LAUSR

We investigate the effect of small organic cosolutes on local water structure and dynamics by means of Molecular Dynamics simulations. To find features distinct to protein stabilizers as compared to denaturants, we investigate aqueous solutions of the osmolytes ectoine and trimethylamine N-oxide (TMAO) as well as of the denaturants urea and guanidinium chloride (GdmCl). For each cosolute, we assess its effects on the surrounding water by analyzing several structural and dynamic properties of the local hydrogen bond network, as well as collective changes in the water’s dielectric relaxation spectra. While the concentration-dependent changes in water structure induced by the different cosolutes provide no clear trend, we find that the stabilizing osmolytes severely slow down the collective modes of reorientational water dynamics, whereas the effects on dynamics caused by denaturants are comparatively small. Our results indicate that the discussion of possible kosmo- or chaotropic cosolute effects only in te...