Binding rate

Once kon is known, k+l can be estimated in at least three different ways. First, an independent estimate of k, can be obtained from dissociation studies as described above, where, from Eq. (5.15), k+l = (kon — k, )/ E. Second, koa can be measured at several different concentrations of L and a plot of kon against [L] constructed in which, according to Eq. (5.15), k+l is given directly by the slope. This plot will also provide an estimate of k, (intercept). Third, it is possible to perform a simultaneous nonlinear least-squares lit of a family of onset curves (obtained by using different concentrations of L), the fitting routine providing estimates of k+l, k, and /imax (Problem 5.2 provides an opportunity to calculate binding rate constants). 

Cramer and co-workers (1967) have recently measured rate constants as well as equilibrium constants for the association of p-nitrophenol and a series of azo dyes with cydohexaamylose. The general structure of the dyes employed in this study is illustrated in Fig. 4. p-Nitrophenol and p-nitro-phenolate bind to cydohexaamylose with rate constants of about 108 M l sec-1, near the diffusion-controlled limit. Within the series of dyes, however, binding rates decrease by more than seven orders of magnitude as the steric bulk of the dye is increased. Equilibrium constants, on the other hand, are roughly independent of the steric nature of the substrate, indicating that association and dissociation rates are affected by similar... 

The reaction of cyclohexaamylose with a series of p-carboxyphenyl esters is an example of a decelerating effect which may be clearly attributed to nonproductive binding. Rate effects imposed by cyclohexaamylose on the hydrolyses of three such esters are summarized in Table IX. As the hydrophobicity of the ester function is increased by alkyl substitution, the hydrolysis is inhibited the stability of the inclusion complex, on the other... 

N. L. Thompson, Surface binding rates of nonfluorescent molecules may be obtained by total internal reflection with fluorescence correlation spectroscopy, Biophys. J. 38, 327-329 (1982). 

Direct detection of Staphylococcal enterotoxins B (SEB) is illustrated in Fig. 14 which shows binding of SEB to the wavelength-modulated SPR sensor surface coated with respective antibodies for five different SEB concentrations". Figure 15 shows the sensor response to binding after 30-minute SEB incubation and initial binding rate as a function of SEB... 

This study does not support Ekins ambient analyte model in that under flow conditions the rate of analyte capture is not increased as the spot size is decreased. However, as the authors point out, this study is not necessarily a contradiction because Ekins assumptions are based upon achieving equilibrium under static conditions in which diffusion is more likely an important limiting factor in influencing the binding rate. On a more operational note, Sapsford et al. also observed the problem in collecting sufficient signal from a very small spot relative to background noise. 

Fitting the swelling curves of Fig. 7a to the form Q(t) — kt yields values of a greater than or equal to 0.8. Thus the swelling must be considered anomalous, or non-Fickian. In the absence of ionic interactions, this would not be expected since BMA/DMA 70/30 is initially not far below its Tg at 25 °C. Indeed, swelling measurements of this copolymer in hexane show kinetics that are nearly Fickian (a 0.55), as shown in Fig. 7b. Therefore, the anomalous swelling observed in Fig. 7a must be attributed to ion transport and binding rates in the gel. We will return to this point later. 

The development of more efficient ferrous chelates that can increase the binding rate and equilibrium constant with NO, and also the reaction rate of ferrous nitrosyl chelates with sulfite/bisulfite ion, would allow the employment of smaller absorbers, reducing tanks, and L/G (flow rate ratio of scrubbing liquors to flue gas) to achieve the same scrubbing efficiencies. The determination of optimum scrubbing conditions and chemistry such that the formation of undesirable products can be depressed or eliminated would allow the reduction of cost in the area of scrubbing liquor regeneration. This paper addresses the kinetics and thermodynamics of important reactions in-... 

Figure 6. CO binding kinetics for Fe(TPP) as a function of nitrogenous base concentration, [B] ( ) represent ko6g x [I + K2 [B] + K2K2[B]2]/[CO] (left ordinate) for B = Im, [CO] = 5 x lO 4M, [Fe(TPP)] = 6 x 20 M (O) represent ko6g/[CO] (right ordinate) for B = Im-, [DC = 18-C-6] = 0.2M, [CO] = 7.5 x 10 M, [Fe(TPP)] = 6 x 10 M. The CO binding rate constants obtained from this data are listed in Table I. The data for B = Im and derived constants differ somewhat from those in Ref 26 see footnote b, Table I.

Proximal Electronic Control of Heme Reactivity ( ). The deprotonation of a coordinated imidazole results in a large reduction in CO binding rate constants k5(Im)/fc5(Im ) = 170 (Table I). However, the changes are inverse to expectation deprotonation causes the rate constant to decrease, whereas if increased electron donation by the fifth ligand was the critical factor, the rate constant should increase. It is probable that Im- as an axial ligand stabilizes the pentacoordinated ferroporphyrin and that this effect far overbalances any influence of increased charge donation by Im in the transition state on the reaction path by which the hexacoordinated Fe(P)(Im )(CO) is formed. 

We have examined the effects of electron donors on the CO binding rate for a pentacoordinated ferrous porphyrin (27). Comparison of the rates measured in toluene with those in a nonaromatic solvent indicate the maximal effect obtainable from D/A interactions with the phenyl ring of phenylalanine. We have also looked for effects from the addition of N N N -t j pjig l()Jyg gg lenediamine (TMPD), a... 

No effect of TMPD on CO binding rates was detected by either procedure. The plot of binding rates vs. [Py] according to Equation 2 is unchanged by the presence of 1M TMPD. Taking an Fe(TPP)(Py)(CO) solution at either low (0.02M) or high (0.25M) pyridine concentration and titrating with TMPD up to about 1M also... 

Peripheral D/A Control of Heme Reactivity ( ). The equality of CO binding rates in methylene chloride and toluene argues strongly... 

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