TWO-DIMENSIONAL CONDENSATION OF NUCLEOBASES: A COMPARATIVE STUDY OF HALOGEN DERIVATIVES OF CYTOSINE
The high ability of self-association of nucleic acid components leads to a two-dimensional (2D) condensation at electrode surfaces. The driving force of the process resides in the intermolecular interactions, such as dispersion forces, hydrogen bonding or electrostatic interactions. In this study, the condensation of 5-halogen cytosine derivatives (5-fluorocytosine, 5-bromocytosine and 5-iodocytosine) at the hanging mercury drop electrode was investigated to evaluate the influence of the different types of intermolecular interactions in the phenomenon. All of these derivatives form 2D capacitance pits, but in distinct conditions of pH, concentrations and temperature. Dispersion forces are identified as the main contributor to the 2D condensation of 5-iodocytosine, while for 5-fluorocytosine this is hydrogen bonding in hemiprotonated dimers. The third derivative, 5-bromocytosine, is an intermediate case between the two formers.