Guidelines in Implementing Enantioselective Indicator-Displacement Assays for α-Hydroxycarboxylates and Diols

Pattern-Based Discrimination of Enantiomeric and Structurally Similar Amino Acids: An Optical Mimic of the Mammalian Taste Response

This manuscript describes an optical enantioselective pattern-based sensing array. A differential array of enantioselective indicator displacement assays was constructed and used to demonstrate simultaneous discrimination of enantiomeric and structurally similar alpha-amino acids. Interpretation of the output patterns by principle component analysis leads to the separation of enantio- and chemoselective information along orthogonal variance axes when chiral receptors of opposite enantiomeric preference are included. A general principle is delineated that correlates array design with the achievement of enantiomeric discrimination analogous to the mammalian gustation response to the amino acids.

Water-soluble fluorescent boronic acid compounds for saccharide sensing: substituent effects on their fluorescence properties

Four new naphthalene-based boronic acid compounds (1-4) were synthesized. The effect of various carbohydrates on their fluorescence properties has been studied in aqueous phosphate buffer at pH 7.4. Different substitutions on the aniline group of the naphthalene ring resulted in significant differences in fluorescence properties for these four compounds. Compound 1 shows ratiometric fluorescence changes upon addition of a sugar. Compounds 2 and 3 do not show ratiometric fluorescence changes but show very large fluorescence intensity changes (about 70-fold fluorescence intensity increase). In addition to the quantifiable fluorescence property changes upon sugar addition, the fluorescence color changes of 1-3 are also visible to the naked eye. However, amidation of the aniline nitrogen atom significantly diminishes the fluorescence intensity of compound 4. The crystal structure of one boronic acid provided some insight into the structural features that are important for the fluorescence properties of these compounds.

A Colorimetric Boronic Acid Based Sensing Ensemble for Carboxy and Phospho Sugars

[structure: see text] A cadmium-centered tris-boronic acid receptor was synthesized, and its binding properties toward various anionic sugars were determined. This receptor shows high affinity for different anionic sugars, especially gluconic acid, which has an association constant near approximately 10(7) M(-)(1) at neutral pH. Further, using an indicator displacement assay, a color change of pyrocatechol violet was observed upon addition of anionic sugars. This colorimetric test was used as a facile screening technique to qualitatively analyze guest affinities.

A naked-eye sensing ensemble for the selective detection of citrate—but not tartrate or malate—in water based on a tris-cationic receptor

Citrate 3 can be selectively detected in aqueous solvents even in the presence of malate or tartrate using a naked-eye detection system based on the complex between tris-cation 1 and carboxyfluorescein 2.

Colorimetric Enantiodiscrimination of α-Amino Acids in Protic Media

A new method is described for the determination of optical purity of alpha-amino acid samples in protic media. No derivatization of the analyte or multistep synthesis is required, and high accuracy is obtained from the colorimetric output. Chiral discrimination is achieved through the use of an optically pure trans-1,2-diaminocyclohexane-derived Cu(II)-containing host that differentiates amino acid enantiomers by a factor of about 2. Enantioselective signaling arises from the implementation of an indicator displacement assay based on competitive Cu(II) coordination involving the chiral Cu(II)-containing host, the amino acid guest, and a metal ion indicator. The molecular structure of the host/guest complex was determined by X-ray analysis and exhibits chelation of the Cu(II) center by the amino acid to provide substrate organization.