Showing papers by "Yunxiang Lu published in 2013"

A new turn-on fluorescent chemosensor based on diketopyrrolopyrrole (DPP) for imaging Zn2+ in living cells.

Abstract: A new turn-on fluorescent chemosensor, DPPL1, was rationally designed and synthesized based on diketopyrrolopyrrole (DPP), which presented high sensitivity and selectivity for Zn2+. Specifically, DPPL1 presented a large emission enhancement and a 70 nm blue-shift upon Zn2+ binding. 1H NMR titrations, studies into the pH effects and DFT calculations further proved that this phenomenon was due to both photo-induced electron transfer (PET) and intra-molecular charge transfer (ICT) processes. More importantly, DPPL1 was successfully used for imaging Zn2+ in living HeLa cells. To the best of our knowledge, this is the first DPP-based fluorescent chemosensor to recognize Zn2+ ions in living cells with a large blue-shift and a fluorescent enhancement based on both photo-induced electron-transfer (PET) and intramolecular charge-transfer (ICT) effects. Meanwhile, we have also provided a new effective platform for the development of fluorescent chemosensors for other analytes.

The Stabilization Effect of Dielectric Constant and Acidic Amino Acids on Arginine–Arginine (Arg–Arg) Pairings: Database Survey and Computational Studies

Abstract: Database survey in this study revealed that about one-third of the protein structures deposited in the Protein Data Bank (PDB) contain arginine–arginine (Arg–Arg) pairing with a carbon···carbon (CZ···CZ) interaction distance less than 5 A. All the Arg–Arg pairings were found to bury in a polar environment composed of acidic residues, water molecules, and strong polarizable or negatively charged moieties from binding site or bound ligand. Most of the Arg–Arg pairings are solvent exposed and 68.3% Arg–Arg pairings are stabilized by acidic residues, forming Arg–Arg–Asp/Glu clusters. Density functional theory (DFT) was then employed to study the effect of environment on the pairing structures. It was revealed that Arg–Arg pairings become thermodynamically stable (about −1 kcal/mol) as the dielectric constant increases to 46.8 (DMSO), in good agreement with the results of the PDB survey. DFT calculations also demonstrated that perpendicular Arg–Arg pairing structures are favorable in low dielectric constant en...

Noncovalent interactions in halogenated ionic liquids: theoretical study and crystallographic implications.

Abstract: In recent years, several specific imidazolium-based ionic liquids with halogen substituents on the imidazole ring as well as on the alkyl chains have been reported. In this work, noncovalent interactions in four halogenated ionic liquids, i.e. 2-bromo-/iodo- and 4,5-dibromo-/diiodo-1,3-dimethylimidazolium trifluoromethanesulfonates, were systematically investigated using density functional theory calculations. The structural and energetic properties of the ion pairs for such ionic liquids have been fully examined and compared with the non-halogenated ones. It was found that C–X⋯O halogen bonds, C–H⋯O hydrogen bonds, and electrostatic interactions with the anion located over the imidazole ring in the ion pairs. In addition, the structures and energetics of two ion pairs for such ionic liquids were also explored to reproduce experimental observations. The halogen-bonded ring structures and the conformers with the concurrent C–H⋯O and C–X⋯O contacts were predicted, consistent with the X-ray crystal structures of corresponding organic salts. Finally, the implications of the observed structural and energetic features of ion pairs on the design of halogen-bonding ionic liquids were discussed. The results presented herein should provide useful information in the development of novel halogenated ionic liquids used for specific tasks ranging from organic synthesis to gas absorption.

Density functional theory study on the interaction between metalloporphyrins and NH3

Abstract: The binding behaviors of eight bivalent metalloporphyrins (MPs) (MZn, Mg, Cu, Mn, Fe, Co, Ni, and Cd) with NH3 were investigated by density functional theory. For both MPs and corresponding complexes MPs-NH3, good linear correlations are found between the partial charge on metal M and that on atom N (nitrogen of porphyrin) as well as the MN bond length. Natural population and frontier orbital analysis demonstrate that charge transfer in CoP-NH3 is much easier and greater. As a consequence of the charge transfer and the hybridization of molecular energy levels, striking disparities of electronic properties of MPs-NH3 are observed. Particularly, a modest linear relationship is obtained between the magnitude of charge transfer and the binding energy. The much greater Fukui functions of CoP, together with its larger binding strength, suggest that CoP is more favorable to the interaction with NH3, which might be a promising sensing material to response NH3. © 2013 Wiley Periodicals, Inc.