Electron migration in hydrated DNA and collagen at low temperatures. Part 2.—The effect of additives

Abstract

The effects of various additives on the transient conductivity signals seen on pulse irradiation of hydrated DNA and collagen have been investigated over the temperature range 135–250 K. The additives studied were ethanol, H₂O₂, NH₄F, HF, misonidazole and ethidium bromide with DNA and NH₄F with collagen. The observed reductions in signal height on addition of NH₄F or ethanol to the hydrated biopolymers were very similar to the reduction seen in the signal due to dry electrons in ice on addition of these impurities. However, ethidium bromide, which intercalates into the DNA helix, showed no measurable effect on the conductivity transients seen in the hydrated polymer. These observations strongly support the proposition that the signals observed on pulse radiolysis of hydrated DNA and collagen are due to the unsolvated electron migrating in an ice-like matrix around the biopolymer.