Binding, complex/kinetics

MS is lower than that of M the system is in the regime of substrate saturation addition of more S does not lead to a rate increase. The behaviour of the reaction rate in case B is typical of enzymes and in biochemistry this is referred to as Michaelis-Menten kinetics. The success of the application of the Michaelis-Menten kinetics in biochemistry is based on the fact that indeed only two reactions are involved the complexation of the substrate in the pocket of the enzyme and the actual conversion of the substrate. Usually the exchange of the substrate in the binding pocket is very fast and thus we can ignore the term k2[H2] in the denominator. Complications arise if the product binds to the binding site of the enzyme, product inhibition, and more complex kinetics result. 

Interactions between small molecules and HRP are an important source of information about structure and reactivity at the heme group and its immediate environment. Several reviews are available in which ligand binding, and kinetic and spectroscopic characterization of the complexes are described (predominantly for HRP C rather than for other isoenzymes) (8, 23, 24). HRP ligands can be broadly classified into two groups on the basis of whether they bind to the vacant sixth coordination site of heme iron or not. Certain species such as iodide and... 

Measurement of the extent to which the adsorbent removes the adsorbate from a liquid or gaseous phase. The data is used to construct adsorption isotherms and is often fitted to a model to provide information about binding constants, adsorption maxima and other parameters, and also speciation of surface complexes. Kinetic data may also be obtained. 

If two different substrates bind simultaneously to the active site, then the standard Michaelis-Menten equations and competitive inhibition kinetics do not apply. Instead it is necessary to base the kinetic analyses on a more complex kinetic scheme. The scheme in Figure 6 is a simplified representation of a substrate and an effector binding to an enzyme, with the assumption that product release is fast. In Figure 6, S is the substrate and B is the effector molecule. Product can be formed from both the ES and ESB complexes. If the rates of product formation are slow relative to the binding equilibrium, we can consider each substrate independently (i.e., we do not include the formation of the effector metabolites from EB and ESB in the kinetic derivations). This results in the following relatively simple equation for the velocity ... 

Ligand- macromolecule complex Stoichiometry of complex Kinetics of binding Location of interacting sites Orientation of bound ligand Structure of complex Dynamics of complex Chemical shift titration Line width, titration analysis HSQC, isotope editing NOE docking 3D/4D NMR Relaxation time measurements... 

Most of our early work in this area centered on the complexes Ru(tpy)(L)OH22+, where L = bpy, phen, and dppz (Figure 1, tpy = 2,2, 2"-terpyridine) (7, 30, 33). These complexes cleave DNA upon oxidation to Ru(tpy)(L)OH2+ and Ru(tpy)(L)02+, which can be performed chemically or electrochemically. We have a number of other complexes in our laboratory with similar properties (39) however, we will begin here with a discussion of the binding and kinetics of the simple, achiral tpy complexes, which have provided a basis for the design of cleavage agents with other desirable properties. 

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