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Fluorescent Probes With High pKa Values Based on Traditional, Near-Infrared Rhodamine, and Hemicyanine Fluorophores for Sensitive Detection of Lysosomal pH Variations

Fluorescent Probes With High pKa Values Based on Traditional, Near-Infrared Rhodamine, and Hemicyanine Fluorophores for Sensitive Detection of Lysosomal pH Variations

Wafa Mazi, Rashmi Adhikari, Yibin Zhang, Shuai Xia, Mingxi Fang, Rudy L Luck, Momoko Tajiri, Ashutosh Tiwari, Marina Tanasova, Haiying Liu

Methods. 2019 Sep 15;168:40-50.

PMID: 31344405

Abstract:

Sterically hindered fluorescent probes (A-C) have been developed by introducing 2-aminophenylboronic acid pinacol ester to a traditional, A, a near-infrared rhodamine dye, B, and a near-infrared hemicyanine dye, C, forming closed spirolactam ring structures. Probe A was non-fluorescent under basic pH conditions whereas probes B and C were moderately fluorescent with fluorescence quantum yields of 9% and 5% in pH 7.4 PBS buffer containing 1% ethanol, respectively. With all probes increasing acidity leads to significant increases in fluorescence at 580 nm, 644 and 744 nm for probes A, B and C with fluorescence quantum yields of 26%, 21% and 10% in pH 4.5 PBS buffer containing 1% ethanol, respectively. Probes A, B and C were calculated to have pKa values of 5.81, 5.45 and 6.97. The difference in fluorescence under basic conditions is ascribed to easier opening of the closed spirolactam ring configurations due to significant steric hindrance between the 2-aminophenylboronic acid pinacol ester residue and an adjacent H atom in the xanthene derivative moiety in probe B or C. The probes show fast, reversible, selective and sensitive fluorescence responses to pH changes, and are capable of sensing lysosomal pH variations in living cells.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP191171558	2-Aminophenylboronic acid pinacol ester		191171-55-8	Price
LS793390	1,5-Dimethyl-1H-pyrazole-4-boronic acid,pinacol ester			Price

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