Two-dimensional protein database of human pancreas

We report here the two-dimensional protein database of human pancreas. The proteins were analyzed by two-dimensional electrophoresis followed by matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS). Totally, 302 proteins were identified, of which about 27% were enzymes with a broad range of catalytic activities. Several of these are specifically expressed in pancreas, such as pancreatic amylase, pancreatic stone protein, pancreatitis-associated protein, pancreatic lipase, pancreatic elastase, etc. Structural and cytoskeletal proteins are also strongly represented on the gels. Thus, the pancreatic proteome reflects the organ's function. This work paves the way for further studies on pancreatic protein expression in health and disease, such as diabetes and pancreatic cancer.     

Photo-and Electro-luminescence of the New Ternary Europium(III) Complex

In recent years, the interest in developing luminescent lanthanide complexes has been greatly stimulated by their potential use in electroluminescent displays1. Europium complexes appear most attractive in view of the high photoluminescent efficiency and the high monochromatic red light that are widely exploited in full-color displays2. It has been approved that the second ligand plays an important role in europium complexes, the synergistic complexation of the second ligand can not only lead …     

Simulation of water cluster assembly on a graphite surface

The assembly of small water clusters (H2O)n, n = 1-6, on a graphite surface is studied using a density functional tight-binding method complemented with an empirical van der Waals force correction, with confirmation using second-order M?ller-Plesset perturbation theory. It is shown that the optimized geometry of the water hexamer may change its original structure to an isoenergy one when interacting with a graphite surface in some specific orientation, while the smaller water cluster will maintain its cyclic or linear configurations (for the water dimer). The binding energy of water clusters interacting with graphite is dependent on the number of water molecules that form hydrogen bonds, but is independent of the water cluster size. These physically adsorbed water clusters show little change in their IR peak position and leave an almost perfect graphite surface.     

Synthesis of silk-like FeS2/NiS2 hybrid nanocrystals with improved reversible oxygen catalytic performance in a Zn-air battery

The development of highly active and stable reversible oxygen electrocatalysts is crucial for improving the efficiency of metal-air battery devices. Herein, an efficient liquid exfoliation strategy was designed for producing silk-like FeS₂/NiS₂ hybrid nanocrystals with enhanced reversible oxygen catalytic performance that displayed excellent properties for Zn-air batteries. Because of the unique silk-like morphology and interface nanocrystal structure, they can catalyze the oxygen evolution reaction (OER) efficiently with a low overpotential of 233 mV at j = 10 mA cm^?2. This is an improvement from the recently reported catalysts in 1.0 M KOH. Meanwhile, the oxygen reduction reaction (ORR) activity of the silk-like FeS₂/NiS₂ hybrid nanocrystals showed an onset potential of 911 mV and a half-wave potential of 640 mV. In addition, the reversible oxygen electrode activity of the silk-like FeS₂/NiS₂ hybrid nanocrystals was calculated to be 0.823 V, based on the potential of the OER and ORR. Further, the homemade rechargeable Zn-air batteries using FeS₂/NiS₂ hybrid nanocrystals as the air-cathode displayed a high open-circuit voltage of 1.25 V for more than 17 h and an excellent rechargeable performance for 25 h. The solid Zn-air batteries exhibited an excellent rechargeable performance for 15 h. This study provided a new method for designing interface nanocrystals with a unique morphology for efficient multifunctional electrocatalysts in electrochemical reactions and renewable energy devices.     

Chaotic micromixers using two-layer crossing channels to exhibit fast mixing at low Reynolds numbers

We report two chaotic micromixers that exhibit fast mixing at low Reynolds numbers in this paper. Passive mixers usually use the channel geometry to stir the fluids, and many previously reported designs rely on inertial effects which are only available at moderate Re. In this paper, we propose two chaotic micromixers using two-layer crossing channels. Both numerical and experimental studies show that the mixers are very efficient for fluid manipulation at low Reynolds numbers, such as stretching and splitting, folding and recombination, through which chaotic advection can be generated and the mixing is significantly promoted. More importantly, the generation of chaotic advection does not rely on the fluid inertial forces, so the mixers work well at very low Re. The mixers are benchmarked against a three-dimensional serpentine mixer. Results show that the latter is inefficient at Re = 0.2, while the new design exhibits rapid mixing at Re = 0.2 and at Re of O(10(-2)). The new mixer design will benefit various microfluidic systems.     

