Low-Temperature Synthesis of Anatase TiO2 Nanoparticles with Tunable Surface Charges for Enhancing Photocatalytic Activity

In this work, the positively or negatively charged anatase TiO₂ nanoparticles were synthesized via a low temperature precipitation-peptization process (LTPPP) in the presence of poly(ethyleneimine) (PEI) and poly(sodium4- styrenesulfonate) (PSS). X-ray diffraction (XRD) pattern and high-resolution transmission electron microscope (HRTEM) confirmed the anatase crystalline phase. The charges of the prepared TiO₂, PEI-TiO₂ and PSS-TiO₂ nanoparticles were investigated by zeta potentials. The results showed that the zeta potentials of PEI-TiO₂ nanoparticles can be tuned from +39.47 mV to +95.46 mV, and that of PSS-TiO₂ nanoparticles can be adjusted from −56.63 mV to −119.32 mV. In comparison with TiO₂, PSS-TiO₂ exhibited dramatic adsorption and degradation of dye molecules, while the PEI modified TiO₂ nanoparticles showed lower photocatalytic activity. The photocatalytic performances of these charged nanoparticles were elucidated by the results of UV-vis diffuse reflectance spectra (DRS) and the photoluminescence (PL) spectra, which indicated that the PSS-TiO₂ nanoparticles showed a lower recombination rate of electron-hole pairs than TiO₂ and PEI-TiO₂.     

Nanoparticles of Polyethylene Sebacate: A New Biodegradable Polymer

The present study demonstrates feasibility of preparation of nanoparticles using a novel polymer, polyethylene sebacate (PES), and its application in the design of drug-loaded nanocarriers. Silymarin was selected as a model hydrophobic drug for the present study. Two methods of preparation, viz., nanoprecipitation and emulsion solvent diffusion, were evaluated for preparation of nanoparticles. Effect of surfactants polyvinyl alcohol (PVA), lutrol F 68, and Tween 80 on the preparation of blank and silymarin-loaded PES nanoparticles was evaluated. Nanoprecipitation resulted in the formation of nanoparticles with all the surfactants (<450 nm). Increase in surfactant concentration resulted in decrease in entrapment efficiency and particle size except with PVA. The type and concentration of surfactant was critical to achieve low size and adequate drug entrapment. While increase in concentration of PES resulted in larger nanoparticles, inclusion of acetone in the organic phase resulted in particles of smaller size. In case of emulsion solvent diffusion, nanoparticles were obtained only with lutrol F 68 as surfactant and high surfactant concentration. The study revealed nanoprecipitation as a more versatile method for preparation of PES nanoparticles. Scanning electron microscopy studies revealed spherical shape of nanoparticles. Freeze-dried nanoparticles exhibited ease of redispersion, with a marginal increase in size. Differential scanning calorimetry and X-ray diffraction analysis revealed amorphous nature of the drug. The study demonstrates successful design of PES nanoparticles as drug carriers.     

Interrogation of a Sonogashira Cross-Coupling of 8-Bromoguanosine with Phenylacetylene on Amberlite: Evidence for Pd/Cu Ion Binding and Propagation of Pd/Cu Nanoparticles

The reactivity of Amberlite (IRA-67) base “heterogeneous” resin in Sonogashira cross-coupling of 8-bromoguanosine 1 with phenylacetylene 3 to give 2 has been examined. Both 1 and 2 coordinate to Pd and Cu ions, which explains why at equivalent catalyst loadings, the homogeneous reaction employing triethylamine base is poor yielding. X-ray photo-electron spectroscopy (XPS) has been used to probe and quantify the active nitrogen base sites of the Amberlite resin, and postreaction Pd and Cu species. The PdCl₂(PPh₃)₂ precatalyst and CuI cocatalyst degrade to give Amberlite-supported metal nanoparticles (average size ～2.7 nm). The guanosine product 2 formed using the Amberlite Pd/Cu catalyst system is of higher purity than reactions using a homogeneous Pd precatalyst, a prerequisite for use in biological applications.     

原核启动子识别研究进展

原核启动子识别是研究原核基因转录调控的重要环节。该文以大肠杆菌为例,首先介绍原核启动子的基本特征,再对已有的各种识别方法进行具体分析,最后探讨可能的改进方向。     

Supported Palladium Nanoparticles Synthesized by Living Plants as a Catalyst for Suzuki-Miyaura Reactions

The metal accumulating ability of plants has previously been used to capture metal contaminants from the environment; however, the full potential of this process is yet to be realized. Herein, the first use of living plants to recover palladium and produce catalytically active palladium nanoparticles is reported. This process eliminates the necessity for nanoparticle extraction from the plant and reduces the number of production steps compared to traditional catalyst palladium on carbon. These heterogeneous plant catalysts have demonstrated high catalytic activity in Suzuki coupling reactions between phenylboronic acid and a range of aryl halides containing iodo-, bromo- and chloro- moieties.     

