Growth and surface characterization of sputter-deposited molybdenum oxide thin films

Molybdenum oxide thin films were produced by magnetron sputtering using a molybdenum (Mo) target. The sputtering was performed in a reactive atmosphere of an argon-oxygen gas mixture under varying conditions of substrate temperature (T_s) and oxygen partial pressure (pO₂). The effect of T_s and pO₂ on the growth and microstructure of molybdenum oxide films was examined in detail using reflection high-energy electron diffraction (RHEED), Rutherford backscattering spectrometry (RBS), energy-dispersive X-ray spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) measurements. The analyses indicate that the effect of T_s and pO₂ on the microstructure and phase of the grown molybdenum oxide thin films is remarkable. RHEED and RBS results indicate that the films grown at 445 °C under 62.3% O₂ pressure were stoichiometric and polycrystalline MoO₃. Films grown at lower pO₂ were non-stoichiometric MoO_x films with the presence of secondary phase. The microstructure of the grown Mo oxide films is discussed and conditions were optimized to produce phase pure, stoichiometric, and highly textured polycrystalline MoO₃ films.     

Reaction kinetics of the selective liquid phase hydrogenation of styrene oxide to β-phenethyl alcohol

Liquid phase hydrogenation of styrene oxide using 1% Pd/C and NaOH as a promoter was found to give selectively β-phenethyl alcohol (PEA) under very mild conditions (313–333 K; 0.68–5.5 MPa). The kinetics of this system was investigated by collecting initial rate data in a batch slurry reactor. Rate of hydrogenation was found to decrease beyond a certain concentration of both hydrogen (>3 MPa) and styrene oxide (>0.5 kmol/m³). A Langmuir–Hinshelwood type rate equation has been proposed based on the initial rate data in the kinetic regime. The model predictions agree very well with the experimentally observed concentration–time data indicating the applicability of the proposed rate model.     

Amperometric Detection of Catechol and Catecholamines by Immobilized Laccase from DeniLite

DeniLite laccase immobilized Pt electrode was used for detection of catechol and catecholamines. The enzymatically oxidized substrates were measured amperometrically. The sensitivities are 210, 75, 60 and 45 nA/μM with the upper limits of linear ranges of 58, 40, 55 and 55 μM and the detection limits (S/N=3) of 0.07, 0.2, 0.3 and 0.4 μM for catechol, dopamine (DA), norepinephrine (NEPI) and epinephrine (EPI), respectively. The response time (t_90%) is about 2 seconds for each substrate and the long‐term stability is around 40–50 days with retaining 80% of initial activity. The very fast response and the remarkable long‐term stability are the principal advantages of this sensor. In case of catechol, the pH response of the sensor is mainly determined by enzyme's pH profile, however, in case of catecholamines, both enzyme's pH profile and reversibility of the substrate are operated and the optimal pHs for NEPI and EPI shift towards acidic range compared to that for DA. The presence of ascorbic acid (<50 μM) did not interfere with the measurement.     

多级结构Ni@CuS复合物的合成及在提高催化还原4-硝基苯酚性能方面的应用

三种多级结构花状硫化铜通过水热法,利用纳米薄片自组装形成.加入有机分子聚乙烯吡咯烷酮或1, 3, 5-均苯三甲酸调控其片层密度.产物作为基板生长镍纳米颗粒.通过环境扫描电子显微镜(SEM), X射线衍射(XRD),透射电子显微镜(TEM)等对这种复合物的结构进行表征.利用紫外-可见吸收光谱,研究了产物作为催化剂催化还原4-硝基苯酚的性能.结果表明,长在具有最稀疏片层的样品(Ni@SUB2)上的镍纳米颗粒(NiNPs,直径5 nm左右)具有超低负载量,为0.469% (w). Ni@SUB2在三种Ni@SUB复合物中具有最好的催化性能.还原4-硝基苯酚的反应中, 4-硝基酚初始浓度为0.2 mmol·L^-1时Ni@SUB2在4 min中内转化率可以实现100%,而等量的纯Ni纳米颗粒转化率只有43%.增强的催化性能可以归结为镍纳米颗粒在硫化铜基板上得到良好分散,可以提供更多催化位点.同时硫化铜基板不溶于水,可以通过离心的方式回收催化剂,有利于环境保护.     

植物体系中甲酯酶的底物专一性的理论研究

酶对天然底物的高度专一性是酶的特点之一. 然而关于酶是如何对底物具有高度专一性以及识别能力, 我们的理解仍然缺乏. 本文以植物体系中发现的一组甲酯酶(MESs)对一些底物[包括水杨酸甲酯(MeSA), 茉莉酮酸甲酯(MeJA)和吲哚-3-乙酸甲酯(MeIAA)]的催化反应为例, 报道了同源建模和理论计算对茉莉酮酸甲酯酶(AtMES10)和水杨酸结合蛋白2(SABP2)的研究结果. 基于简单的锁-钥匙理论(底物与酶结合时不发生基团的碰撞或严重排斥), 以底物对接到酶的活性部位(即底物中—COO的一部分占据可被催化丝氨酸亲核进攻的位置) 为原则, 可以在空间上为酶对底物的专一性提供解释. 模拟结果表明, SABP2可对MeSA有高活性, 对MeJA和MeIAA有低或无活性; AtMES10可对MeJA有高活性, 而对MeSA和MeIAA有低或无活性, 这与实验结果相一致. 因此, 相关酶的结构预测与计算机模拟对了解酶的底物专一性具有重要的意义.     