Efficient synthesis of complex glycopeptides based on unprotected oligosaccharides

N-Glycopeptides containing 1 to 4 trisaccharide chains, with the carbohydrates vicinal to each other in the multivalent glycopeptides, were efficiently synthesized by using the glycosylated Fmoc-asparagine as a key building block. While the couplings of amino acids with glycopeptides could be achieved in the homogeneous solutions in N-methylpyrrolidinone (NMP) to give excellent yields, all products were conveniently isolated from the reaction mixtures through a precipitation method by using the free carbohydrate chains as phase tags. Commercially available pentafluorophenyl (Pfp) esters of amino acids were employed for the glycopeptide elongation. Longer glycopeptides were constructed by means of a highly convergent synthetic design that is based on the coupling of glycopeptide/peptide fragments. Hydrogen bond interactions between free oligosaccharides were proposed to explain the exceptionally high efficiency of the couplings between two glycosylated building blocks.     

An evaluation of exogenous application of protoporphyrin IX and its dimethyl ester as a photodynamic diagnostic agent in poorly differentiated human nasopharyngeal carcinoma

5-Aminolevulinic acid and its esterified analogues have been under much investigation to enhance the endogenous production of protoporphyrin IX (PpIX) in tumor cells. However, in this work, we studied the in vitro and in vivo efficacy of exogenously administered PpIX and its esterified analogue, PpIX dimethyl ester (PME), in poorly differentiated human nasopharyngeal carcinoma (NPC/CNE-2) as a photodynamic diagnostic (PDD) agent. NPC/CNE-2 at its earliest time, 1 h after incubation with PME in in vitro studies, has exhibited 64% (P <0.01) higher tumor to normal cell (T/N) fluorescence ratio than with PpIX. In an in vivo mouse xenograft model, comparable photosensitizer concentration in tumor after intravenous administration was observed at 1-3 h time points, but at 9 h, PME had 31% (P=0.05) greater concentration in tumor compared with PpIX. In addition, by constituting PME and PpIX in different topical gel composites, of which, PME gel composition of 8:2 Plasdone and Gantrez resulted in the highest T/N ratio at 6 h after application (34%; P <0.05) in comparison with other gel composites. Evaluation of PME and PpIX constituted in the delivery vehicles investigated showed comparable selectivity for tumor at 1-3 h, thus neither photosensitizer is more efficient than the other for PDD at the early time points; however, beyond 6 h, PME had higher selectivity for tumor compared with PpIX. Thus, further investigation is warranted to improve the drug delivery vehicle for greater tumor selectivity at a shorter incubation time.     

Photocatalytic degradation of methylene blue on Fe3+-doped TiO2 nanoparticles under visible light irradiation

Fe³⁺-doped TiO₂ composite nanoparticles with different doping amounts were successfully synthesized using sol-gel method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and ultravioletvisible spectroscopy (UV-Vis) diffuse reflectance spectra (DRS). The photocatalytic degradation of methylene blue was used as a model reaction to evaluate the photocatalytic activity of Fe³⁺/TiO₂ nanoparticles under visible light irradiation. The influence of doping amount of Fe³⁺ (ω: 0.00%–3.00%) on photocatalytic activities of TiO₂ was investigated. Results show that the size of Fe³⁺/TiO₂ particles decreases with the increase of the amount of Fe³⁺ and their absorption spectra are broaden and absorption intensities are also increased. Doping Fe³⁺ can control the conversion of TiO₂ from anatase to rutile. The doping amount of Fe³⁺ remarkably affects the activity of the catalyst, and the optimum efficiency occurs at about the doping amount of 0.3%. The appropriate doping of Fe³⁺ can markedly increase the catalytic activity of TiO₂ under visible light irradiation. __________ Translated from Journal of Northwest Normal University (Natural Science), 2006, 42(6): 55–56 [译自: 西北师范大学学报(自然科学版)]     

A Minor New Flavone from Scutellaria baicalensis Georgi

A new flavone,6,2′-dihydroxy-5,7,8,6′-tetramethoxyflavone,was isolated from the roots of Scutellaria baicalensis. Its structure was established on the basis of spectral evidences.