与结瘤基因nodF的启动子相互重叠的启动子起始一个RNA分子的转录(英文)

在根瘤菌中 ,结瘤基因的表达受到转录水平上复杂的调控。通过体外转录、引物延伸等一系列实验在豌豆根瘤菌中发现一个与结瘤基因nodF的启动子相互重叠 ,但转录方向相反的启动子 ,该启动子特异起始一个新的RNA分子———px2 的转录。Northern印迹确定 px2 的长度为 0 .72kb ,并且证明 px2 的转录是依赖于根瘤菌的与E .coliσ70 同源的sigma因子。px2的转录启始位点在体内、体外均相同 ,它坐落在结瘤基因顺式元件的“nodbox”内。进一步发现 px2 的体外转录受到一个参与结瘤基因调控的蛋白———Px的抑制。有结果显示 ,px2 影响结瘤基因的表达     

Doped Natural Phosphate: A New and Environmentally Friendly Catalyst in Nucleoside Synthesis

Abstract

Doped natural phosphate is used as acidic or basic catalyst in nucleoside and acyclonucleoside synthesis. Some examples are given.     

基于二次判别的果蝇启动子识别

通过对果蝇polⅡ启动子和非启动子的序列特征分析,计算了序列每个位点单碱基保守性M1(l)值和六联体保守性M6(l)值。从而分别选取两个区域的六联体频数作为离散源参数,利用离散增量结合二次判别函数(IDQD)对启动子进行了预测。对于从编码区和内含子中选取的非启动子数据集,启动子的预测成功率分别达到93%和89%。比较结果显示IDQD模型能够有效地提高启动子预测成功率。     

A New Method of Preparing Ca2+-ATPase from Sarcoplasmic Reticulum: Extraction with Octylglucoside

A fast method for preparing Ca²⁺-ATPase from rabbit muscle sarcoplasmic reticulum was devised. The method involves extracting extrinsic membrane proteins with the non-ionic detergent octylglucoside at high salt concentration. A Ca²⁺ ATPase of consistently high specific activity (about 25 μmoles/mg·min) is found in the insoluble residue. The method was optimized with respect to the concentrations of detergent and salt, pH, and other extraction conditions. By the criteria of the protein pattern in SDS-polyacrylamide gel electrophoresis, dependence of the hydrolytic activity on the presence of Ca²⁺, and the phosphoprotein formation, the preparation is identical with the Ca²⁺-ATPase isolated previously by MacLennan [10] and other authors. The main advantages of the new method are its rapidity, its reliability, and the high specific activity of the purified enzyme.     

THDP17 Decreases Ammonia Production through Glutaminase Inhibition. A New Drug for Hepatic Encephalopathy Therapy

Ammonia production is implicated in the pathogenesis of hepatic encephalopathy (HE), being intestinal glutaminase activity the main source for ammonia. Management of ammonia formation can be effective in HE treatment by lowering intestinal ammonia production. The use of glutaminase inhibitors represents one way to achieve this goal. In this work, we have performed a search for specific inhibitors that could decrease glutaminase activity by screening two different groups of compounds: i) a group integrated by a diverse, highly pure small molecule compounds derived from thiourea ranging from 200 to 800 Daltons; and ii) a group integrated by commonly use compounds in the treatment of HE. Results shown that THDP-17 (10 µM), a thiourea derivate product, could inhibit the intestinal glutaminase activity (57.4±6.7%). Inhibitory effect was tissue dependent, ranging from 40±5.5% to 80±7.8% in an uncompetitive manner, showing V_max and K_m values of 384.62 µmol min⁻¹, 13.62 mM with THDP-17 10 µM, respectively. This compound also decreased the glutaminase activity in Caco-2 cell cultures, showing a reduction of ammonia and glutamate production, compared to control cultures. Therefore, the THDP-17 compound could be a good candidate for HE management, by lowering ammonia production.     

