Chiral-aminoquinoline-based fluorescent pH probe with large stokes shift for bioimaging

Area of Science:

• Organic Chemistry
• Analytical Chemistry
• Biochemistry

Background:

• Aminoquinoline derivatives offer potential for developing novel chemical probes.
• Sensing and monitoring pH changes are crucial in various scientific disciplines.
• Fluorescent probes provide sensitive and real-time detection capabilities.

Purpose of the Study:

• To synthesize novel aminoquinoline derivatives, (R)- and (S)-2-phenyl-2-(quinolin-6-ylamino)ethan-1-ol (R-PEO and S-PEO).
• To evaluate the fluorescent properties and pH-sensing capabilities of the synthesized compounds.
• To explore the application of R-PEO as a fluorescent probe for real-time pH determination and biological imaging.

Main Methods:

• Tandem one-pot three-step CN coupling method with Smiles rearrangement for synthesis.
• Spectroscopic analysis (fluorescence spectroscopy, 1H NMR) to characterize compounds and their properties.
• In vivo biological imaging in S. cerevisiae to assess pH monitoring in living cells.

Main Results:

• R-PEO exhibited significant fluorescence enhancement (turn-on ratio >98-fold) and real-time pH determination in acidic solutions.
• R-PEO demonstrated strong pH-dependent fluorescence with a large Stokes shift (115nm) and linear response in the pH range of 3.8-6.0.
• Protonation of the quinoline unit was confirmed by 1H NMR, and R-PEO's conjugated acid showed planar intramolecular charge transfer (PICT) character.

Conclusions:

• The synthesized aminoquinoline derivative R-PEO is an effective fluorescent probe for sensitive and real-time pH monitoring.
• R-PEO's properties enable accurate detection of minor pH changes within a specific range.
• R-PEO holds promise for in vivo biological imaging applications, specifically for monitoring pH in S. cerevisiae.