Charge transfer dynamics of 3,4,9,10-perylene-tetracarboxylic-dianhydride molecules on Au(111) probed by resonant photoemission spectroscopy

Charge transfer dynamics across the lying-down 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) organic semiconductor molecules on Au(111) interface has been investigated using the core-hole clock implementation of resonant photoemission spectroscopy. It is found that the charge transfer time scale at the PTCDA∕Au(111) interface is much larger than the C 1s core-hole lifetime of 6 fs, indicating weak electronic coupling between PTCDA and the gold substrate due to the absence of chemical reaction and∕or bonding.     

A perturbation analysis of rate theory of self-regulating genes and signaling networks

A thorough kinetic analysis of the rate theory for stochastic self-regulating gene networks is presented. The chemical master equation kinetic model in terms of a coupled birth-death process is deconstructed into several simpler kinetic modules. We formulate and improve upon the rate theory of self-regulating genes in terms of perturbation theory. We propose a simple five-state scheme as a faithful caricature that elucidates the full kinetics including the "resonance phenomenon" discovered by Walczak et al. [Proc. Natl. Acad. Sci. U.S.A. 102, 18926 (2005)]. The same analysis can be readily applied to other biochemical networks such as phosphorylation signaling with fluctuating kinase activity. Generalization of the present approach can be included in multiple time-scale numerical computations for large biochemical networks.     

固相萃取-液相色谱-质谱/质谱法同时测定蜂蜜中的多类药物残留

建立了采用固相萃取-液相色谱-质谱/质谱(SPE-LC-MS/MS)对蜂蜜中磺胺类、硝基咪唑类、喹诺酮类、大环内酯类、林可酰胺类和吡喹酮共计6大类54种药物残留同时测定的方法。蜂蜜经磷酸盐缓冲溶液(pH 8)稀释,Oasis HLB固相萃取柱净化后,通过液相色谱-质谱联用技术进行检测(正离子方式,多反应监测模式)。采用同位素稀释内标法或外标法进行定量,线性关系良好,相关系数大于0.992。方法的定量限(LOQ,以信噪比(S/N)大于10计)分别为磺胺类和硝基咪唑类药物1.0 μg/kg,喹诺酮类和林可酰胺类药物2.0 μg/kg,大环内酯类药物3.0 μg/kg,吡喹酮0.3 μg/kg。总体回收率为32.6%～114%,相对标准偏差为1.3%～28.9%。该方法的定量限满足目前国内外药物的最大残留限量要求,可作为蜂蜜中相关药物残留量的筛选检测方法。     

超高效液相色谱-电喷雾三重四极杆质谱法测定中药中马兜铃酸A和B的含量

利用超高效液相色谱-电喷雾三重四极杆质谱仪建立了中药中马兜铃酸A和B的定性定量分析方法。选取柴胡、生甘草、桔梗、龙胆泻肝丸、消胖丸、减肥茶等14种代表性样品,用甲醇-水(70:30, v/v)溶液加热回流提取,经Oasis MAX固相萃取柱富集净化后,在Eclipse RP HD C18反相柱(150 mm×2.1 mm, 1.8 μm)上进行分离;流动相为5 mmol/L乙酸铵水溶液(pH 7.5)-乙腈(75:25, v/v)。采用电喷雾离子源正离子模式(ESI+)和多反应监测模式(MRM)进行质谱分析。马兜铃酸A和B的线性范围分别为0.5～200 μg/L和1～200 μg/L,相关系数(r2)均大于0.995;检出限(LODs)分别为5 μg/kg和7.5 μg/kg;定量限(LOQs)分别为12.5 μg/kg和25 μg/kg。在100 μg/kg和500 μg/kg添加水平下,马兜铃酸A和B的回收率(n=6)范围分别为60.3%～96.4%和61.3%～94.7%,相对标准偏差均不大于10.2%。该方法灵敏度高,重复性好,操作简便,适用于中药材、饮片及中成药中马兜铃酸A和B的痕量检测。     

