Multiple binding functionality

Closer least-squares fits can obviously be obtained by adopting more complicated models involving extra parameters. The use of more complicated models can, of course, be more readily justified if there is independent supporting evidence available (e.g., knowledge of multiple binding sites from functional studies). 

Except for very simple systems, initial rate experiments of enzyme-catalyzed reactions are typically run in which the initial velocity is measured at a number of substrate concentrations while keeping all of the other components of the reaction mixture constant. The set of experiments is run again a number of times (typically, at least five) in which the concentration of one of those other components of the reaction mixture has been changed. When the initial rate data is plotted in a linear format (for example, in a double-reciprocal plot, 1/v vx. 1/[S]), a series of lines are obtained, each associated with a different concentration of the other component (for example, another substrate in a multisubstrate reaction, one of the products, an inhibitor or other effector, etc.). The slopes of each of these lines are replotted as a function of the concentration of the other component (e.g., slope vx. [other substrate] in a multisubstrate reaction slope vx. 1/[inhibitor] in an inhibition study etc.). Similar replots may be made with the vertical intercepts of the primary plots. The new slopes, vertical intercepts, and horizontal intercepts of these replots can provide estimates of the kinetic parameters for the system under study. In addition, linearity (or lack of) is a good check on whether the experimental protocols have valid steady-state conditions. Nonlinearity in replot data can often indicate cooperative events, slow binding steps, multiple binding, etc. 

For enhancement of fluorescence, molecules with intramolecular fluorescence quenching of photoinduced electron transfer (PET) of lone pairs are used. When interacting with the target molecule, this quenching will be inhibited and therefore the fluorescence can be turned on. The l,T-binaphthyl macrocycles are most extensively applied for this method they provide multiple chiral functional groups as binding sites for analytes such as a-hydroxycarboxylic acids, amines and even amino acid derivatives [5] (Fig. 3, left). 

The chief function of lectins in animals is to facilitate cell-cell contact. A lectin usually contains two or more binding sites for carbohydrate units some lectins form oligomeric structures with multiple binding sites. The binding sites of lectins on the surface of one cell interact with arrays of carbohydrates displayed on the surface of another cell. Lectins and carbohydrates are linked by a number of relatively weak interactions that ensure specificity yet permit unlinking as needed. The interactions between one cell surface with carbohydrates and another with lectins resemble the action of Velcro each interaction is relatively weak but the composite is strong. 

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