A survey on the hofmeister effect of water
Date of Issue2016-05-25
School of Electrical and Electronic Engineering
In this paper, we present the latest progress in understanding the Hofmeister effect. To be specific, adding the salt into water, water molecules are adhered to a dissolved ion, forming a hydration shell. The hydration shell will be formed around the ionic protein molecules as well. Thus, adding the salt into aqueous solution, the number of free water molecules will be decreased, meanwhile it will also reduce the water molecules that could bond with protein molecules, result in changing the stability of protein. In water molecule, between two O2- atoms, there is repulsion force to keep them away from each other. Attraction forces could be found at both side of H+ atom which are the covalently bond and hydrogen bond. Thus make the atoms balanced. However, if we add salt into it, in water molecules, O-H stretching frequency increases by shorten the O-H bond. At the same time, the hydrogen band (O:H-O) frequency decreases then the band length will be extended. Then cause the distance between two O2- atoms lengthening, resulting in the repulsion force weakened. As we know from before, there is hydration shell in a solution. In the hydration shell, water molecules are bonded to the salt ions as H2O-Na+ and H2O-Cl-. Then replace the O2- atoms to Na+ ion or Cl- ion, we get the same effect of the repulsion force between ions.
Final Year Project (FYP)
Nanyang Technological University