Hydration-activated

Table 3. Nmr Shifts and Hydration Activation Energies for Butylenes...

Kobayashi, E., Sugai, M., Imajyo, S., Adsorption of arsenate ion by the zirconium(iv) oxide hydrate active carbon complex. Nihon Kagaku Kaishi 1984, 656-660. 

The activity of polymer-supported crown ethers is a function of % RS as shown in Fig. 11 149). Rates for Br-I exchange reactions with catalysts 34, 35, and 41 decreased as % RS increased from 14-17% to 26-34%. Increased % RS increases the hydro-philitity of the catalysts, and the more hydrated active sites are less reactive. Less contribution of intraparticle diffusion to rate limitation was indicated by less particle size dependence of kohMi with the higher % RS catalysts149). 

The C02 hydration activity of cat isoenzyme III is independent of pH in the range of 5.0 < pH < 8.5 (148). The pKa value of zinc-H20 is outside this pH range and probably quite low due to electrostatic effects from positively charged active-site groups such as Lys-64 and Arg-67 (143). 

Khalifah, R. G. The carbon dioxide hydration activity of carbonic anhydrase. I. Stop-flow kinetic studies on the native human isoenzymes B and C. J. Biol. Chem. 246, 2561-2573(1971). 

A structure-function study of a proton pathway in the y-class carbonic anhydrase from Methanosarcina thermophila was conducted in the work of Tripp and Ferry (2000). Four enzyme glutamate residues were characterized by site-directed mutagenesis. It was shown that Glu 84 and an active site residue, Glu 89, are important for CO2 hydration activity, while external loop residues, Glu 88 and Glu 89 are less important. Glu 84 can be substituted for other ionizable residues with similar pKa values and, therefore, participates in the enzyme catalysis not as a chemical reagent but as a proton shuttle. 

Figure 5 Proposed acid/base catalytic interactions in the HDV ribozyme active site. The cleavage site for the HDV ribozyme is shown with the nucleotide 5 to the site of bond cleavage shown in red and the nucleotide 3 to that site shown in blue. Two proposed mechanisms for the function of the C76 cytisine nucleobase and a hydrated active site metal ion are shown in which C76 acts as either an acid (left) or base (right) as described in the text.

Adsorption is the adhesion of molecules of a gas, liquid, or dissolved substance or of particles to the surface of a solid substance. Absorption is the assimilation of molecule into a solid or liquid subsunce, with the formation of a solution or a compound. Sometimes the word sorption is used to indude both of these phenomena. We say that a heated glass vessel adsorbs water vapor from the air on cooling, and becomes coated with a very thin layer pf water a dehydrating agent such as concentrated sulfuric add absorbs water, forming hydrates. Activated alumina sorbs water vapor, probably both by adsorption (the adhesion of a layer of water vapor to the surface of rhe particles.) and by absorptimi (the formation ipf aluimnunt hydroxMe). 

Magnetics-activated drug delivery systems Sonophoresis-activated drug delivery systems Iontophoresis-activated drug delivery systems Hydration-activated drug delivery systems... 

Metal ionh) derivative Relative CO 2 hydration activity Relative rate of p-nitrophen-ylacetate hydrolysis... 

The strain DS5 system produced more keto product from palmitoleic and oleic acids and more hydroxy product from myristoleic, linoleic, and a- and y-linolenic acids. The reason for fliis preference is not clear. Among die 18-carbon unsaturated fatty acids, an additional double bond in either side of die C-10 position lowers the enzyme hydration activity. A hterature search revealed diat all microbial hydratases hydrate oleic and linoleic acids at the C-10 position (Fig. 2). Therefore, die positional specificity of microbial hydratases might be universal. 

Stretch activation of muscle is a well-described phenomenon it was the subject of The Croonian Lecture (1977) given by Pringle,and it has been extensively researched and reported in the literature over the ensuing decades. For example, the basic description becomes When active insect flight muscle is stretched, its ATPase rate increases.. . This we take as yet another demonstration of a fundamental process whereby a phosphate present in a protein can be activated, energized, as the result of an increase in hydrophobicity. It is an example of the competition for hydration between apolar and polar species, that is, an example of the apolar-polar repulsive free energy of hydration active in muscle contraction. 

Hydrodynamic-pressure-activated ° Hydration-activated o Vapor-pressure-activated ° Mechanically activated ° Magnetically activated ° Ultrasound-activated ° Electrically activated... 

A mixture of phenylacetic acid, a slight excess of hydrazine hydrate, activated alumina (Alcoa F-1), and 1-butanol heated with vigorous stirring in an oil bath at 140-150°, benzene added gradually to maintain a heavy reflux at 94-95° with water separation in a Dean-Stark apparatus, and the product isolated after 5 hrs. -> phenylacetyl hydrazide. Y 99%. — Alumina shows a remarkable catalytic activity promoting exclusively the formation of monoacylhydrazide. The catalyst permits lowering of the reaction temp, to a point where byproducts are no longer formed. The water produced must be continuously removed. F. e. s. T. Rabini and G. Vita, J. Org. Chem. 30, 2486 (1965). 

Addition of oxyhaemoglobin to CA causes a decrease in the CO2 selfexchange rate and an increase in the hydration activity measured by 0 tracer studies of exchange between CO2 molecules and COa/HjO respectively at 25 °C. This is explained in terms of proton transfer from Hb02 to the active CA site by way of a complex with a stability constant between 10 and 10 M . 

Polysilicic acid (oligomers). Polymers with molecular weights (as SiOj) up to about 100,000, whether consisting of highly hydrated active" silica or dense spherical particles less than about 50 A in diameter. 

Fig. 40. [Cu(F-pymo)2(H20) (H20)i 25] . (a) Temperature dependences of the magnetic susceptibilities and (b) fM7 product for as-synthesized hydrated, activated [Cu(F-pymo)2] , and loaded with CO2 (l -C02) [08N1].

The above discussion bears heavily on the analysis of the patterns of anionic inhibition of BCA catalysis. Anionic inhibitors, depending on the choice of pH and substrate, are able to inhibit solely through the apparent Km of HCOo dehydration activity largely through only the apparent ) of CO2 hydration activity... 

The individual Kj values in Scheme lean be determined as follows k is the Kfl term for anionic inhibition of CO2 hydration activity at limiting low pH. k is the term under the same conditions. 

The third case to be dealt with is kinetically the most involved the inhibition of CO2 hydration activity by HCO3. For the... 

A study of the anion inhibition of Cobalt(II) HCAC CO2 hydration activity reported a loss of inhibitory power of anions at high pH(21). Further scrutiny of the high pH anion inhibition of metal substituted carbonic anhydrase is certainly in order. If, as it appears, high pH anion activity inhibition is a property confined to the natural substrate of the Zinc(II) enzyme, the implications for conclusions drawn from studies of model substrates and metal substituted enzymes need to be carefully scrutinized. 

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