基质固相分散萃取-高效液相色谱-串联质谱法分析拟南芥中的赤霉素

建立了基质固相分散萃取-高效液相色谱-串联质谱法(MSPD-HPLC-MS/MS)同时测定拟南芥中3种赤霉素GA1, GA3和GA4的分析方法。将拟南芥样品与C18填料混合研磨制成MSPD柱,并采用80%冷甲醇洗脱。采用反相C18色谱柱进行分离,以0.05%甲酸水溶液和乙腈为流动相进行梯度洗脱,采用电喷雾离子源负离子模式(ESI~)电离,多反应监测模式检测。对样品前处理条件、色谱分离条件和质谱检测条件进行了优化,结果表明,在最优条件下,3种赤霉素在10～300 ng/g范围内均呈良好线性关系,相关系数(r2)均大于0.98,检出限在1.1～4.1 ng/g之间。在10～50 ng/g添加水平下,平均回收率范围为54.7%～102.6%,相对标准偏差（RSD,n=3)为3.2%～12.8%。该方法操作简单、灵敏度高、选择性好、回收率高,适合拟南芥中GA1、GA3、GA4含量的测定。     

氧化铝负载Co基F-T合成催化剂还原性能

采用XRD、TPR、XPS和H2-TPD等技术对Co/Al2O3催化剂的还原性能进行了研究.还原温度低时,催化剂中Co物种还原不充分,活化不够,催化剂的F-T合成反应活性偏低;高温还原时,由于催化剂中金属钴颗粒聚集和增大使活性组分的有效活性面积减小,催化剂的F-T合成反应活性下降.还原温度在400～500℃之间存在最佳...     

Peroxyoxalate Chemiluminescence Based on Fluorescent Conjugated Polymer for the Determination of Triton X-100

A novel peroxyoxalate chemiluminescence system has been designed for the determination of Triton X‐100 (TX‐100), in which a hydrophobic fluorescent conjugated polymer, poly[2,5‐bisnonyloxy‐1,4‐phenylene‐ethynylene‐9,10‐anthrylene] (PPEA) was employed as a fluorophor. A strong enhanced intensity of chemiluminescence (CL) was observed in the presence of TX‐100, due to the improved emission efficiency of PPEA in the presence of TX‐100. Under optimum conditions, the detection range of Triton X‐100 is between 1.0×10^?7 and 1.0× 10^?4 mol·L^?1, with a detection limit at 6.0×10^?8 mol·L^?1. The relative standard deviation is 2.4% (n=6) for 1.0×10^?6 mol·L^?1 Triton X‐100. This method provides satisfying results in the detection of TX‐100 in nature water and biological samples with high sensitivity and wide linear range.     

Convenient Synthesis of 3,5‐Biscarbamoyl‐pyridine Derivatives

An efficient and convenient method for synthesis of 3,5‐bis‐carbamoyl‐2,6‐dimethylpyridine derivatives was achieved in good to excellent yields by reaction of anilines with 3,5‐bis(3′,5′‐dimethyl‐1′‐pyrazolyl‐carbonyl)‐2,6‐dimethylpyridine, in which pyrazoles served as leaving groups. The structures of products were confirmed by spectra data and microanalysis.     

Synthesis of 1‐Aryl‐1H‐indazoles via a Ligand‐Free Copper‐ Catalyzed Intramolecular Amination Reaction

A general synthesis of 1‐aryl‐1‐H‐indazoles from o‐halogenated aryl aldehydes or ketones and aryl hydrazines was described. This protocol included an intermolecular condensation and a ligand‐free copper‐catalyzed intramolecular Ullmann‐type coupling reaction. This method was applied to a wide range of substrates to produce the indazole products in good yields.     

对甲苯磺酰氯催化的meso-四芳基卟啉的合成

报道了一种改进了的meso-四芳基卟啉合成方法.利用对甲苯磺酰氯催化吡咯和芳香醛缩合生成中间物卟啉原,卟啉原中间物在紫外光照射下被空气氧化生成四芳基卟啉.该方法所用催化剂价廉易得,氧化过程绿色.整体反应条件简单,易于操作,产率高.