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Biomedical subjects

Gang Xue

Publications and source records attributed to Gang Xue.

27 records · Page 2Linked to original sources
PubMed2003

Trivalent boron as an acceptor in donor-pi-acceptor-type compounds for single- and two-photon excited fluorescence.

The synthesis, structure, and fluorescence properties of a series of new donor-pi-acceptor (D-pi-A) type compounds, with a trivalent boron, protected by two mesityl groups, as acceptor, and with various typical donors and different pi-conjugated bridges, are reported. All these stable organoboron compounds show intense single-photon excited fluorescence (SPEF) and two-photon excited fluorescence (TPEF) in a wide spectral range from blue to green, with the spectral peak position of the SPEF being basically the same as that of the TPEF. The remarkably strong Cbond;B(mesityl)(2) bonding, and the well-conjugated pi-system, shown in X-ray crystal structures of two compounds, indicate some charge transfer features of the ground state. Meanwhile, spectral data indicate that the charge transfer from donor to acceptor is greatly enhanced in the excited states. Based on typical structural data and comprehensive spectral data, the following structure-property relationships can be drawn: 1) the moderate arylamino donor can more effectively enhance the SPEF and TPEF intensities than can the strong alkylamino donor; 2) stilbene is a better pi-bridge than styrylthiophene for its capability of enhancing and blue-shifting the SPEF and TPEF of the corresponding D-pi-A compounds; and 3) when compared to its boron-free precursors and other analogues, -B(mesityl)(2) invariably and consistently acts as an effective SPEF and TPEF fluorophore in all this series of organoboron compounds, which may result from its strong pi-electron-withdrawing and charge transfer-inducing nature in the ground-state and, more dominantly, in the excited-state. Combining all the above positive structure factors, trans-4'-N,N-diphenylamino-4-dimesitylborylstilbene (compound 3) stands out as the optimized green SPEF and TPEF emitter. This compound exhibits an SPEF quantum yield Phi of 0.91 at 522 nm in THF, a TPEF cross-section sigma' that is an order of magnitude larger than that of its boron-free precursor upon excitation by 800 nm femto-second laser pulses, and a two-photon absorption section sigma of 3.0 x 10(-48) cm(4) s. In the blue light region, trans-4'-N-carbazolyl-4-dimesitylboryl-stilbene (compound 4) shows significant SPEF and TPEF properties, with Phi=0.79 at 464 nm in THF and a large sigma' value, which is five times that of fluorescein upon excitation by 740 nm femto-second laser pulses.

Journal Article↗
PubMed2003

[A kinetic model of chlorine decay reacting with organics in water distribution systems].

A combined first and second-order model was developed to describe the bulk decay of chlorine in water distribution systems. The parameters of model were determined by deriving the best fit with a lot of experimental data. The complex relationships between bulk decay and the temperature, the initial chlorine concentration and TOC were quantificationally described in the model. Except for the initial stages the combined model can be simplified into the first-order model and these relationships can be simplified into a linear increase with TOC, a linear decrease with initial chlorine concentration and an exponential relationship with the temperature. The model also explained why chlorine decays more rapidly in the initial stages. The accuracy of model was verified by using the experimental data. The results showed that the combined model has better agreement with the experimental data than the conventional first-order model.

Chlorine↗
PubMed2003

[Study on the plant community of Fritillaria cirrhosa].

OBJECTIVE: To provide scientific basis for natural cultivation of Fritillaria cirrhosa. METHOD: The cluster analysis to the Bray--Curtis distance coefficient of community plot was carried out to divide the community types of F. cirrhosa. RESULT AND CONCLUSION: The community of F. cirrhosa's natural cultivation can be divided into six types: Sibiraea angustata community, Rhododendron litangense community, Salix sclerophylla community, Dasiphora fruticosa + Spiraea alpina + S. myrtilloides community, Sabina pingii var. wilsonii community, Polygonum viviparum + P. sphaerostachyum community, and the ecological characteristics such as the composition of community and ecological distribution have been showed.

