ASES

Enzymes are classified in terms of the reactions which they catalyse and were formerly named by adding the suffix ase to the substrate or to the process of the reaction. In order to clarify the confusing nomenclature a system has been developed by the International Union of Biochemistry and the International Union of Pure and Applied Chemistry (see Enzyme Nomenclature , Elsevier, 1973). The enzymes are classified into divisions based on the type of reaction catalysed and the particular substrate. The suffix ase is retained and recommended trivial names and systematic names for classification are usually given when quoting a particular enzyme. Any one particular enzyme has a specific code number based upon the new classification. 

Hydrolases. Enzymes catalysing the hydrolytic cleavage ofC —O, C —N and C —C bonds. The systematic name always includes hydrolase but the recommended name is often formed by the addition of ase to the substrate. Examples are esterases, glucosidases, peptidases, proteinases, phospholipases. Other bonds may be cleaved besides those cited, e.g. during the action of sulphatases and phosphatases. 

Atoms Atoms are represented by their atomic symbols. The first letter is upperHydrogen atoms must be specified. 

Solvent-excluded surfaces correlate with the molecular or Connolly surfaces (there is some confusion in the literature). The definition simply proceeds from another point of view. In this c ase, one assumes to be inside a molecaile and examines how the molecule secs the surrounding solvent molecules. The surface where the probe sphere does not intersect the molecular volume is determined. Thus, the SES embodies the solvent-excluded volume, which is the sum of the van der Waals volume and the interstitial (re-entrant) volume (Figures 2-119. 2-120). 

In this ixpixsen talivc dihedral polenlial, V is the dihedral force con Sian L. n is th e periodicity of th e Fourier terni, Oo is th e ph ase angle, and t ) is ihe dihedral angle. 

The relative sizes ofthe poten tial barriers in dicate that the AF force con Stan t is larger th an the V con stan t. fh e ph ase sh ift is 180 degrees for th e Fourier compoiien t with a two-fold barrier. Minima occur at 180, 0, and I 80 degrees and maxima at 90 and 90... 

You usually rern ove restrain ts diirin g th e final ph ases of m olccti lar dynamics situ tilatious and gcom etry optimizations. 

Isolated gas ph ase molecules are th e sim plest to treat com pii tation -ally. Much, if not most, ch emistry lakes place in the liq iiid or solid state, however. To treat these condensed phases, you must simulate continnons, constant density, macroscopic conditions. The usual approach is to invoke periodic boundary conditions. These simulate a large system (order of 10" inoleeti les) as a contiruiotis replication in all direction s of a sm nII box, On ly th e m olceti Ics in the single small box are simulated and the other boxes arc just copies of the single box. 

Nomenclature. The compound on which the enzyme acts is known as the substrate. The name of the enzyme is now usually obtained by adding the termination ase to the name of the substrate. Thus an enzyme which hydrolyses an ester is known as an esterase. Nevertheless the older names of many enzymes still persist owing to their early disco ieiy. In some cases the name of the enzyme indicates the reaction w hich it catalyses, e.g. oxidase. 

Isomer 2,3,6-Isomer 2,3 Isomer 3,5 isomer Isomer ases Isomerization... 

S. Aureus Sausage Sausage casing Sausage casing material Sausages Sauter diameter Sauter mean diameter N.S. Savannah Savard-Lee injectors Savin ase... 

Chemical precipitation Chemical oxidation/re duction Air and/or steam stripping Activated carbon adsorption Resin adsorption Ion exchange Ultrafiltra-tion and/or reverse osmosis Flo atation / ph ase separation... 

To improve dimensional stabUity, low molecular weight chemicals are used that penetrate the cell waUs and either bond to the ceU waU polymers or polymerize in the ceU waU. Improvements in dimensional stabUity are measured by antishrink efficiency (ASE) ... 

ASE is a measure of the extent to which the swelling and shrinking tendency has been reduced at an equUibrium condition. 

It is possible to react an organic moiety to the hydroxyl groups on ceU waU components. This type of treatment also bulks the ceU with a permanently bonded chemical (68). Many compounds modify wood chemically. The best results are obtained by the hydroxyl groups of wood reacting under neutral or mildly alkaline conditions below 120°C. The chemical system used should be simple and must be capable of swelling the wood stmcture to facUitate penetration. The complete molecule must react quickly with wood components to yield stable chemical bonds while the treated wood retains the desirable properties of untreated wood. Anhydrides, epoxides, and isocyanates have ASE values of 60—75% at chemical weight gains of 20—30%. 

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