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FIGURE 8.11 Influence of a decreasing forward binding rate coefficient, fef, on the normalized antigen concentration in solution near the surface, cs/c0, when nonspecific binding is present for (a) a = 0.01 and (c) x = 0.1, and on the amount of antigen specifically bound to the antibody immobilized on the biosensor surface, r^g/c0, for a one-and-one-half-order reaction for (b) a = 0.01, and (d) a = 0.1.

Figures 8.12a-8.12d show the influence of a decreasing fef on the cs/c0 and the ryCo values when nonspecific binding is present for a second-order reaction. Figure 8.12a shows that for an a value of 0.01 an increase in the /? value leads to an increase in the cs/c0 value, as expected. When p — 0, the cs/c0 value decreases continuously. Similar behavior was observed for the one-and-one-half-order reaction. Note that for ¡3 > 0 the cs/c0 curve exhibits an initial decrease followed by an increase that asymptotically approaches a value of 1 for large time t. Similar behavior was observed for the one-and-one-half-order reaction for the same a value. Similarly, Fig. 8.12b shows that an increase in the /J value also leads to a decrease in the amount of antigen in solution bound specifically to the antibody immobilized on the surface. Once again (as observed for the one-and-one-half-order reaction), higher [i values also lead to lower rates of specific binding as well as lower levels of apparent saturation. Figure 8.12c shows that for an a value of 0.1 an increase in the [i value once again leads to an increase in the cs/c0 value, as expected. Figure 8.12d shows the complexities involved when a = 0.1 in the specific binding of

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2.4E-10 -2.2E-10 . 2.0E-10 1.8E-10 > 1.6E-10 ' »1.4&-10 " f ' 1.2E-10 ■ 1.0E-10 -8.0E-11 . 6.0E-11 4.0E-11 ' 2.0E-11 !

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FIGURE 8.12 Influence of a decreasing forward binding rate coefficient, kf on the normalized antigen concentration in solution near the surface, cs/c0 when nonspecific binding is present ((a) a = 0.01) and (c) a = 0.1), and on the amount of antigen bound specifically to the antibody immobilized on the biosensor surface, T^g/co for a second-order reaction for (b) a = 0.01, and (d) a = 0.1.

the antigen in solution to the antibody immobilized on the surface. There is an optimum value of /? that leads to the highest rate of specific binding as well as the amount of antigen bound specifically to the surface. Note that for a reaction time of 3 min the highest amount of T\g/co occurs at a /i value of 0.02, and the highest rate of specific binding occurs at a value of 0.01. The /? values are identical for the one-and-one-half- and second-order reactions as far as obtaining the highest r^g/c0 for this time interval.

Figures 8.13a and 8.13b show the influence of an increasing k¡ on the cs/c0 and the P4g/co values when nonspecific binding is present (a = 0.5) for a firstorder reaction. As expected, an increase in the ft value leads to a decrease in the cs/c0 value and a very slight (almost imperceptible) change in the Co value.

Figures 8.14a-8.14d show the influence of an increasing k¡ on the cs/c0 and the ry Co values when nonspecific binding is present for a one-and-one-half-order reaction. Figure 8.14a shows that for an a value of 0.01 an increase in

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