Plotting 1/(A0-A) according to 1/[Dt] gives the binding constant
K according to the slope.
In this case, CH signals were used to calculate the binding constant
. However, for [I.sup.-], N[O.sub.3.sup.-] and Cl[O.sub.4.sup.-], a negligible change in the NMR signals was observed.
As the double reciprocal plot of 1/[DELTA]A versus 1/[L] is linear, the binding constant
can be estimated from the following equation:
The intrinsic binding constants
([K.sub.b]) were calculated at [[lambda].sub.max] for each charge transfer band; 364.7, 366.4, 365.1, and 458 nm attributing to the binding yields of silver complexes (1-4) and DNA.
where [[K.sub.a]] and [Q] are the total concentration of HSA and coumarin drug, respectively, and the binding constant
and number of binding sites were obtained and tabulated in Table 1 using the least-square fitting algorithm (Figure 2(c)).
However, the presence of SY in the formed CB7/luteolin or CB7/EGCG complex enabled the replacement of luteolin or EGCG in the CB7 by SY because CB7/SY complex possessed a higher binding constant
than CB7/luteolin or CB7/EGCG complex, leading to a "switch-off" fluorescence emission response.
The binding constant
([K.sub.b]) and number of binding sites (n) can be determined from emission spectra with (3).
K is the binding constant
of Tm(III)-ASA complex with DNA and [c.sub.DNA] is the concentration of DNA.
In static quenching, various equations expressing the relationship between fluorescence intensity and quencher concentration have been described for the evaluation of the binding constant
and the number of binding sites.
The binding constant
of complex formation was computed from the change in the intensity to the absorption peak at 280nm, according to Benesi-Hildebrand relation,
Sw and Sm are substrates in aqueous and micellar pseudo phase respectable; K'w and K'm are the related first order rate constants and Ks is the binding constant
(Domingos et al., 2003).
Table 1 Binding constant
and thermodynamic parameters for the interaction of 6-shogaol with HSA, obtained from fluorescence quench titration experiments at different temperatures, pH 7.4.