Electron migration in hydrated DNA and collagen at low temperatures. Part 1.—Effect of water concentration

Abstract

The migration of charges formed in hydrated DNA and collagen at low temperatures by nanosecond pulses of 3 MeV electrons has been studied by measuring the microwave conductivity on nanosecond and microsecond timescales. The radiation-induced conductivity is found to be critically dependent on the water concentration of the samples. No radiation induced conductivity could be detected below water concentrations of 0.41 and 0.79 gram water per gram dry collagen and DNA, respectively. Above the critical water concentration the conductivity increases approximately linearly with water concentration. It is suggested that the observed conductivity is due to a highly mobile ‘dry’ electron migrating in the ice-like water layer around the biopolymer, with a mobility similar to that of the excess electron in pure ice (2.5 × 10^–3 m² V^–1 s^–1) but with a considerably longer lifetime.