Qiwen He

Publications of Qiwen He

• A Turn-On Fluorescent Sensor for Detecting Nickel in Living Cells.

  Authors: Sheel C Dodani, Qiwen He, Christopher J Chang

  Journal of the American Chemical Society. 12/2009;

  We present the synthesis and properties of Nickelsensor-1 (NS1), a new water-soluble, turn-on fluorescent sensor that is capable of selectively responding to Ni(2+) in aqueous solution and in livingWe present the synthesis and properties of Nickelsensor-1 (NS1), a new water-soluble, turn-on fluorescent sensor that is capable of selectively responding to Ni(2+) in aqueous solution and in living cells. NS1 combines a BODIPY chromophore and a mixed N/O/S receptor to provide good selectivity for Ni(2+) over a range of biologically abundant metal ions in aqueous solution. In addition to these characteristics, confocal microscopy experiments further show that NS1 can be delivered into living cells and report changes in intracellular Ni(2+) levels in a respiratory cell model.

• Experimental and Theoretical Study of Tunable 1,3-Lithium Shift of Propargylic/Allenylic Species, Transmetallation, and Pd-Catalyzed Cross-Coupling Reactions.

  Authors: Jinbo Zhao, Yu Liu, Qiwen He, Yuxue Li, Shengming Ma

  Chemistry (Weinheim an der Bergstrasse, Germany). 09/2009;

  The highly selective tuning of the isomerization from 1-arylalka-1,2-dien-1-yllithium to 1-arylalka-1,2-dien-3-yllithium has been realized in the deprotonation of 1-arylalk-1-yne (conditions A and B)The highly selective tuning of the isomerization from 1-arylalka-1,2-dien-1-yllithium to 1-arylalka-1,2-dien-3-yllithium has been realized in the deprotonation of 1-arylalk-1-yne (conditions A and B) and carbolithiation of 1-arylbut-3-en-1-yne with alkyllithium (conditions C and D). Subsequent transmetallation and Pd-catalyzed Negishi coupling reactions afforded 1,1-diaryl or 1,3-diaryl allenes with high selectivity. Deuterium-labeling cross experiments indicated that an intermolecular lithiation process occurred in both 1,3-lithium shift conditions (conditions B and D). 1-Arylalka-1,2-diene was confirmed experimentally to be the intermediate. A computational study at the B3LYP level for the isomerization indicated that the acidity of H at the 3-position is higher than that of the H at the 1-position of 1-phenyl-1,2-butadiene. Under conditions B, iPr(2)NH acts as a proton carrier to finish the 1,3-lithium shift. The overall activation barrier for the rate-determining step in the solvated models is approximately 21.0 kcal mol(-1), indicating that the isomerization is reasonable at room temperature. For the isomerization under conditions D, DFT calculations indicated that the addition of TMEDA (tetramethylethylenediamine) and HMPA (hexamethylphosphoramide) changes the global minimum of the system; among the possible mechanisms (P1-P5) considered, the mechanism catalyzed by dilithiated species (P5) is the most probable one. The overall activation barriers for isomerization in THF and TMEDA solvated models are 22.6 and 19.7 kcal mol(-1), respectively, proving that the isomerization may proceed at RT in THF or at -78 degrees C with TMEDA, due to the fact that the solvation of the additives may increase the concentration of 1-phenyl-1,2-butadienyllithium monomer by a deaggregation effect.

• Preparation and use of Leadfluor-1, a synthetic fluorophore for live-cell lead imaging.

  Authors: Evan W Miller, Qiwen He, Christopher J Chang

  Nature protocols. 02/2008; 3(5):777-83.

  Leadfluor-1 (LF1) is a small-molecule fluorescent sensor for detecting lead in biological and environmental samples, including live cells. This dye uses a xanthenone fluorescent scaffold coupled to aLeadfluor-1 (LF1) is a small-molecule fluorescent sensor for detecting lead in biological and environmental samples, including live cells. This dye uses a xanthenone fluorescent scaffold coupled to a dicarboxylate pseudocrown ether receptor to achieve selective detection of Pb(2+) in the presence of biologically relevant metal ions, including divalent calcium, magnesium and zinc. LF1 fluorescence increases by up to 18-fold on binding Pb(2+). In this protocol, we describe the synthesis and application of LF1 to imaging lead accumulation within live cells. The preparation of LF1 is anticipated to take 14-21 d, and the imaging assays can be performed in 1-2 d with cultured cells.

• A bright and specific fluorescent sensor for mercury in water, cells, and tissue.

  Authors: Sungho Yoon, Evan W Miller, Qiwen He, Patrick H Do, Christopher J Chang

  Angewandte Chemie (International ed. in English). 02/2007; 46(35):6658-61.

• A selective fluorescent sensor for detecting lead in living cells.

  Authors: Qiwen He, Evan W Miller, Audrey P Wong, Christopher J Chang

  Journal of the American Chemical Society. 08/2006; 128(29):9316-7.

  We present the synthesis, properties, and biological applications of Leadfluor-1 (LF1), a new water-soluble, turn-on fluorescent sensor that is capable of selectively imaging Pb2+ in aqueous solutionWe present the synthesis, properties, and biological applications of Leadfluor-1 (LF1), a new water-soluble, turn-on fluorescent sensor that is capable of selectively imaging Pb2+ in aqueous solution and in living cells. LF1 combines a fluorescein chromophore and a pseudocrown receptor to provide good selectivity for Pb2+ over a range of biologically and environmentally relevant metal ions in aqueous solution, with sensitivity to parts per billion EPA limits for allowable lead in drinking water. In addition to these attributes, imaging experiments further show that LF1 is the first small-molecule reagent that can be delivered into living cells and report changes in intracellular Pb2+ levels.

• What can a metal catalyst do with allenes? One-step formation of steroid scaffolds from readily available starting materials.

  Authors: Shengming Ma, Ping Lu, Lianghua Lu, Hairong Hou, Jiemin Wei, Qiwen He, Zhenhua Gu, Xuefeng Jiang, Xing Jin

  Angewandte Chemie (International ed. in English). 09/2005; 44(33):5275-8.

• Pd(0)-catalyzed highly selective synthesis of 1,1-diarylpropadienes and 1,3-diarylpropynes from 1-aryl-1-propynes and aryl halides.

  Authors: Shengming Ma, Qiwen He, Xiuhui Zhang

  The Journal of organic chemistry. 05/2005; 70(8):3336-8.

  Under different reaction conditions, 1,1-diarylpropadienes and 1,3-diarylpropynes can be prepared respectively by the sequential lithiation of 1-aryl-1-propynes, transmetalation, and theUnder different reaction conditions, 1,1-diarylpropadienes and 1,3-diarylpropynes can be prepared respectively by the sequential lithiation of 1-aryl-1-propynes, transmetalation, and the corresponding Pd(0)-catalyzed cross-coupling with aryl halides. A rationale for the formation of 1,3-diarylpropynes is proposed.

• A 1,3-lithium shift of propargylic/allenylic lithium and the subsequent transmetalation coupling reaction with aryl halides.

  Authors: Shengming Ma, Qiwen He

  Angewandte Chemie (International ed. in English). 03/2004; 43(8):988-90.