PROTEIN-NUCLEIC ACID RECOGNITION - SIMULATION OF BASE AND MODEL AMINO-ACIDS COMPLEXES IN DMSO BY THE MONTE-CARLO METHOD

A computer simulation of guanine (G), cytosine (C), the G-C base pair, protonated C (CH+), acetic acid in neutral (AcOH) and deprotonated (A cO-) forms, G-AcO-, C-AcOH, and CH+-AcO- complexes, solvated in DMSO w as carried out by the Monte Carlo method. It is shown that the G-C bas e pair formation in DMSO is energetically favorable. The G-AcO- comple x formation is comparable with the formation of G-C base pair in energ etical favorability. In this case the acetate anion can replace C in t he G-C base pair. The formation of the C-AcOH complex is much less fav orable than the formation of the G-C pair. However proton transfer fro m AcOH to C leads to the formation of the CH+-AcO- complex, which is t he most favorable of all complexes studied. Here the acetic acid can r eplace G in a G-C base pair. The formation of G-AcO- and CH+-AcO- spec ific complexes detected in DMSO with the help of experiment and theory is a competitive process with respect to the formation of G-C base pa irs, and can be considered the primary step in the real mechanism of p rotein-nucleic acid recognition.