Converting a Solvatochromic Fluorophore into a Protein‐Based pH Indicator for Extreme Acidity

Abstract

Live-cell pH measurements: An environment-sensitive fluorophore (green) was site-specifically introduced on HdeA, an acid-resistant chaperone showing pH-mediated conformational changes under low pH conditions. A survey of the attachment sites led to the discovery of one position on HdeA at which the attached fluorophore showed a strong fluorescence increase upon acidification.

An indole-carbazole-based ratiometric emission pH fluorescent probe for imaging extreme acidity

“…Meanwhile, they showed small Stokes shift and blue fluorescence emission where cells are subject to strong autofluorescence interference. Another promising finding has been reported by Chen's group [28], namely that a protein-based pH probe HdeA58-DMN was Page 6 of 30 A c c e p t e d M a n u s c r i p t 8 converted a solvato chromicfluorophore 4-DMN onto HdeA in E. coli, and expanded for monitoring the extremely acidic pH changes in E. coli bacteria. But the probe still showed single-emission intensity changes by H + .…”

“…Next, we use confocal laser scanning microscope to directly visualize the fluorescence change of E. coli cells harboring CzBI in its periplasmic space. Because of the highly permeable outer membrane of E. coli cells, its periplasmic pH is equilibrated with the extracellular pH[28].To imaging this periplasmic pH under extremely acidic environment, the extracellular pH values are adjusted under a wide range of pH values (pH 7.4, 4.0, 3.0, 2.0 and 1.0)…”

One-pot synthesis of a new rhodamine-based dually-responsive pH sensor and its application to bioimaging

“…37% aqueous solution), NaOH, Na 2 CO 3 , K 2 CO 3 , triethylamine, the solvents, and the metal cation sources, NaCl, KCl, CaCl 2 a 300 MHz Varian Unity Inova spectrometer (Varian Co., USA). Elemental analysis was tested on a Carlo-Erba EA1110 CHNO-S (CarloErba Co., Italy).…”

“…1 Although the extreme acidity (pH<4) is fatal for the majority of living species, microorganisms including 'acidophiles', Helicobacter pylori, and enteric pathogens have evolved to live under such harsh conditions and may cause life-threatening diseases. 2 Hence, measuring of the biological pH under highly acidic conditions is of great importance. Because of their high sensitivity, rapid response, operational simplicity, low cost, in situ and real time monitoring, and noninvasiveness, fluorescent sensors have attracted great attention in environmental and biological pH detection.…”

“On–off–on” Switchable Sensor: A Fluorescent Spiropyran Responds to Extreme pH Conditions and Its Bioimaging Applications

“…14 Some excellent extreme pH sensors have been reported in the literature. 12 −16 It has been found that the introduction of a bulky substituent to the responsive group in these extreme pH sensors is desirable. This finding inspires us to design new extreme pH sensors by introducing different bulky substituents.…”