion of the toxicity of hydrogen peroxide in Escherichia coli is attributed to DNA damage mediated by a Fenton reaction that generates active forms of hydroxyl radicals from hydrogen peroxide, DNA-bound iron, and a constant source of reducing equivalents. Kinetic peculiarities of DNA damage production by hydrogen peroxide in vivo can be reproduced by including DNA in an in vitro Fenton reaction system in which iron catalyzes the univalent reduction of hydrogen peroxide by the reduced form of nicotinamide adenine dinucleotide (NADH). To minimize the toxicity of oxygen radicals, the cell utilizes scavengers of these radicals and DNA repair enzymes. On the basis of observations with the model system, it is proposed that the cell may also decrease such toxicity by diminishing available NAD(P)H and by utilizing oxygen itself to scavenge active free radicals into superoxide, which is then destroyed by superoxide dismutase.

https://science.sciencemag.org/content/sci/240/4857/1302.full.pdf

DNA damage and oxygen radical toxicity

Glutaraldehyde possesses unique characteristics that render it one of the most effective protein crosslinking reagents. It can be present in at least 13 different forms depending on solution conditions such as pH, concentration, temperature, etc. Substantial literature is found concerning the use of glutaraldehyde for protein immobilization, yet there is no agreement about the main reactive species that participates in the crosslinking process because monomeric and polymeric forms are in equilibrium. Glutaraldehyde may react with proteins by several means such as aldol condensation or Michael-type addition, and we show here 8 different reactions for various aqueous forms of this reagent. As a result of these discrepancies and the unique characteristics of each enzyme, crosslinking procedures using glutaraldehyde are largely developed through empirical observation. The choice of the enzyme-glutaraldehyde ratio, as well as their final concentration, is critical because insolubilization of the enzyme must result in minimal distortion of its structure in order to retain catalytic activity. The purpose of this paper is to give an overview of glutaraldehyde as a crosslinking reagent by describing its structure and chemical properties in aqueous solution in an attempt to explain its high reactivity toward proteins, particularly as applied to the production of insoluble enzymes.

https://www.future-science.com/doi/pdf/10.2144/04375RV01

Glutaraldehyde: behavior in aqueous solution, reaction with proteins, and application to enzyme crosslinking.

Oxidative stress responses in Escherichia coli and Salmonella typhimurium.

On the function and mechanism of action of peroxidases

The standard redox potential at I= 0.01, 25°C and pH 7.0 has been determined for the following species of cytochrome c: horse heart, baker's yeast isoenzyme-1, Candida species yeast, tuna heart and turkey heart. The thermodynamic parameters of the redox reaction were evaluated and found to be identical, within experimental error, in the five species investigated. The effect of pH on the standard redox potential of horse heart cytochrome c was studied in the pH range 7.0–11.2. A single heme-linked ionization of the oxidized protein was observed in this pH range, with a dissociation constant of 3 × 10−9 at I= 0 and 25°C. The effects of the electrostatic media on the standard redox potential of horse heart cytochrome c depend on the nature of the anions employed. For non-binding medium at 25°C, the observed potential dependence on the ionic strength is given by the equation: E0obs= 0.274–0.336 √I/(1 + 6√I). In binding medium, specific binding of ions to the protein takes place.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1432-1033.1973.tb02633.x

Cytochrome c: a thermodynamic study of the relationships among oxidation state, ion-binding and structural parameters. 1. The effects of temperature, pH and electrostatic media on the standard redox potential of cytochrome c.

The effects of alkylation of methionyl residues on the properties of horse cytochrome c.

Binding of hydrogen donors to horseradish peroxidase: A spectroscopic study

Cytochrome c: a thermodynamic study of relationships among oxidation state, ion-binding and structural parameters. 2. Ion-binding linked to oxidation state.

Abel Schejter

Papers

Cytochrome c: a thermodynamic study of the relationships among oxidation state, ion-binding and structural parameters. 1. The effects of temperature, pH and electrostatic media on the standard redox potential of cytochrome c.

The effects of alkylation of methionyl residues on the properties of horse cytochrome c.

Binding of hydrogen donors to horseradish peroxidase: A spectroscopic study

Cytochrome c: a thermodynamic study of relationships among oxidation state, ion-binding and structural parameters. 2. Ion-binding linked to oxidation state.

The reaction of cytochrome c with imidazole.