Binding reactions examples

Values of /c2 and Kd for the reactions of the cycloamyloses with a variety of phenyl acetates are presented in Table IV. The rate constants are normalized in the fourth column of this table to show the maximum accelerations imposed by the cycloamyloses. These accelerations vary from 10% for p-f-butylphenyl acetate to 260-fold for m-f-butylphenyl acetate, again showing the clear specificity of the cycloamyloses for meta-substituted esters. Moreover, these data reveal that the rate accelerations and consequent specificity are unrelated to the strength of binding. For example, although p-nitrophenyl acetate forms a more stable complex with cyclohexa-amylose than does m-nitrophenyl acetate, the maximal rate acceleration, h/kan, is much greater for the meta isomer. 

As we look at some of the reactions of intermediary metabolism, we shall rationahze them in terms of the chemistry that is taking place. In general, we shall not consider here the involvement of the enzyme itself, the binding of substrates to the enzyme, or the role played by the enzyme s amino acid side-chains. In Chapter 13 we looked at specific examples where we know just how an enzyme is able to catalyse a reaction. Examples such as aldolase and those phosphate isomerase, enzymes of the glycolytic pathway, and citrate synthase from the Krebs cycle were considered in some detail. It may... 

Both unimolecular and bimolecular reactions are common throughout chemistry and biochemistry. Binding of a hormone to a reactor is a bimolecular process as is a substrate binding to an enzyme. Radioactive decay is often used as an example of a unimolecular reaction. However, this is a nuclear reaction rather than a chemical reaction. Examples of chemical unimolecular reactions would include isomerizations, decompositions, and dis-associations. See also Chemical Kinetics Elementary Reaction Unimolecular Bimolecular Transition-State Theory Elementary Reaction... 

In addition to structure control, metal ions can act as reactive centers of proteins or enzymes. The metals can not only bind reaction partners, their special reactivity can induce chemical reaction of the substrate. Very often different redox states of the metal ions play a crucial role in the specific chemistry of the metal. Non-redox-active enzymes, e.g. some hydrolytic enzymes, often react as a result of their Lewis-acid activity [2], Binding of substrates is, however, important not only for their chemical modification but also for their transport. Oxygen transport by hemoglobin is an important example of this [3]. 

The determination of the quantity of protein bound to the insoluble carrier sometimes causes difficulties. The methods usually applied are laborious or somewhat inaccurate. Labeling of assayed protein, for instance with C-acet-anhydride, makes it possible to carry out a very fast and exact determination of immobilized protein The determination of bound enzyme C-labeled aldolase after its immobilization on polyacrylamide can serve as an example The concentration measurements of certain proteins are based on their ability to bind certain ligands. Radiolabels such as or H-biotin have been used for the determination of avidin by direct binding or for biotin assay by isotopic dilution Cofactor and fluorescent labeled ligands have been also used for the monitoring of specific protein binding reactions. 

In principle, electrochemical transducers can be used to detect the formation of a surface-bound affinity complex when the affinity-binding reaction is associated with a change in electrical properties (e.g., ion permeability or capacitance) of the layer immobilized onto the electrode surface. For example, the so-called ion-chemnel sensors detect permeabilily changes of a film immobilized on an electrode surface to an electroactive molecule, which is used as a redox marker. The formation of a surface-bound affinity complex results in a permeability change, which can be monitored by the change of cyclic voltammetric response of the redox marker. 

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