Guanidinium carbonate was used in this study as a simple proxy for the biologically relevant 
arginine-carbonate interactions in water. Molecular dynamics (MD) simulations of guanidinium 
carbonate were performed with non-polarizible water using two implementations of the ion 
force fields.  In the first the ions had full charges, while in the second the ions had 
reduced charges in order to effectively account for electronic polarization effects of water. 
The results from the simulations were then compared to data from previous neutron scattering 
experiments.  It was found that there were significant discrepancies between the full charge 
force field MD simulations and the experimental results, due to excessive ion pairing and 
clustering in the former. In contrast, reducing the ionic charges yields a more regular 
solution with a simulated structure which fits well the experimental data.