The Effect of Hofmeister Anions to Water

The effect of Hofmeister anions to water

network near protein surface

Euihyun Lee, Jun-Ho Choi, and Minhaeng Cho*

IBS CMSD Korea University

The water affects our life through strong interaction between water and other objects or themselves. We need to research for information of this water to understand and apply. Above all we have focused on the water in protein interface using MD simulation. Furthermore if ion is added in protein/water interface, then perturbation will be occurred or not. The H-bond number of water is standard which represents water network, already there are many researches about H-bond number along distance from hydrophobic surface such as protein1 and graphite2. We also observed phenomenon that decrease of H-bond number near protein surface. When the ion is added, there are no any specific ion effect in bulk region(5 Å~) that is far from protein surface. However the H-bond number decrease is occurred along ‘Hofmeister series’ which is related with solubility of protein near protein surface. We found the indirect reason of these properties, that is water network breaking by ion, not interaction between protein and ions. That also is found out the literature3 that study the effect of ion near protein surface using DSC(differential scanning calorimetry) and NMR. And we found the evidence that is related with order of Hofmeister series through ion distribution along the distance from protein surface.

Additionally, we investigated the number distribution and orientation distribution of each configuration of water to confirm preferential orientation at organic phase/water interface. Related researches are revealed experimentally using VSFS(vibrational sum frequency spectroscopy)4. Our results showed that the water has mainly random distribution, but slightly there are preferential configuration for straddle structure at protein/water interface.

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References

[1] N. Smolin, and R. Winter, “Molecular Dynamics Simulations of Staphylococcal Nuclease: Properties of Water at the Protein Surface”, J. Phys. Chem. B 2004, 108, 15928-15937.

[2] T. Werder, J. H. Walther, R. L. Jaffe, T. Halicioglu, and P. Koumoutsakos, “On the Water-Carbon Interaction for Use in Molecular Dynamics Simulations of Graphite and Carbon Nanotubes”, J. Phys. Chem. B 2003, 107, 1345-1352.

[3] J. W. Bye, N. J. Baxter, A. M. Hounslow, R. J. Falconer, and M. P. Williamson, “Molecular Mechanism for the Hofmeister Effect Derived from NMR and DSC Measurements on Barnase”, ACS Omega 2016, 1, 669-679.

[4] L. F. Scatena, M. G. Brown, and G. L. Richmod, “Water at Hydrophobic Surfaces: Weak Hydrogen Bonding and Strong Orientation Effects”, Science 2001, 292, 908-912.