Small quinolinium-based enzymatic probes via blue-to-red ratiometric fluorescence

Abstract

A small fluorescence ratiometric probe consisting of a single dye species, N-methyl-6-hydroxyquinolinium (MHQ), and coupled enzymatic substrates, exhibits a dramatic colour change (deep blue to red) and possesses a huge response ratio (over 2000 fold) upon specific recognition of target enzymes. Such dramatic responses are attributed to the excited-state proton transfer processes of MHQ molecules in water. Here the detection of β-galactosidase and porcine pancreatic lipase is successfully demonstrated and this class of molecules has the potential to be developed as a "naked-eye" probe in vitro.

Large Stokes Shift Ionic‐Liquid Dye

“…The color of this solvatochromatic dye molecule depends strongly on the polarity of the surrounding, as the permanent dipole moments strongly change upon excitation from the ground to the excited state. Thus [6MQz] has been used as dye for understanding solvation processes and proton transfer to solvents . In some cases the polarity probe was incorporated into biomolecules such as sugars or enzymes for probing the chemical environment and providing biocompatibility .…”

“…Stabilized by solvation effects in water the OH proton is released in the excited state and the fluorescence gives the characteristic response of the non protonated form of the dye [6MQz].This finding underlines that the embedded [6MQc] + in the IL dye can be used as photo acid as reported by other groups. [14][15][16][17][18][19][20] In conclusion, we have presented an ew ionic-liquid dye showing al arge Stokes shift, rather high emission quantum yields,p hotostability,a nd good solubility in diverse solvents. In aprotic solvents and ionic liquids including the same weakly interacting anion the solubility of the ionic-liquid dye can increase up to an order of magnitude compared to the initial molecular dye [6MQz] (see SI8).…”

“…[14][15][16][17][18][19][20][21][22] In some cases the polarity probe was incorporated into biomolecules such as sugars or enzymes for probing the chemical environment and providing biocompatibility. [10,11,18,19] Whereas other dyes have been extensively applied to probe the polarity of ionic liquids,t he protonated form of [6MQz] has never been used as moiety of an ionic liquid itself. [23,24] Thus,t he goal of our work was to incorporate the dye N-methyl-6-oxyquinolone [6MQz] in its protonated form as acation into an ionic liquid (IL) and thus to synthesize an IL dye.T he resulting ionic liquid dye N-methyl-6-hydroxyquinolinium bis(trifluoromethylsulfonyl) imide ]involves anion metathesis reaction and is shown in Scheme 1.…”

“…Thec olor of this solvatochromatic dye molecule depends strongly on the polarity of the surrounding,a st he permanent dipole moments strongly change upon excitation from the ground to the excited state.T hus [6MQz] has been used as dye for understanding solvation processes and proton transfer to solvents. [14][15][16][17][18][19][20][21][22] In some cases the polarity probe was incorporated into biomolecules such as sugars or enzymes for probing the chemical environment and providing biocompatibility. [10,11,18,19] Whereas other dyes have been extensively applied to probe the polarity of ionic liquids,t he protonated form of [6MQz] has never been used as moiety of an ionic liquid itself.…”

A Pyrone‐based Ratiometric Probe for Galactosidase with Dramatic Color and Fluorescence Changes

“…[4][5][6][7][8][9][10][11] However, a few ratiometric fluorescent probes have been developed due to the environmental artifact-free signaling properties. [12][13][14] For example, Zhu group recently published an excellent ratiometric fluorophore for β-Gal from a precursor, benzopyrone. 12 The precursor was deliberately prepared from 2-hydroxyacetophenone over two-step syntheses but the process is a labor-intensive work and the yield is as low as 40%.…”