Binding of solvent molecules

Mattos and Ringe have analyzed protein surfaces [53], reviewed proteins in organic solvents [54], and discussed the use of such information in inhibitor design [55]. 

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Solvents can act as inhibitors of enzymes and thereby decrease their activity. At least in some cases the inhibition is competitive and due to binding of solvent molecules in the active site of the enzyme. 

The structure of lipases has been shown to be similar in both water and hydrophobic solvents and binding of solvent molecules other than water has been observed. Rates of reaction and enantioselectivity have been altered by changing the solvent in a process called solvent engineering. 

For a substance to dissolve in a liquid, it must be capable of disrupting the solvent structure and permit the bonding of solvent molecules to the solute or its component ions. The forces binding the ions, atoms or molecules in the lattice oppose the tendency of a crystalline solid to enter solution. The solubility of a solid is thus determined by the resultant of these opposing effects. The solubility of a solute in a given solvent is defined as the concentration of that solute in its saturated solution. A saturated solution is one that is in equilibrium with excess solute present. The solution is still referred to as saturated, even... 

In coordinating solvents, such as MeCN and dmso, [Cu(dpa)2]2+ binds two solvent molecules becoming hexacoordinate. In contrast in non-coordinating solvents the complex maintains its tetracoordination. Figure 118 just shows the redox behaviour of the complex in noncoordinating nitromethane solution.175... 

Sharma and Reed, 1976)]. In proteins the coordination number 4 is most common, where the zinc ion is typically coordinated in tetrahedral or distorted tetrahedral fashion. The coordination polyhedron of structural zinc is dominated by cysteine thiolates, and the metal ion is typically sequestered from solvent by its molecular environment the coordination polyhedron of catalytic zinc is dominated by histidine ligands, and the metal ion is exposed to bulk solvent and typically binds a solvent molecule (Vallee and Auld, 1990). The inner-sphere coordination number of catalytic zinc may increase to 5 during the course of enzymatic turnover, and several five-coordinate zinc enzyme—substrate, enzyme product, and enzyme-inhibitor complexes have been studied by high-resolution X-ray crystallographic methods (reviewed by Matthews, 1988 Christianson and Lipscomb, 1989). The coordination polyhedron of zinc in five coordinate examples may tend toward either trigonal bipyramid or octahedral-minus-one geometry. 

A. H. Zewail My answer to Prof. Troe is that, in our experiment, already the cluster with one solvent shows the shift in 0- As for the boiling off of solvent molecules in larger clusters this is a nontrivial problem that we have considered in our paper. Based on the analysis of the translational eneigy and the kinetics, we concluded that the exponential decays (rates) are determined by the isomerization [see Chem. Phys. Lett. 242, 380 (1995)]. In any event, only one solvent molecule (at most) can be evaporated for the available energy studied experimentally recall that the binding energy of hexane is relatively large. 

The preferential interaction is, therefore, an expression of the affinity of one component for another in the most general sense, and while the term preferential binding is frequently used to express this effect, binding in this context in no way indicates immobilization of solvent molecules at... 

In summarizing their recent research, Karplus (Harvard University) and McCammon (University of Houston) observe that, from future research, much will be learned regarding how to calculate the rates of enzymatic reactions, and the binding of small molecules to large ones, as well as the role of flexibility and fluctuations in the function of macromolecules, For example, it should become possible to determine how particular solvent... 

In addition to maximizing contact area, inclusion also leads to more or less complete solvent exclusion from the receptor site, thus minimizing the number of solvent molecules to be displaced by the substrate on binding. 

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