Concentration-binding curves

In overweight adults, a diabetic metabolic condition may develop (type II or non-insuUn-dependent diabetes) when there is a relative insulin deficiency-enhanced demand cannot be met by a diminishing insulin secretion. The cause of increased insulin requirement is a loss of insulin receptors or an impairment of the signal cascade activated by the insulin receptor. Accordingly, insulin sensitivity of cells declines. This can be illustrated by comparing concentration-binding curves in cells from normal and obese individuals... 

Figure 2 The dependence of O2 binding on Hb concentration. Binding curves are shown (solid black lines) for Hb concentrations of 0.005, 0.04, 0.10, 0.27,1.0, 5.4, and 38 pM (from left to right). Theoretical binding curves (broken red lines) are shown for a pure tetramer solution and a pure dimer solution. The macroscopic, thermodynamic linkage scheme relates the dimer tetramer assembly constants to the O2 binding constants for free dimer and assembled tetramer. The brackets around figurines indicate that the O2 ligand may be bound at any one of the available deoxy hemesites. Thus, the macroscopic constants are average values for multiple microscopic processes.

DIRECTIONS (Items 13-15) Each of the curves in the graph below may be considered a concentration-cffcct curve or a concentration-binding curve. For each numbered item, select the ONE lettered option that is most closely associated with it. 

Dmg distribution into tissue reservoirs depends on the physicochemical properties of the dmg. Tissue reservoirs include fat, bone, and the principal body organs. Access of dmgs to these reservoirs depends on partition coefficient, charge or degree of ionization at physiological pH, and extent of protein binding. Thus, lipophilic molecules accumulate in fat reservoirs and this accumulation can alter considerably both the duration and the concentration—response curves of dmg action. Some dmgs may accumulate selectively in defined tissues, for example, the tetracycline antibiotics in bone (see Antibiotics,tetracyclines). 

As discussed in Chapter 7, antagonists may bind to a separate loci on the receptor and thereby allosterically modify the affinity of the receptor for the agonist. The maximal change in the agonist affinity is denoted by a term a. It is useful to distinguish allosteric effects in terms of whether the modulator affects signaling and affinity or just affinity. In the latter situation, the modulator produces parallel shifts to the right of the concentration response curve up to a maximal point. This is discussed in Section 7.4.1 (t, = 1). Under these circumstances, the curve for... 

Figure 9 summarizes the electrode responses toward a variety of DNA-binding substrates [14c]. For intercalators (quinacrine, acridine orange, and safranin) and groove binders (spermine and spermidine), a steep rise followed by a saturation of the concentration response curve is commonly observed. If one compares the specific concentration which gives a 50% response in the increment of the cathodic peak current (A/p ) for each substrate, a selectivity order of quinacrine acridine orange > spermine > spermidine > safranin can be estimated. The binding constants measured in aqueous media for the affinity reaction with ds DNA are as follows quinacrine, 1.5 x 10 (38 mM NaCl)... 

Fig. 2. Competition binding screens Examples of concentration-response curves for 125I-CCL1 binding to human CCR8. U87 cells expressing hCCR8 were incubated with trace amounts of 125I-CCL1 (lOOpM) and increasing concentrations of cold CCL1 (circles) or compound A (squares).

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