Chang-Liang Sun

Synthesis of mono-(p-dimethylamino)styryl-containing BOPHY dye for a turn-on pH sensor

Mono-substitutional bis(difluoroboron)1,2-bis((1H-pyrrol-2-yl)methylene)hydrazine (BOPHY) 3a with a (p-dimethylamino)styryl group in the α-position was confirmed to be synthesized by the Knoevenagel-type condensation. Dimethylamino-containing BOPHY dye 3a is almost non-fluorescent by the ICT effect. Upon the protonation of the tertiary amine function of 3a, the strong fluorescence (Φf = 0.98) was released and the fluorescence intensity was dramatically increased by one thousand fold. BOPHY 3a can be used as a pH probe.

A New Water-Soluble Phosphorus-Dipyrromethene and Phosphorus-Azadipyrromethene Dye: PODIPY/aza-PODIPY

PODIPY and aza-PODIPY have been successfully prepared by the treatment of dipyrromethene and azadipyrromethene with POCl3 in the presence of Et3 N. The new PODIPY and aza-PODIPY dyes are found to have photophysical properties. PODIPY and aza-PODIPY are water-soluble, and aza-PODIPY is suited for labeling living Hep-2 cells for imaging assays in the near-infrared region. Molecular orbital calculations show that the increase in the HOMO-LUMO band gap for the lowest energy absorption bands is observed in the new phosphorus-containing aza-PODIPY, and the HOMO and LUMO energies of aza-PODIPY are found to be higher than those of aza-BODIPY.

1,8-Naphthyridine-based molecular clips for off–on fluorescence sensing of Zn2+ in living cells

A new 1,8-naphthyridine-based clip-like receptor as an “off–on” fluorescent probe was designed and synthesised for selectively sensing Zn2+ in aqueous media and living cells.

The effect of water molecules upon the hydrogen-bonding cooperativity of three-stranded antiparallel β-sheet models

The effect of water molecules upon the hydrogen-bonding cooperativity of three-stranded antiparallel β-sheet models has been studied by quantum chemical calculations at the MP2/6-311++G(3df,2p)//MP2/6-31G** level. Our calculation results indicate that the hydrogen-bonding lengths and the atom charge distribution are affected by the H2O molecules, especially for those in the same amide unit directly bonded. The hydrogen-bonding cooperativity significantly increases the binding energy of the LR or SR hydrogen-bonding ring in the three-stranded β-sheet structures and the influence is also gradually increased as more H2O molecules are added. We found that the perturbation energies are also affected as the H2O molecules are added and this supports that the cooperative enhancement is closely related to the orbital interaction. We have also found that the charge transfer among the three diglypeptides is obviously influenced by the H2O molecules.

The nonadditivity of stacking interactions in adenine–thymine and guanine–cytosine stacked structures: Study by MP2 and SCS-MP2 calculations

The nonadditivity of stacking interactions in stacked structures of adenine–thymine and guanine–cytosine base pairs is investigated by MP2 and SCS-MP2 calculations with 6-311++G** and aug-cc-pvdz basis sets. The calculation results indicate that the intermolecular distances in the multi-stacked structures do not become shorter obviously as the stacked structure added. The middle stacking interaction energies in the multi-stacked structures also become weaker than that of dimer structures. It is found that the total stacking interaction energies of the trimer and tetramer stacked structures do not increase proportionally. Based on the results, we suggest that there is negative cooperativity of the stacking interactions in the adenine–thymine and guanine–cytosine stacked structures.