Altitude↗
PubMed2002

N-ethylpyridinium bis(2-thioxo-1,3-dithiole-4,5-dithiolato)nickelate.

The title compound, (C(7)H(10)N)[Ni(C(3)S(5))(2)] or (Etpy)[Ni(dmit)(2)] (where Etpy is the N-ethylpyridinium cation, C(7)H(10)N(+), and dmit is the 2-thioxo-1,3-dithiole-4,5-dithiolate dianion, C(3)S(5)(2-)), crystallizes in the P-1 space group with two molecules in the asymmetric unit. The [Ni(dmit)(2)](-) monoanion has a planar D(2h) conformation, with the central Ni atom and the four coordinated S atoms forming an NiS(4) square plane. The six-membered ring of the Etpy cation also shows good planarity, as expected. There are two main types of disorder in the two Etpy cations. Several short intermolecular interactions are present, such as S...S, Ni...S and Ni...Ni, which help to form the enhanced three-dimensional structure of the crystal.

Journal Article↗
PubMed2002

2'-Hydroxy-4"-dimethylaminochalcone.

The title compound, 3-[4-(dimethylamino)phenyl]-1-(2-hydroxyphenyl)prop-2-en-1-one, C(17)H(17)NO(2), is a chalcone derivative substituted by 2'-hydroxyl and 4"-dimethylamino groups. The crystal structure indicates that the aniline and hydroxyphenyl groups are nearly coplanar, with a dihedral angle of 10.32 (16) degrees between their phenyl rings. The molecular planarity of this substituted chalcone is strongly affected by the 2'-hydroxyl group.

Journal Article↗
PubMed2002

Tetra-n-butylammonium bis(2-thioxo-1,3-dithiole-4,5-dithiolato-kappa2S4,S5)nickelate(III).

The crystal structure of the title compound, (C(16)H(36)N)[Ni(C(3)S(5))(2)], is isomorphous with that of the corresponding Pt complex but different from the structures reported for compounds of the same chemical composition, and so provides a new crystalline phase of this complex. The nickel complex anion has good planarity and lies on a crystallographic inversion centre. There is disorder in the two terminal C atoms of two of the butyl chains of the tetra-n-butylammonium cation, the N atom of which is located on a twofold axis.

Journal Article↗
PubMed2002

One-step concentration of analytes based on dynamic change in pH in capillary zone electrophoresis.

A novel strategy for one-step concentration of analytes during capillary electrophoresis (CE) is presented. A short platinum wire was inserted into the 75-microm-i.d. separation capillary. When a high voltage was applied for CE separation, a sharp pH gradient along the capillary was created dynamically by the electrolysis of water in the running buffer. Concentration of a large volume of injected analytes was accomplished by the change in analyte charge due to the dynamic pH gradient. Depending on the polarity of the applied potential and the direction of electroosmotic flow, either anions or cations can be concentrated. Several hundredfold concentration factors were achieved. Fluorescence imaging by a CCD camera was used to monitor 10 cm of the capillary near the platinum wire during the concentration process. The observations are consistent with a sweeping mechanism.

Electrophoresis, Capillary↗
PubMed2002

Two-color excitation system for fluorescence detection in DNA sequencing by capillary array electrophoresis.

Two computer-controlled galvanometer scanners are adapted for two-dimensional step scanning across a 96-capillary array for laser-induced fluorescence detection. 488 nm and 514 nm laser lines from the same Ar(+) laser were alternately coupled for two-color excitation in each capillary. The signal at a single photomultiplier tube is temporally sorted to distinguish among the capillaries and the excitation wavelengths. Based on the differences in absorption spectra for the dyes, the peak-height ratios in the 488 nm and 514 nm excitation electropherograms were used for peak identification for multiplexed capillary electrophoresis. Successful base calling for 24-capillary DNA sequencing was achieved to 450 bp with 99% accuracy. Advantages include the efficient utilization of light due to the high duty-cycle of step scan, good detection performance due to the reduction of stray light, ruggedness due to the small mass of the galvanometer mirror, low cost due to the simplicity of components and flexibility due to the independent paths for excitation and emission.

Color↗