Isolation of New Polyketide Synthase Gene Fragments and a Partial Gene Cluster from East China Sea and Function Analysis of a New Acyltransfrase

Using the consensus-degenerate hybrid oligonucleotide primer polymerase chain reaction method, 26 new ketoacyl synthase (KS) fragments were isolated from a marine sediment sample in the East China Sea (ECS) and analyzed by construction of a phylogenetic tree. With a digoxigenin-labeled KS gene fragment used as a probe, a partial polyketide synthase (PKS) gene cluster was isolated and identified by hybridization screening of a marine sediment sample metagenome fosmid library constructed for this study. A new acyltransferase (AT) gene was cloned from the PKS gene cluster and heterogeneously expressed as a protein fused to maltose-binding protein (MBP). Ultraviolet spectrophotometry was used to study the binding of the MBP–AT fusion protein and single AT domain to substrates using MBP and bovine serum albumin as control proteins. Binding constants (Ka, per micromolar) were calculated and used to analyze the substrate specificity of the acyltransferase. We concluded that there are many unrevealed new PKS gene clusters in marine sediments in the ECS. The acyltransferase is presumably an acetyltransferase from a new PKS gene cluster.     

Novel bicyclisation of unsaturated polyols in PdCl2-CuCl2-AcOH catalytic system

Novel type of Pd(II)-catalysed transformation of sugar-derived alkenitols furnishing 7-benzyloxy-2,5-dioxabicyclo[2.2.1]heptanes was discovered. The investigated bicyclisation displays an exceptional substrate selectivity towards xylo-configured unsaturated polyols. Moreover, a newly build stereogenic centre is formed in a diastereospecific cis-manner. The observed stereochemical preference was corroborated by modelling of pertinent transition states at the semiempirical level of theory (PM5). In addition, the single crystal X-ray analysis of an acylated analogue d-glycero-l-gulo-21 was done in order to establish the relative configuration of related bicyclic products.     

Hydrophobically directed selective reduction of ketones using amine boranes

Amine boranes bearing hydrophobic substituents were used to reduce aryl ketones in competition with a methyl ketone. Their high stability in protic solvents combined with their ease of preparation made amine boranes useful compounds in the study of hydrophobically directed selective reductions. Several characteristics of the reducing agent were found to be important in determining the reaction selectivity, including available hydrocarbon surface area, degree of fluorination, and proximity of the hydrophobic group to the active hydrides.     

基体对流动锌酸钾碱液中锌电沉积的影响

在流动的高浓度锌酸钾碱液中研究了镍箔和镀镍冲孔钢带基体电极对锌沉积/溶解电化学行为的影响. 结果表明, 在流动电解液中电极表面浓度梯度变化不大, 不同基体上均未出现锌沉积的阴极峰; 扫描速度超过10 mV/s, 循环伏安曲线基本不随扫速变化, 说明锌的沉积/溶解峰电流不仅与扫描速度有关, 还取决于锌沉积的时间. 采用镀镍冲孔钢带基体兼有析氢过电位大和稳定性好的特点, 又由于其特殊的冲孔结构, 改变了传质方式, 锌沉积的极化降低, 孔的周围形成紧密堆积的沉积锌, 锌沉积的电流和电量大, 沉积效率高, 经 4次充放电循环后, 库仑效率即达95％以上, 是性能较佳的基体电极.     

Cyclin A-Cdk2 Phosphorylates BH3 only Protein Bad in vitro and in vivo

Increasing evidence suggests that Cyclin A-Cdk2 activity is required in the apoptosis process induced by various stimuli. To determine a specific substrate of Cyclin A-Cdk2 for apoptosis, in this study, we carried out anin vitro kinase assay using immunoprecipitated complex Cyclin A-Cdk2 as an enzyme source, and recombinant protein GST-Bad as a substrate. Our study showed that Bad was clearly phosphorylated by Cyclin A-Cdk2 in vitro. To examine whether protein Bad can also be phosphorylated by Cyclin A-Cdk2 kinase in vivo, we transiently overexpressed protein Bad with Cyclin A or Cdk2-dn, a dominant negative version of Cdk2, in Hela cells and determined the phosphorylation status of protein Bad. The test showed that protein Bad was clearly phosphorylated in Cyclin A overexpressed cells,but not in Cdk2-dn or mock transfectent. Moreover, etoposide also caused the phosphorylation of endogenetic Bad. In conclusion, here we provide first time evidence that protein Bad can be a substrate of Cyclin A-Cdk2 apoptosis for in vitro and in vivo.