The structure, dynamics, hydration and enantioselective properties of proteins in nonaqueous solvents are here investigated using molecular modelling methods. This study has been carried using the model enzyme cutinase from Fusarium solani pisi. The nonaqueous solvents employed belong to two distinct classes: organic solvents (hexane, diisopropyl ether, 3-pentanone, ethanol and acetonitrile) and room temperature ionic liquids (RTILs) 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF₆]) and 1-butyl-3-methylimidazolium nitrate ([BMIM][NO₃]). The content of this thesis is contained in four publications [2,4,1,3] that correspond to sections 3, 4, 5 and 6 respectively.
  The first work presents an extensive study of a system composed by one enzyme solvated by different organic solvents, with increasing water content ranging from 5% to 100%  (w/w) (weight of water/weight of protein). Five organic solvents of increasing polarity were used: hexane, diisopropyl ether, 3-pentanone, ethanol and acetonitrile. We show that the overall enzyme structural properties are dependent on the water content and organic solvent. A more native like enzyme structure is observed at specific hydration conditions when low polar organic solvents are used. The enzyme is preferentially stabilized, as judged by the enzyme C-alpha root mean square (RMS) deviation against the X-ray structure, at a water content of 7.5% in hexane, 30% in diisopropy ether and 40% in 3-pentanone. A higher or lower amount of water from this optimum, leads to higher RMS deviations. This structural dependence with the amount of water resembles a bell-shape like behaviour. It is also shown that the different organic solvents strip water from the enzyme surface in different extents. Low polar organic solvents retain high amount of water at the enzyme surface while high polar organic solvents remove most of the water from the enzyme surface. It is also observed that in all organic solvents tested, water seems to be preferentially located at similar surface regions of the enzyme.
 In the same sense that the structural and dynamic properties of some enzymes are dependent on the hydration condition in a bell-shape behaviour, some enzymes also reveal that there is an optimum hydration condition that maximizes their native enantioselective properties. In a second study we describe a molecular modelling study regarding the enantioselective properties of our enzyme with different hydration conditions in hexane. We have addressed the preferential stabilization of the enzyme toward the tetrahedral intermediate of two enantiomeric substrates: (R/S)-1-phenyl ethanol (1PE) and (R/S)-2-phenyl-1-propanol (2P1P). We show that the R enantiomers are preferentially stabilized by the enzyme. We also present that low-water conditions enhance the enzyme preference toward the native favoured R enantiomer, being this preference maximized at 10% (w/w) water content. Some structural details of the active site that are correlated with the improved stabilization of the tetrahedral intermediate at low-water conditions are described in detail.
 The last two studies address the recent advances in the field of nonaqueous enzymology, that is, the use of RTILs as a media for enzyme catalyzed reactions. The third study is the development of a united-atom model parameterization of two RTILs compatible with the GROMOS 43A1 force field to be used in our protein molecular modelling studies, [BMIM][PF₆] and [BMIM][NO₃], which were not available in the literature. We developed a parameterization that was validated against known experimental properties, namely, density, self-diffusion and shear viscosity, within a temperature range of 298 to 363 K. After the development of these two RTILs parameterization we carried a comprehensive molecular modelling study (presented in a fourth study) addressing the structure, dynamics and hydration properties of our enzyme in these RTILs. Different enzyme hydration conditions and two temperatures, 298 and 343 K were simulated. We show that the enzyme is preferentially stabilized by [BMIM][PF₆]. We also show that the enzyme in [BMIM][PF₆] has a RMS deviation dependence with water content similar to a bell-shape profile, in the same way as previously observed in hexane. Water plays a fundamental role in promoting enzyme stability in this type of media. The enzyme in [BMIM][PF₆]  has a structure more native like in the presence of 5-10% water content. The enzyme is also show to be relatively stable at higher temperature in [BMIM][PF₆] at low water contents. On the other hand [BMIM][NO₃] has show to be a destabilizing medium for our enzyme in comparison to [BMIM][PF₆], as reported experimentally for other enzymes. Enzyme destabilization in this IL seems to be related to the strong interaction of the [NO₃]^- anion with the enzyme main chain.

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