Zhen Shi

Three Rhodamine-Based “Off–On” Chemosensors with High Selectivity and Sensitivity for Fe3+ Imaging in Living Cells

Three new rhodamine-based probes Y1-Y3 were synthesized as off-on chemosensors for Fe(3+) imaging in living cells. The recognizing behaviors were investigated both experimentally and computationally. The crystal structure of the complex Y3-Fe(3+) revealed that Fe(3+) preferred to coordinate with the N atom of benzothiazole moiety rather than the O atom of carboxyl group.

Synthesis of chlorinated fluoresceins for labeling proteins

Two novel chlorinated fluoresceins 4,7,2,7-tetrachloro-6-(5-carboxypentyl)fluorescein (8a) and 4,7,4,5-tetra-chloro-6-(5-carboxypentyl)fluorescein (8b) were synthesized as fluorescent probes for labeling proteins. These two fluoresceins contain 6-aminohexanoic acid as spacer linker to minimize the fluorescence quenching of the fluorescein molecules by the proteins to be labeled.

Visualizing tributyltin (TBT) in bacterial aggregates by specific rhodamine-based fluorescent probes

Here we present the first examples of fluorescent and colorimetric probes for microscopic TBT imaging. The fluorescent probes are highly selective and sensitive to TBT and have successfully been applied for imaging of TBT in bacterial Rhodobacter ferrooxidans sp. strain SW2 cell-EPS-mineral aggregates and in cell suspensions of the marine cyanobacterium Synechococcus PCC 7002 by using confocal laser scanning microscopy.

Novel conjugation of norvancomycin-fluorescein for photodynamic inactivation of Bacillus subtilis.

A simple and unique conjugation of norvancomycin-fluorescein (VanF) has been achieved. It was characterized by UV-vis and fluorescence spectra and confirmed by MALDI-TOF mass spectrum. The photodynamic assay indicated that VanF effectively inactivated the Gram-positive Bacillus subtilis (ATCC 6633) from clinic with inactivation rate of 30-70% within 1-7.5 μM. In vitro, VanF showed low antimicrobial activity with value of >128 μg/mL, binding affinity with value of 180 nM per 10(8) cells/mL against the bacteria strains. The fluorescence imaging showed that VanF could label the B. subtilis strain, but not the Escherichia coli (ATCC 25922), Enterococcus faecalis (ATCC 51299, VanD), and VRE strains from clinic.

Synthesis and biological applications of two novel fluorescent proteins-labeling probes

Two novel chlorinated fluoresceins 2,4,5,7-tetrachloro-6-(5-carboxypentyl)-4,7-dichloro fluorescein succinimidyl ester (1G) and 2,4,5,7-tetrachloro-6-(3-carboxypropyl)-4,7-dichlorofluorescein succinimidyl ester (2G) were synthesized as fluorescent probes for labeling proteins. Structures of target compounds and intermediates were determined via IR, MS, (1)H NMR and element analysis. The investigation in immunofluorescence histochemistry showed them had strong fluorescence, high photostability and good biocompatibility.

Synthesis of New BAPTA Calcium Chelators

Abstract A series of new 1,2-bis-(2-aminophenoxyethane) N,N,N′,N′-tetraacetic acid (BAPTA) chelators were designed and synthesized to form novel and improved fluorescent indicators. Substituted 2-nitrophenol, acting as the material, reacted in five steps to give BAPTA-derived chelators. The Ca2+ affinity of BAPTA chelators could increase significantly by addition of electron-donating groups and decrease by electron-withdrawing groups. Compounds 3a–e were treated with iron powder instead of hydrogenation, obtaining a satisfying yield. The structures of all compounds were characterized by infrared, 1H NMR, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) spectra.

Study on the inclusion behaviour and solid inclusion complex of lomustine with cyclodextrins

The water soluble solid inclusion complex of three native or modified cyclodextrins (CDs) including β-cyclodextrin (β-CD), hydroxypropyl-β-cyclodextrin (Hp-β-CD) and 2,6-di-o-methyl-β-cyclodextrin (DIME-β-CD) and Lomustine (CCNU) were presented with the orthogonal experiment investigation of the reaction conditions. The inclusion behaviors were comparatively investigated by nuclear magnetic resonance in combination with infrared spectroscopy, thermogravimetric analysis, X-ray diffractometry and scanning electron microphotographs. The experimental results jointly demonstrated that the entrance of CCNU into the cavity of the CDs by intermolecular forces as well as hydrophobic forces and resulting in the significantly improvement of the thermostability of CCNU.Graphical Abstract

Synthesis and characterization of bis[2-(1H-benzimidazol-2-yl)benzoato]nickel(II), and its use for preparation of dimethyl carbonate from methanol and CO2

A new complex, bis[2-(1H-benzimidazol-2-yl)benzoato]nickel(II) (NiL2), has been synthesized and characterized. It was used as catalyst for synthesis of dimethyl carbonate (DMC) from methanol and CO2 in the presence of dicyclohexyl carbodiimide (DCC) as promoter. The effects of temperature, reaction time, and amount of catalyst on the reaction, and the reusability of the catalyst, were investigated. A catalytic mechanism is proposed. The results revealed that NiL2xa0+xa0DCC had excellent catalytic activity, because this catalytic system promoted facile formation of DMC, with acceptable yield, in the presence of a small amount of NiL2 and under moderate conditions (80xa0°C, 1.0xa0MPa). Moreover, the catalyst has been consecutively used five times without significant loss of activity.