A Sequential Vesicle Pool Model with a Single Release Sensor and a Ca2+-Dependent Priming Catalyst Effectively Explains Ca2+-Dependent Properties of Neurosecretion

Neurotransmitter release depends on the fusion of secretory vesicles with the plasma membrane and the release of their contents. The final fusion step displays higher-order Ca²⁺ dependence, but also upstream steps depend on Ca²⁺. After deletion of the Ca²⁺ sensor for fast release – synaptotagmin-1 – slower Ca²⁺-dependent release components persist. These findings have provoked working models involving parallel releasable vesicle pools (Parallel Pool Models, PPM) driven by alternative Ca²⁺ sensors for release, but no slow release sensor acting on a parallel vesicle pool has been identified. We here propose a Sequential Pool Model (SPM), assuming a novel Ca²⁺-dependent action: a Ca²⁺-dependent catalyst that accelerates both forward and reverse priming reactions. While both models account for fast fusion from the Readily-Releasable Pool (RRP) under control of synaptotagmin-1, the origins of slow release differ. In the SPM the slow release component is attributed to the Ca²⁺-dependent refilling of the RRP from a Non-Releasable upstream Pool (NRP), whereas the PPM attributes slow release to a separate slowly-releasable vesicle pool. Using numerical integration we compared model predictions to data from mouse chromaffin cells. Like the PPM, the SPM explains biphasic release, Ca²⁺-dependence and pool sizes in mouse chromaffin cells. In addition, the SPM accounts for the rapid recovery of the fast component after strong stimulation, where the PPM fails. The SPM also predicts the simultaneous changes in release rate and amplitude seen when mutating the SNARE-complex. Finally, it can account for the loss of fast- and the persistence of slow release in the synaptotagmin-1 knockout by assuming that the RRP is depleted, leading to slow and Ca²⁺-dependent fusion from the NRP. We conclude that the elusive ‘alternative Ca²⁺ sensor’ for slow release might be the upstream priming catalyst, and that a sequential model effectively explains Ca²⁺-dependent properties of secretion without assuming parallel pools or sensors.     

A Comparison of Low-Temperature and Ambient-Temperature SEM for Viewing Nematode Faces

Faces of lesion nematodes Pratylenchus teres (populations RTB and JK) and P. zeae or the bacterivore Distolabrellus veechi were observed on frozen specimens with low-temperature scanning electron microscopy and as chemically fixed, critical-point dried specimens with conventional scanning electron microscopy. Amphidial secretions were preserved in chemically fixed but not cryofixed lesion nematodes. Overhanging liplets of chemically fixed D. veechi may be artifactual because they appeared as variably filled, mostly empty membranes when cryofixed. The diagnostically useful lips of the frozen lesion nematodes exhibited six sectors of variable prominence that were absent in chemically fixed specimens. This variability may be due to different degrees of muscle contraction captured during cryofixation, which occurs in milliseconds. This is the first evidence that rarely observed lip sectors in Pratylenchus may be something other than an artifact of shrinkage.     

A New lncRNA,APTR, Associates with and Represses the CDKN1A/p21 Promoter by Recruiting Polycomb Proteins

Long noncoding RNAs (lncRNAs) have emerged as a major regulator of cell physiology, but many of which have no known function. CDKN1A/p21 is an important inhibitor of the cell-cycle, regulator of the DNA damage response and effector of the tumor suppressor p53, playing a crucial role in tumor development and prevention. In order to identify a regulator for tumor progression, we performed an siRNA screen of human lncRNAs required for cell proliferation, and identified a novel lncRNA, APTR, that acts in trans to repress the CDKN1A/p21 promoter independent of p53 to promote cell proliferation. APTR associates with the promoter of CDKN1A/p21 and this association requires a complementary-Alu sequence encoded in APTR. A different module of APTR associates with and recruits the Polycomb repressive complex 2 (PRC2) to epigenetically repress the p21 promoter. A decrease in APTR is necessary for the induction of p21 after heat stress and DNA damage by doxorubicin, and the levels of APTR and p21 are anti-correlated in human glioblastomas. Our data identify a new regulator of the cell-cycle inhibitor CDKN1A/p21 that acts as a proliferative factor in cancer cell lines and in glioblastomas and demonstrate that Alu elements present in lncRNAs can contribute to targeting regulatory lncRNAs to promoters.     

A New Proposal for Highly Sensitive Refractive Index Sensor Using Vertically Coupled Plasmonic Elliptic-Disk up Elliptic-Ring Nanoparticles

Plasmonics - In this research work, a novel highly sensitive refractive index sensor using Au and Ag elliptic-shaped nanoparticles are proposed. The main idea of this work is using an original...