Enzymes solvents

Entry Carboxy terminal Amino terminal Product Enzyme Solvent Yield, % Refs... 

Quantum mechanics is essential for studying enzymatic processes [1-3]. Depending on the specific problem of interest, there are different requirements on the level of theory used and the scale of treatment involved. This ranges from the simplest cluster representation of the active site, modeled by the most accurate quantum chemical methods, to a hybrid description of the biomacromolecular catalyst by quantum mechanics and molecular mechanics (QM/MM) [1], to the full treatment of the entire enzyme-solvent system by a fully quantum-mechanical force field [4-8], In addition, the time-evolution of the macromolecular system can be modeled purely by classical mechanics in molecular dynamicssimulations, whereas the explicit incorporation... 

In the absence of definitive information about the structure of the active site theoretical modeling of enzyme catalyzed reactions is difficult but not impossible. These difficulties are caused by the extremely large size of the enzyme-substrate-solvent system which typically comprises thousands or tens of thousands of atoms so that direct theoretical treatment at the microscopic quantum mechanical level is not yet practical. The computational demand is simply too enormous. As a compromise, a scheme generally referred to as QM/MM (quantum mechanics/molecular mechanics) has been devised. In QM/MM calculations, the bulk of the enzyme-solvent system (i.e. most of the atoms) is treated at a low cost, usually at the molecular mechanics (MM) level, while the more nearly correct and much more expensive quantum level (QM) computation is applied only to the reaction center (active site). 

Aliphatic ethers with branched side chains such as MTBE (methyl t-butyl ether), especially, deactivate enzymes only to a very small degree in incubation experiments for example, the BAL mentioned above has a half-life h/2 of up to 500 h in aqueous-organic two-phase systems (see Fig. 3.1.6) [21]. This may not hold true for a special enzyme/solvent combination under process conditions. When incubated at higher temperatures or even in the presence of the substrate benzaldehyde the deactivation of the enzyme is much higher (see Table 3.1.2)... 

Reaction engineering helps in characterization and application of chemical and biological catalysts. Both types of catalyst can be retained in membrane reactors, resulting in a significant reduction of the product-specific catalyst consumption. The application of membrane reactors allows the use of non-immobilized biocatalysts with high volumetric productivities. Biocatalysts can also be immobilized in the aqueous phase of an aqueous-organic two-phase system. Here the choice of the enzyme-solvent combination and the process parameters are crucial for a successful application. 

They showed that despite the fact that lower activities were generally observed, significant improvements of enantioselectivity in the oxidation of thioanisole by PAMO and EtaA could be induced by the addition of short-chain alcohols such as methanol and ethanol. Remarkably, methanol was able to cause a reversal of PAMO enantiopreference in the case of several substrates. Reversal of enantio-preference was also observed with EtaA when using t-BuOMe. The authors hypothesize that in these enzymes solvents exert their influence on enantioselectivity by binding in or near the enzyme active site and, depending on their structure, interfere with the association of the substrate. 

Fregapane, G., Sarney, D. B., and Vulfson, E. N., Enzymic solvent-free synthesis of sugar acetal fatty acid esters. Enzyme Microb. Technol., 13, 796-800, 1991. 

Compound No. Structure Enzyme Solvent Position Yield (%) Ref. 

Eerrer P, Montesinos JL, Valero E et al. (2001) Production of native and recombinant lipases by Candida rugosa a review. Appl Biochem Biotechnol 95 221—255 Fregapane G, Samey DB, Vulfson EN (1991) Enzymic solvent-free synthesis of sugar acetal fatty acid esters. Enzyme Microb Technol 13(10) 796-800 Fuenzalida M, Markovits A, Martinez I (2006) Process for producing sterol or stand esters by enzymatic transesterification in solvent and water free media. EP 1285969 Bl. Issued on November 10, 2006... 

Ionic Liquids and Enzymes Solvent Properties of Ionic Liquids... 

For enzymes (natural catalysts), researchers proposed " joining the quantum and the classical descriptions by making the precision of the description dependent on how far the region of focus is from the enzyme active center (where the reaction the enzyme facilitates takes place). They proposed dividing the system (enzyme + solvent) into three regions ... 

R Initial Yield [%) Intial ee(%) Enzyme Solvent Temp ( C) Conversion (%) Recovery %) Final ee(%)... 

Willstatter expressed his mature conclusions at Cornell University in 1926, and in the same place on 29 April of that year, J. B. Sumner obtained from jack bean a new protein that crystallizes beautifully and whose solutions possess to an extraordinary degree the ability to decompose urea to ammonium carbonate. Sumner marshaled arguments that his octahedral crystals were practically uncontaminated with any other material. Solutions of the crystals exhibited greater urease activity per unit weight than any other preparation of the enzyme. Solvents that did not dissolve the crystals had little or no urease activity. The crystals were proteins by every test, and in solution urease activity behaved like a protein in its reactions with heavy metals, alkaloid reagents, alcohol, and acids. 

Product Reactants Leaving Group Enzyme Solvent Other Aids Yield... 

Method Enzyme Solvent Purity of sTAG (%, w/w) Yield (%, w/w) References... 

The component that holds the stick together is sodium stearate. Other ingredients incorporated into the formulation are enzymes, solvents, surfactants, and water. 

Furthermore, no extensive reference library exists for enzymatic materials. It is critical, therefore, to design an experiment such that individual constituents of the biocomposite, such as dry enzymes, solvent-cast enzymes, substrates, and polymers, are aU analyzed to provide appropriate reference spectra. The respective widths and positions of peaks in the reference spectra can then be applied as constraints in curve fitting the spectra of the eomposite samples (enzyme encapsulated in matrix, layer-by-layer systems, etc.). Identification of species must be then cross-correlated and confirmed by spectra of all the elements that take part in the suspected type of chemical bond formation— for example, peaks due to C—N=0 must be confirmed by C Is, O Is, and N Is signals. 

Entry Substrate Product Enzyme Solvent Tield (%)... 

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