A new method for determination of uric acid by the lactic acid-acetone-BrO(3)(-)-Mn(2+)-H(2)SO(4) oscillating reaction using the analyte pulse perturbation technique

A new analytical method for the determination of uric acid (UA) by the perturbation of UA on the Belousov-Zhabotinsky oscillating reaction is proposed. The method is based on the linear relationship between the changes in the oscillating period and the concentration of UA. The calibration curve is linear over the range of 2.0 × 10⁻⁵ to 5.0 × 10⁻⁴ M, with a detecting limit of 3.28 × 10⁻⁶ M. The method features good precision (R.S.D.: 3.59%) and excellent throughput (10 samples h⁻¹). The possible mechanism of the perturbation of UA on the oscillating reaction is discussed.     

线上线下混合式教学结合翻转课堂进行酯缩合反应的教学*

采用“线上线下混合式教学”开展有机化学课程的教学工作,利用APP “学习通”将在线课堂教学和线下讲授相结合。以知识点酯缩合反应的教学为例,介绍了该教学模式的实施过程和教学效果。实践结果表明,线上线下混合式教学与翻转课堂相结合的教学模式,能够拓展化学专业学生知识面,提升学生的自主学习能力和学习的积极性,取得了较好的教学效果。     

Metal-binding properties of the peptide APP170-188: a model of the ZnII-binding site of amyloid precursor protein (APP)

Amyloid precursor protein (APP) plays a key role in Alzheimer's disease (AD), although the function of this membrane protein is still unclear. Metal ions are implicated in AD and they also interact with APP. APP possesses a strong ZnII binding site, which is evolutionary conserved. In this paper a synthetic peptide, APP170-188, with a sequence corresponding to the conserved ZnII-binding domain of APP, was synthesised and its metal-binding properties analysed. Titration experiments pointed to the binding of a stoichiometric amount of divalent ions. Further studies indicated that the binding of divalent metals like ZnII, CdII and CoII induces the dimerisation of the peptide. This dimer contains a dinuclear cluster in which the two divalent metals are bridged by two thiolate ligands from cysteine residues. The other two ligands of the tetrahedral coordination sites of each metal ion are terminal thiolate ligands. This structure was supported by the following arguments. The complex formed with CoII presents the characteristic features for tetrahedral tetrathiolate coordination in its UV-visible spectrum. The sequence of APP170-188 contains only three cysteine residues, which is incompatible with a monomeric CoII-APP170-188 complex. EPR measurements of the complex with one equivalent of CoII show almost no signal at 4 K, which is compatible with an antiferromagnetic spin-coupling of the metal ions in a cluster structure. Size-exclusion chromatography indicated that the elution time for the complexes with ZnII and CdII corresponds to the expected molecular weight of a dimer. The circular dichroism (CD) spectrum of the complex with one equivalent of CdII shows a band at 265 nm+, and an ellipticity similar to those observed for similar CdII-thiolate clusters. Possible biological implications of the ZnII binding site and the metal-induced dimerisation are discussed.     

Competition between the albumin and three histidine fragment of amyloid precursor protein sites to bind Cu(II)

The aim of this work was to check experimentally the relationship between the five-nitrogen donor system {3 × N_imid, 2 × N⁻} seen e.g. in the peptide fragments of the cysteine-rich amyloid precursor protein (APP) region and the albumin-like {NH₂, 2 × N⁻, N_imid} coordination site. The protected and unprotected octadecapeptides DAHQERMDVSETHLHWHT and Ac-DAHQERMDVSETHLHWHT-NH₂ were synthesized and potentiometric and spectroscopic studies were performed. A comparison of both metal-binding sites that occur in both peptides clearly shows that in the unprotected ligand albumin-like binding is much more efficient than the three His site, although around pH 5 both sites have a comparable ability to bind the Cu(II) ion. However, a comparison of the protected and unprotected peptides with their metal binding sites clearly shows that the three His site is very efficient in binding Cu(II) although less effective than the albumin-like motif.     

