Studies on the surface orientation of uracil, uridine, thymine and thymidine at the mercury electrode surface by electrocapillary measurements

Abstract

In living cells, nucleic acids come into contact with various types of boundaries. The interfacial situation in the living cell, however, is very complex and not easily adjustable. Thus, versatile models of the biological interface and more simple molecules than the macromolecules of DNA and RNA are needed to contribute to a deeper understanding of the general biophysicochemical behaviour of these substances at charged interfaces. Therefore the present work is focussed on the surface activity of some nucleic acid components. Surface activity and interfacial phenomena of some nucleosides and nucleotides at the mercury/solution interface have been studied by various authors in the past [l-12]. The potentialities of polarography and voltammetry to study the interfacial behaviour of these biological compounds at charged interfaces have been established recently [13-191. The adsorption and association of uracil, thymine and their nucleosides and nucleotides at the mercury surface has been investigated by differential capacitance and ac voltammetric measurements [8,9,18,19]. The adsorption of these compounds was shown and factors which govern the ability of such compounds to promote the surface reorientation process were elucidated. At pH 9.0 and 25 o C, thymidine and thymidine mononucleotides differ significantly from the nucleosides and mononucleotides of uracil, since they do not exhibit the surface reorientation effect at the mercury/solution interface [9]. Continuing our quantitative studies on the interfacial behaviour of nucleic acid components [ll-191, we were further interested in investigating the surface activity of uracil, uridine, thymine and thymidine by electrocapillary measurements in order to study the surface orientation process of the investigated compounds at pH 7.0, which corresponds to the pH of the living cell.