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Electrochemical behaviour of mono- and oligonucleotides: Part III. Adsorption parameters of the dilute and compact adsorption layer of adenosine and adenine mononucleotide

Extended systematic studies on the adsorption of protonated adenosine and adenine mononucleotides by the joint application of the small amplitude method out-of-phase a.c.voltammetry and the large amplitude method rapid single sweep voltammetry have established the data for the quantitative elucidation of the interfacial behaviour of these substances of particular biological significance. Over a wide potential range one has a dilute adsorption layer while within the potential range of maximum adsorption at elevated bulk concentrations formation of a compact film is observed. The adsorption can be described quantitatively for both types of adsorption layers by a single and double step Frumkin isotherms, respectively. The resulting adsorption parameters are evaluated and the conclusions on the respective interfacial behaviours, orientations and interactions of these substances are summarized and compared with their corresponding interfacial behaviour when they are integrated as building stones in oligo- and polynucleotides and DNA. Moreover, the adsorption parameters of adenosine typical for a purine type nucleoside are compared with those of cytidine typical for pyrimidine nucleosides. In general methodological sense the study is a good example of the particular potentialities of the joint application of the two chosen voltammetric methods for the quantitative elucidation of the involved interfacial behaviour of strongly surface active substances which are able also to undergo electrochemical reduction or oxidation at certain potentials.

mononucleotides ; oligonucleotides ; adenine ; adenosine ; adsorption ; a.c. voltammetry ; single sweep voltammetry

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