基于TD-LTE短信平台的智能排队叫号系统设计

随着经济和社会的快速发展,服务行业的种类和业务量急剧增长,排队等候成为人们经常面临的问题。为了解决排队等候的秩序问题,智能排队叫号系统应运而生。本文设计了一种基于TD-LTE短信平台的智能排队叫号系统,该系统可以通过APP预约软件进行排号,也可以通过服务大厅的固定取号端进行排队取号,方便了人们办理各种业务,节省了排队时间。该系统采用了软硬件协同的方法进行设计,各模块之间使用无线方式进行连接,简化了布线的复杂性。该系统具有安装快捷,使用维护方便,成本低廉,便于扩展等特点。     

Detection and quantification of plasma amyloid-β by selected reaction monitoring mass spectrometry

Amyloid-β (Aβ) in human plasma was detected and quantified by an antibody-free method, selected reaction monitoring mass spectrometry (SRM-MS) in the current study. Due to its low abundance, SRM-based quantification in 10 μL plasma was a challenge. Prior to SRM analysis, human plasma proteins as a whole were digested by trypsin and high pH reversed-phase liquid chromatography (RPLC) was used to fractionate the tryptic digests and to collect peptides, Aβ_1–5, Aβ_6–16, Aβ_17–28 and Aβ_29–40(42) of either Aβ_1–40 or Aβ_1–42. Among those peptides, Aβ_17–28 was selected as a surrogate to measure the total Aβ level. Human plasma samples obtained from triplicate sample preparations were analyzed, obtaining 4.20 ng mL⁻¹ with a CV of 25.3%. Triplicate measurements for each sample preparation showed CV of <5%. Limit of quantification was obtained as 132 pM, which corresponded to 570 pg mL⁻¹ of Aβ_1–40. Until now, most quantitative measurements of Aβ in plasma or cerebrospinal fluid have required antibody-based immunoassays. Since quantification of Aβ by immunoassays is highly dependent on the extent of epitope exposure due to aggregation or plasma protein binding, it is difficult to accurately measure the actual concentration of Aβ in plasma. Our diagnostic method based on SRM using a surrogate peptide of Aβ is promising in that actual amounts of total Aβ can be measured regardless of the conformational status of the biomarker.     

Left APP differential polynomial rings

A ring R is called a left APP-ring if for each element a∈R, the left annihilator l_R(Ra) is right s-unital as an ideal of R or equivalently R∕l_R(Ra) is flat as a left R-module. In this paper, we show that for a ring R and derivation δ of R, R is left APP if and only if R is δ-weakly rigid and the differential polynomial ring R[x;δ] is left APP. As a consequence, we see that if R is a left APP-ring, then the n^th Weyl algebra over R is left APP. Also we define δ-left APP (resp. p.q.-Baer) rings and we show that R is left APP (resp. p.q.-Baer) if and only if for each derivation δ of R, R is δ-weakly rigid and δ-left APP (resp. p.q.-Baer). Finally we prove that R[x;δ] is left APP (resp. p.q.-Baer) if and only if R is δ-left APP (resp. p.q.-Baer).     

A method for simultaneously improving the flame retardancy and toughness of PLA

In order to modify the brittleness and flame retardant properties of poly(lactic acid) (PLA), a series of flame retardant toughened PLA composites were prepared using poly(ethylene glycol) 6000 (PEG6000) as a toughening and charring agent together with ammonium polyphosphate (APP) as an acid source and blowing agent. The fire and thermal behavior of PLA/PEG/APP composites was evaluated by limiting oxygen index (LOI), UL‐94, cone calorimeter, and thermogravimetric analysis (TGA). The results showed that the PLA/PEG/APP system had good charring ability and could improve the flame retardancy of PLA. When the content of APP in the composites was more than 5 wt%, all samples could reach UL‐94 V‐0 rating. The results of mechanical property tests demonstrated that the brittleness of PLA was also improved after blended with PEG6000. All the PLA/PEG/APP composites with an APP content of less than 10 wt% showed an obvious neck and fracture behavior, that is, the tensile behavior of PLA was changed from brittle to ductile. Copyright © 2010 John Wiley & Sons, Ltd.     

基于STM32大气动态雾霾检测系统的设计

大气的质量直接关系到人们的生存环境,衡量大气污染的程度和对身体健康造成的伤害,都离不开对大气的检测。如何进行检测,用什么方法来评判,本文提出一种方法来实时检测大气雾霾的状况,尤其是PM2.5(空气动力学当量直径小于等于2.5微米的颗粒物)被认为是造成雾霾天气的“元凶。大气雾霾监测系统利用雾霾检测器和GPRS传导,将所在地雾霾情况实时监测传输给手机APP终端,手机接收之后将数据整合显示给使用者,达到雾霾监测和提前应对恶劣天气的作用。