engleski

Electrochemical Behaviour of Mono- and Oligo- nucleotides. I. Effects of Charge and Configuration of Adenine Mononucleotides on Their Adsorption at the Mercury-Solution Interface

A systematic study of the adsorption and interfacial behaviour of the adenine mononucleotides (5'-AMP, 3'-AMP, cyclic 3', 5'- AMP, 5'-ADP and 5'-ATP) and adenosine for comparison at the HMDE has been carried out at pH 3.4 to 3.5. Thus, the N(1) of the adenine moiety is protonated to a major extent. The adsorption was followed by single sweep voltammetry (measurement of the time integral of the reduction peak of the adsorbed adenine moiety) and by a.c. voltammetry. The situation corresponding to a "dilute" adsorption layer existing at low bulk concentrations was studied for various degrees of coverage. The potential dependence of the coverage is of bell shaped type with an extended maximum region around the potential of electrocapillary maximum (ECM) of the blank. For the same bulk concentration the coverage decreases in the series AMP, ADP, ATP, i.e. with increasing negative charge of the nucleotide. Among the monophosphates the coverage decreases in the series 3'-AMP, 5'- AMP, cyclic 3', 5'-AMP. The variations are connected with the varying charge of the mononucleotides and with the possibilities for interactions with adjacent molecules in the adsorption layer. At elevated bulk concentrations above a threshold value, a substantial increase in coverage around ECM as due to strong interactions between the adsorbed base moieties, a rather compact film is formed.

adenine mononucleotides ; adenosine ; adsorption ; mercury electrode ; a.c. voltammetry ; single sweep voltammetry

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