Protein Solvation

For solvation of small molecules, the polarizable continuum model (PCM) and its variants have been widely used for calculation of solvation energy. The conductor-like PCM (CPCM) model gives a concise formulation of solvent effect, in which the solvent s response to the solute polarization is represented by the presence of induced surface charges distributed on the solute-solvent interface. In this formulation, no volume polarization (extension of solute s electron distribution into the solvent region) is allowed. The induced surface charge counterbalances the electrostatic potential on the interface generated by the solute molecule. 

By discretizing the induced charges on tesserae, the basic mathematics of CPCM is given by 

When the solute is relatively small, the number of surface tesserae is also small which makes direct matrix inversion of Eq. 10.7 feasible. The computational time and storage requirement for the direct inversion of matrix A is on the order of N, where N is the number of tesserae. For large solutes such as protein, the number of surface tesserae can be very large. Even the allocation for matrix A may cause memory overflow. Therefore iterative methods are required with on-the-fly calculations of the columns or rows of matrix A whenever necessary (Barrett et al., 1994). 

The calculated induced charge q in Eq. 10.7 is scaled for the finite dielectric constant correction by 

After convergence, the reaction field energy is calculated as 

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Paleg, L.G., Stewart, G.R. Bradbeer, J.W. (1984). Proline and glycine betaine influence protein solvation. Plant Physiology, 75, 974-8. 

Brass, O., J.M. Letoffe, A. Bakkali, J.C. Bureau, C. Corot, and P. Claudy. 1995. Involvement of protein solvation in the interaction between a contrast medium (iopamidol) and fibrinogen or lysozyme. Biophys Chem 54 83-94. 

Reduce water molecules available for protein solvation... 

Winzor, D.J., Carrington, L.E., Harding, S.E. (2001). Analysis of thermodynamic nonideality in terms of protein solvation. Biophysical Chemistry, 93, 231-240. 

The protein solvation, and the internal and surface hydrogen bond structure. 

Colombo ME, Rau DC, Parsegian VA. Protein solvation in allosteric regulation A water effect on hemoglobin. Science 1992 256 655-659. 

Addition of nonionic polymer PEG Very efficient for low-MW proteins like globulins it precipitates protein by effectively reducing the amount of water required for protein solvation... 

We end this long chapter with a brief discussion of a very important subject of intensive research. We present here only a few aspects of protein solvation. Since proteins do not have any measurable vapor pressure, their solvation Gibbs energy cannot be measured. It is also extremely difficult to compute it either theoretically or by simulation methods. However, owing to the utmost... 

Burling FT, Weis WI, Flaherty KM, Briinger AT Direet observation of protein solvation and discrete disorder with experimental crystallographic phase. Science 1996, 217 72-77. 

Osmolytes have also been employed to modulate the behavior of water molecules around the biomolecules in question, in order to understand protein hydration namely, the interaction between water and protein molecules (Parsegian, Rand, and Ran 1995). This is the area that was particularly controversial this has initially necessitated a rigorous molecular understanding of protein solvation in mixed solution. Therefore, 1 shall start this chapter from this topic, in order to show why fluctuation solution theory (FST) is indispensable for the understanding of bio-molecular solvation. 

Hu, C. Y, H. Kokubo, G. C. Lynch, D. W. Bolen, and B. M. Pettitt. 2010a. Backbone additivity in the transfer model of protein solvation. Protein Science. 19,1011. 

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