Structure
and dynamics of biomolecules in non-aqueous ionic solutions
Babak Minofar
The Institute
of Nanobiology and Structural Biology, Academy of Sciences of the Czech Republic, Zamek
136, 37333 Nove Hrady,
Czech Republic
Biomolecules
such as enzymes can be solvated in organic solvents and ionic liquids, leading
either to conformational changes in their enzyme structure, or changes in their
enzymatic activity. The use of enzymes in organic media can bring benefits for
pharmaceutical industries by exploiting its potential for the asymmetric
synthesis of drugs because a majority of these compounds are insoluble in water
and organic solvent can improve their solubilities. Although organic solvents
and ionic liquids can improve the solubility of such non-soluble compounds,
solutions containing organic solvents can not be used at all concentrations for
enzymatic reactions thus limiting the usage of organic solvents in industrial
applications. Non aqueous solutions are not only changing the native structure
of enzymes or their catalytic activity, but they may lead even to denaturation
of biomolecules. In order to understand the solvation structure of biomolecules
in non-aqueous media and ionic liquids surface structure and bulk properties of
them must be studied both experimentally and theoretically.
Surface and bulk properties of such non-aqueous media can be studied by different experimental methods such vibrational sum frequency generation (VSFG) spectroscopy, second harmonic spectroscopy as surface sensitive methods and X-ray and neutron diffraction methods as techniques to study bulk properties. As theoretical method, classical molecular dynamics (MD) simulations have been used to study both bulk and surface properties of pure non-aqueous media and aqueous solutions of organic solvents and ionic liquids.
Due
to special properties of ionic liquids such as low vapor pressure, high thermal
stability, electrochemical stability and low volatility they can serve as
better solvents than usual organic solvents.
Non-aqueous media can have different effect of
the catalytic reaction such as lowering the energy of activated complex or
stabilization of enzyme in solution. Also using solution of organic solvents
can improve the solubility of some reactant and stabilize the structure of
biomolecules both by hydrophobic interactions and hydrogen bonding.
In this talk surface and bulk properties
of some protic and aprotic ionic liquids will be presented both theoretically
and experimentally. Moreover, the structure and dynamics of model protein in
non-aqueous media such as pure and aqueous solution of protic ionic liquid
which is studied by means of classical molecular dynamics (MD)simulations will
be presented.