title: Acid-Activatable Michael-Type Fluorescent Probes for Thiols and for Labeling Lysosomes in Live Cells.
abstract: A Michael addition is usually taken as a base-catalyzed reaction. Most fluorescent probes have been designed to detect thiols in slightly alkaline solutions (pH 7-9). The sensing reactions of almost all Michael-type fluorescent probes for thiols are faster in a high pH solution than in a low pH solution. In this work, we synthesized a series of 7-substituted 2-(quinolin-2-ylmethylene)malonic acids (QMAs, substituents: NEt2, OH, H, Cl, or NO2) and their ethyl esters (QMEs) as Michael-type fluorescent probes for thiols. The sensing reactions of QMAs and QMEs occur in distinct pH ranges, pH < 7 for QMAs and pH > 7 for QMEs. On the basis of experimental and theoretic studies, we have clarified the distinct pH effects on the sensing reactivity between QMAs and QMEs and demonstrated that two QMAs (NEt2, OH) are highly sensitive and selective fluorescent probes for thiols in acidic solutions (pH < 7) and promising dyes that can label lysosomes in live cells.
authors.affiliation: Department of Chemistry, University of Science and Technology of China , Hefei 230026, P. R. China.
authors.forename: Chun-Guang
authors.initials: CG
authors.lastname: Dai
authors.affiliation: School of Life Sciences, University of Science and Technology of China , Hefei 230027, P. R. China.
authors.forename: Xiao-Jiao
authors.initials: XJ
authors.lastname: Du
authors.affiliation: Department of Chemistry, University of Science and Technology of China , Hefei 230026, P. R. China.
authors.forename: Qin-Hua
authors.initials: QH
authors.lastname: Song
mesh_terms: D000143:Acids / Q000737:chemistry*; D004348:Drug Labeling; D005456:Fluorescent Dyes / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008247:Lysosomes / Q000737:chemistry*; D008314:Malonates / Q000737:chemistry*; D011804:Quinolines / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000737:chemistry*
chemical_list: D000143:Acids; D005456:Fluorescent Dyes; D008314:Malonates; D011804:Quinolines; D012996:Solutions; D013438:Sulfhydryl Compounds; C030290:malonic acid