Kinetic behavior of the reaction between hydroxyl radical and the SV40 minichromosome

Abstract

Aqueous solutions containing the minichromosomal form of the virus SV40 and the radical scavenger DMSO were subjected to gamma-irradiation, and the resulting formation of single strand breaks (SSB) was quantified. Under the irradiation conditions, most SSBs were produced as a consequence of hydroxyl radical ( • OH) reactions. By controlling the competition between DMSO and the viral DNA substrate for • OH, we are able to estimate the rate coefficient for the reaction of • OH with the SV40 minichromosome. The results cannot be described adequately by homogeneous competition kinetics, but it is possible to describe the rate coefficient for the reaction as a function of the scavenging capacity of the solution. The experimentally determined rate coefficient lies in the range 1×10 9 -2×10 9 L mol −1 s −1 at 10 7 s −1 , and increases with increasing scavenging capacity.

Length and Time-Dependent Rates in Diffusion-Controlled Reactions with Conjugated Polymers

“…The actual conformations and dimensions may be less well-known in solution than in cells, but the overall length could be as large as 792 nm, which is substantially longer than the molecules studied here. For a 792 nm length, eq with average radii of 2−4 nm gives rate constants k inf = 1.4−1.6 × 10 12 M −1 s −1 , which is slower than the observed values . However, this discrepancy may be due to the time dependence.…”

“…Related ObserWations for Reaction of OH • radicals with DNA. Reactions of OH • radicals with varied forms of DNA have received attention 53,67,[69][70][71] because the effects of radiation on living cells including cell death and mutations are thought to arise principally from damage to DNA resulting from OH • attack. The largest rate constants were 10 9 -10 10 M -1 s -1 (per residue concentration) found for the SV40 minichromosome having 10 486 residues (bases).…”

“…69 However, this discrepancy may be due to the time dependence. Taking the average radius to be 3 nm and D ) D(OH • ) ) 2.8 × 10 -5 cm 2 /s, 72 application of eq 1 to include the time dependence predicts k(t) from 1.9-22 × 10 13 M -1 s -1 in reasonable accord with the observations of Ly et al 69 for their observation times from 500 to 3 ns. Equation 1predicts that for this very long molecule k(t) will approach k inf (within 10%) only for times of ∼50 ms.…”

“…For a 792 nm length, eq 5 with average radii of 2-4 nm gives rate constants k inf ) 1.4-1.6 × 10 12 M -1 s -1 , which is slower than the observed values. 69 However, this discrepancy may be due to the time dependence. Taking the average radius to be 3 nm and D ) D(OH • ) ) 2.8 × 10 -5 cm 2 /s, 72 application of eq 1 to include the time dependence predicts k(t) from 1.9-22 × 10 13 M -1 s -1 in reasonable accord with the observations of Ly et al 69 for their observation times from 500 to 3 ns.…”

Nanodosimetry-based quality factors for radiation protection in space

“…It is important to note that p sb is essentially a radiochemical parameter. Its value depends on the kinetics of the chemical reactions of the initial water radiolysis products (e.g., the hydroxyl radical) within the scavenging environment of the DNA [29]. The subsequent cascade of signaling and repair responses of cells, which is likely to be responsible for the large variations in intrinsic radiosensitivity, should not affect p sb .…”