MONTE-CARLO SIMULATIONS ON THE LIKE-CHARGED GUANIDINIUM GUANIDINIUM ION-PAIR IN WATER

Monte Carlo simulations using the statistical perturbation theory were carried out for the guanidinium-guanidinium ion pair in water at 25°C and 1 atm using the isothermal-isobaric (NPT) ensemble to obtain interionic potentials of mean force and to evaluate "effective" interactions in water at short distances. The system is found to be attractive with a deep and large minimum at a C⋯C distance of approximately 3.30 Å. Our results address fundamental questions about interionic interactions in recognition processes involving like-charged binding sites. Contrary to the simple electrostatic picture, they may attract locally due to related induced solvent effects. © 1990 American Chemical Society.