Thermoelectric effects and dielectric polarisation in biopolymers

Abstract

Seebeck coefficients show “dry” compressed discs of haemoglobin and NaDNA to be p-type, adsorption of water causing a change to n-type behaviour. The magnitude of the effect suggests that simultaneous thermodiffusion of adsorbed water may occur so as to magnify the changes in Seebeck coefficient with hydration for haemoglobin.

Step function d.c. transients applied to compressed discs of dry haemoglobin reveal two relaxations, designated α for the higher frequencies and Ω for the lower frequencies. The α peak is attributed to a Maxwell–Wagner interfacial polarisation, involving trapping of holes at defects in the compressed discs and the Ω peak to a polarisation at the electrode–semiconductor interface. An alternative explanation relating the α peak to dipolar orientation is also considered.

The possibility is discussed that the charge carriers are electrons and holes arising from a charge transfer within the protein, as earlier postulated for NaDNA.