Chemistry Reference
In-Depth Information
0
BSA-Water
-100
-200
BSA-PEG
-300
0
5000
10000
15000
Preferential Hydration (mol/mol)
FIGURE 11.10
Kirkwood- Buff integrals,
G
21
(diamond) and
G
23
(square), of bovine serum
albumin in the presence of the Hofmeister salts (filled) and PEGs (open). (Adapted from
S. Shimizu and N. Matubayasi, 2006, Preferential Hydration of Proteins: A Kirkwood-Buff
Approach,
Chemical Physics Letters,
420, 518.)
Here, again, the protein-cosolvent interaction has been shown to be a crucial
driving force describing the observed diversity of the cosolvent effect (Shimizu,
McLaren, and Matubayasi 2006).
11.7 CONCLUSIONS
I have demonstrated with examples that FST is indispensable in modern biochemistry
and biophysics. Not only has it provided a theoretical framework for the interaction
between biomolecules and the surrounding solvent molecules, but also a powerful
method for interpreting traditional and well-established thermodynamic data at a
molecular basis. This is in stark contrast with the pre-FST approaches, whose theo-
retical foundations were at best simple solvent binding and stoichiometric binding
models, which have been subject to unrealistic assumptions regarding the nature of
solvation. An FST-based reinterpretation of the classical experiments has confirmed
that it is the protein-cosolvent interactions, as well as its chemical variation, that
gives rise to a wide range of cosolvent actions (Figure 11.11). This picture has uni-
fied the phenomena that have hitherto been classified under a number of different
headlines—crowding, denaturation, Hofmeister effect,
m
-values, osmolyte effects,
to name but a few. FST-based analyses have also shown that the contribution from
the change in protein-water interactions is secondary. The precise molecular mecha-
nism that determines protein-cosolvent interactions in various solutions, of course,
still awaits fuller elucidation. More complete, molecular-based models, as well as the
incorporation of more solvent components, are amongst the most fruitful potential
developments (Pierce et al. 2008; Ploetz and Smith 2011a).
