Protein Dynamics as a Function of Hydration

Proteins in the dry state are frozen. They only open up and start moving if some water is added, as in nature. It turns out that protein movements in, e.g., lysozyme are activated only when there is 0.15 g of water per gram of protein, a good example of the effect of hydration on living processes. However, it is difficult to examine protein dynamics in solution because to make a satisfactory interpretation of the observations, one would have first to do the corresponding spectroscopy in the dry state this is difficult because of the frozen state referred to and a tendency to decompose. 

To avoid this difficulty, one technique is to use reverse micelles. These materials can host a protein in a small water pool. Reverse micelles are spherical aggregates formed by dissolving amphiphiles in organic solvents. The polar head of the amphiphilic molecule is in the interior of the aggregate and the hydrophobic tail is in the organic phase. The micellar suspension is transparent, and controlled amounts of water can be added. 

Protein Cuneentration Range (mg/ml) toiai (Ihers/protein) 

Source Reprinted from M. Suzuki, J. Shigematsu, and T. Kodama, Fkys. Chem. 100 7282, 1996. 

One can then use the time course of the fluorescence decay. The change in frequency of the emitted light compared with that of the incident light contains information from which the rotational and internal dynamics can be studied. 

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Protein dynamics, as a function of hydration, 191 Raman spectroscopy, and electrolytic solutions. 

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