Indicator-displacement

The H—NMR spectra indicate displacements of chemical shifts for the double bond protons of MA and TBSM and protons of the CH2—Sn group which suggest that two complex types are present in the mixture of the monomer pairs under study ... 

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. 

Hanshaw RG, Hilkert SM, Hua J et al (2004) An indicator displacement system for fluorescent detection of phosphate oxyanions under physiological conditions. Tetrahedron Lett 45 8721-8724... 

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]. 

Studies have also been carried out in systems containing excess BF3 (17,18). The results (18) show that when the base is dimethyl ether, anisole, tetrahydrofuran, or pyridine, the exchange of BF3 is rapid and probably proceeds through an electrophilic displacement reaction in which the excess BF3 attacks the complex. These reactions all have activation energies of less than 10 kcal/mole, eliminating the possibility of a dissociation process. The data available, however, do not allow a complete evaluation of the reaction mechanism. Studies carried out on BF3-methanol complexes by 19F NMR (17) indicate displacement reactions having an activation energy of 5.3 kcal/mole. 

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... 

The exact shape of the reconstructed surface (in effect, the nature of the missing stresses ). The information provided by the analysis of the surface excitonic structure seems to indicate displacements only among equivalent molecules. 

Fig. 8-3 Probable mechanism of bond cleavage by lysozyme. The thick solid line structure is the substrate, and the lightface groups are on the enzyme. The small arrows indicate displacement of electron pairs during the reaction.

CalcLilaicd energy as a function of the outward displacement w of a (111) surface atom in silicon when the dangling hybrid is doubly occupied or empty. The constitution of the dangling hybrid is indicated at the bottom of the figure. Arrows indicate displacements predicted by Chadi (1978). 

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)...

Fig. 17. Structure of Ca, CrN, projected on (001). N atoms center the Ca,Cr oetahedra. The larger circles represent Ca atoms, while the smaller circles represent Cr atoms. Shading indicates displacement by c/2...

Fig. 19. Projection of the Ba(N structure on (010). Ba atoms center the tncapped trigonal prisms. Shatlitui indicates displacement by b, 2. Condensing the a/ide groups to a single site yields the Pbl C i structure...

Fig. 23. Structure of UNCI with the PbFCI structure projected on (100). U atoms center tricapped trigonal prisms. Large circles represent Cl atoms. Small circles represent N atoms. Light and dark shading indicates displacement by a, 2...

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