Determination of Binding Constants by Flow Injection Gradient Technique

Abstract

A new method is based on the flow injection gradient equipped with an acousto-optic tunable filter (AOTF) detector has been developed for the determination of binding constants of substrates with cyclodextrins or micelles. The concentration gradient produced by this method eliminates the need to prepare series of mixtures in which the concentrations of one of the reactants are varied. The fast scanning ability of the AOTF enables the detector to record the whole absorption spectrum of the mixture as it flows through the flow cell. Binding constants can be rapidly determined. The effectiveness of the method was evaluated by determining binding constants of inclusion complex formation between β-cyclodextrin (β-CD) and phenolphthalein and of the incorporation of organic molecules (e.g., p-toluenesulfonic acid (PTS) and benzophenone (BP)) into micelles (CTAB) under steady state condition (no flow) and compared with values determined under the flow injection gradient. The method is particularly effective for charged substrates, e.g., the binding constants obtained between PTS and CTAB and between phenolphthalein and β-CD. Neutral substrate, BP, gives relatively poor accuracy and reproducibility, and these may be due to the adsorption of the substrate onto the flow device.

Cyclodextrin–hydrophobe complexation in associative polymers

“…In eqn (22) and eqn (23), DH and DS are assumed to remain constant within a narrow range of temperatures.…”

“…21 A few attempts have also been made to extend the above techniques to study the complexation thermodynamics of surfactants and polymers with CD. 19,[22][23][24][25][26][27][28][29][30] Tutaj et al 23 used a spectroscopic displacement method, in which phenolphthalein was used as a competitive chromophore, to determine the binding constant of b-cyclodextrin with surfactants. The method is based on decolorization of solution containing phenolphthalein dye in the presence of b-CD.…”

Droplet-Based Microfluidic Flow Injection System with Large-Scale Concentration Gradient by a Single Nanoliter-Scale Injection for Enzyme Inhibition Assay

“…In this work, we developed a microfluidic chip-based system for rapidly generating a droplet array with large-scale concentration gradient by coupling flow injection gradient (FIG) technique with droplet microfluidics (Figure D). FIG technique is a well-established approach in flow injection analysis (FIA), which was built on the basis of the control of the axial dispersion of injected sample zone in a flowing carrier stream and the acquisition of the concentration gradient information from the whole dispersed sample peak. − It has advantages of simple operation, high speed, wide concentration gradient, and good compatibility with biological assays and has been successfully applied in automated preparation of sample or reagent solutions with different concentrations, accurate determination of reaction constants, , and study of drug–protein interactions . In this work, the FIG technique was coupled with droplet-based microfluidics for the first time to generate large-scale concentration gradient in nanoliter-scale droplets with nanoliter sample consumption.…”

Controlled band dispersion for quantitative binding determination and analysis with electrospray ionization‐mass spectrometry

“…Today, lab‐on‐valves (LOV) are in common use (Nishihama et al, 2008) along with autoinjection modules and micro‐channel adaptors (Tanaka et al, 2004). Components used in a diverse set of flow and injection techniques appear during numerous titration analyses (Blaedel & Lasseig, 1965; Dong & Dasgupta, 2003), including those for binding‐constant determinations (Ruzicka, Stewart, & Zagatto, 1976; Tran, Baptista, & Tomooka, 1998).…”