Indicator displacement assay

Indicator displacement assays (IDAs) - or, in the specific case of fluorescent indicators, F-IDAs - are based on the next alternative concept described here. A receptor with an affinity for a given analyte is loaded with an indicator, usually a fluorescent or colored dye, whose spectral properties undergo a change upon complexation with the receptor. Treatment of this indicator-receptor complex with the analyte results in the displacement of the indicator from the receptor and a restoration of the indicator s original spectral properties, indirectly reporting analyte coordination (Fig. 27). For effective detection, two main requirements have to be fulfilled (1) the receptor/indicator interaction must be reversible and weaker than the interaction of the receptor with the designated analyte and (2) the indicator must show significantly different optical properties when bound to the receptor and when freely dissolved in solution. 

Horie S, Kubo Y (2009) Fluorescence-based indicator displacement assay for phospho-sugar detection using zinc(II) dipicolylamine-appended phenylboronic acid. Chem Lett 38 616-617... 

Buryak, A. Pozdnoukhov, A. Severin, K. Pattern-based sensing of nucleotides in aqueous solution with a multicomponent indicator displacement assay. Chem. Commun. 2007, 2366-2368. 

The binding of citrate by 4.28 has been investigated by the indicator displacement assay (IDA) method (cf. EDTA titrations, Section 3.1.3). Binding of an organic dye indicator with comparable structure to citrate competes with the substrate for the same binding site. The binding of the indicator... 

Scheme 11.7 Fluorescent indicator displacement assay for acetylcholine developed by Inouye in 1994.31...

Supramolecular sensors comprise binding, transduction and actuator components either in a single molecule or as part of an indicator displacement assay. 

Very recently Anslyn and Zhu reported the method of facile quantification of enantiomeric excess and concentration using an indicator-displacement assay exemplified by analysis of 2-hydroxyacids [88]. 

Piatek AM et al (2004) Threshold detection using indicator-displacement assays An application in the analysis of malate in Pinot Noir grapes. J Am Chem Soc 126 6072-6077... 

Cinchona diimides have also been used to develop a simple colorimetric indicator displacement assay for the determination and chiral discrimination of tartaric acid. Thus, conjugation of 72 with bromophenol blue 73 resulted in the formation of a dark blue complex (A,m lx at 597 nm) that after treatment by an appropriate acid released the protonated form of the indicator with a well-separated absorption maximum at 426 nm. This assay allowed to determine (R,R)-tartaric acid with the detection limit as low as 0.02 mg/ml and efficiently discriminated the enantiomers of tartaric adds,... 

Figure 13.21 Indicator displacement assay for tartrate sensing (upper panel). Displacement isotherms at 597 nm for the addition of (R,R)- and (S,S)-tartaric acid 74 to the complex of 72 and bromophenol blue (73) (c72 and 73=1 x 10 4mol/dm3)...

Among the first modern indicator displacement assays in supramolecular chemistry was the fluorescence-based detection of the neurotransmitter acetylcholine developed by Inouye, Scheme 11.7.31 The fluorescence of the pyrene derivative is quenched by binding to a deprotonated... 

Figure 4. An indicator-displacement assay for colorimetric sensing of SO2 gas (25).

Indicator Displacement Assays with an Organometallic Complex. ... 

Scheme 5 Basic concept of an indicator displacement assay (IDA) the optical properties of an indicator (color, fluorescence) change upon replacement hy an analyte...

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