Dephosphorylation of intact glycoprotein to greatly improve digestion efficiency coupled with matrix-assisted laser desorption/ionization–Fourier transform ion cyclotron resonance mass spectrometric analysis

Sialylation is essential for a variety of cellular functions. Herein, we used bovine fetuin with three potential N-linked glycosylation sites containing complex-type glycan structures, four potential O-linked glycosylation sites and six potential phosphorylation sites as a model compound to develop a highly-efficient digestion strategy for sialylated glycoproteins and efficient enrichment strategy for sialylated glycopeptides using titanium dioxide. The former according to the process of alkaline phosphatase digestion followed by tryptic digestion and then proteinase K digestion could greatly improve the enzymatic efficiency on fetuin, and the latter could obviously enhance the enrichment efficiency for multisialylated glycopeptides using phosphoric acid solution as elution buffer. The mass spectra of the enriched glycopeptides derived from fetuin reveal that several series of the ion clusters with mass difference of 291 Da correspond to the presence of multisialylated glycopeptides. In addition, the approach was applied to characterize the sialylated status of α2-macroglobulin and transferrin, respectively, from the sera of healthy subjects and sex- and age-matched patients with thyroid cancer, and their spectra indicate that the change in the amount of the glycoforms containing different number of sialic acid (SA) residues from one glycosylation site may be used to differentiate between healthy subjects and cancer cases.     

Resonant-Mie-scattering of aggregates of phosphomolybdate and papaverine for measuring activities and screening inhibitors of cyclic nucleotide phosphodiesterase isozymes

A resonant-light-scattering (RLS) method was proposed to quantify phosphate for screening inhibitors of isozymes of cyclic nucleotide phosphodiesterase (PDE). In acidified mixtures of phosphate, papaverine and molybdate, there were aggregates exhibiting micrometre sizes, no absorbance peaks over 360 nm but strong RLS peaks at 392 nm; Mie scattering thus accounted for the RLS signals. When papaverine was added before molybdate to acidified samples of phosphate, RLS signals at 392 nm were stable from 5 to 25 min since the addition of molybdate; after optimization, phosphate from 0.40 to 3.60 μM was quantifiable. This RLS method tolerated 60 mg L⁻¹ proteins besides common PDE inhibitors and dimethyl sulfoxide in acidified samples of phosphate; the integration of this RLS method with the coupled action of a phosphomonoesterase on PDE product was thus rational to measure PDE activities without the removal of proteins in samples. By quantifying activities of a truncated mutant of human PDE4B2 via this RLS method, Michaelis–Menten constant, inhibition constants of rolipram, papaverine and theophylline varied over three magnitudes and were consistent with those estimated by an improved malachite green assay of phosphate, respectively. Hence, this novel RLS method was promising for screening inhibitors of PDE isozymes.     

Regular arrays of triangular‐microstructure formed on silicon (111) surface via ultrafast laser irradiation in KOH solution

The regular micrometer‐scale triangular arrays were formed using ultrafast femtosecond laser irradiation on (111) surface of silicon wafer immersed in KOH solution (0.1 g/ml). At low laser fluence, the resulting surface is covered by triangular pits microstructures, whereas at high laser fluence, the structures are transformed to multilayer‐triangular stacks‐microstructures. The number of triangular stacks layer increased as the laser fluence increased. The formation of triangle microstructure arrays depends on both silicon surface crystallographic orientation and the concentration of KOH solution. Either for lower KOH solution concentration (0.02 g/ml) or other silicon crystallographic orientation, triangle arrays cannot be obtained. We attribute the formation of triangular microstructure arrays to the laser‐assisted chemical etching process. Copyright © 2013 John Wiley & Sons, Ltd.     

Micellar Effects on Alkaline Hydrolysis of 3,5-Dinitro-2-chloro Benzotriflouride and 2,4-Dinitrochloro Benzene in Aqueous-Acetonitrile Mixtures

Reaction rate for alkaline hydrolysis of the substrates 3,5-dinitro-2-chloro benzotriflouride (DNCBTF) (1) at 30°C and 2,4-dinitrochloro benzene (DNCB) (2) at 50°C separetely with NaOH as nucleophile is carried out spectrophotometrically in mixed aqueous-acetonitrile solvents. In each system, cationic surfactant as dodecyltrimethyl ammonium bromide (DoTAB), or anionic one as sodium dodecyle sulfate (SDS) is used in wide range of concentrations to study the effect of micelle on the reaction rate. The micellar effect is explained in term of modified pseudo phase ion exchange model. Pseudo first order rate constant, k_obs is obtained for each of the nucleophile and for both substrates 1 and 2 at all range of X_AN · k_obs at given [OH^?] and in presence of any substrate is found to increase with the increase of DoTAB,while decrease with the increase of SDS as micellar phases. Critical micelle concentrations (CMCs) in similar trend are observed to increase in DoTAB while decrease in SDS systems by increasing acetonitrile (AN) content. Micellar binding constant (K_S) between any type of given substrate and the formed micelle, is found to decrease in presence of DoTAB and increase in SDS micellar phases by increasing AN content. Finally, the ratios between pseudo first order rate constants for hydrolysis in micellar phase k_M to that in the bulk phase k_w for DoTAB and SDS systems are found to be greater than and smaller than unity respectively at any given X_AN where the data indicated for (1) is always higher than those for (2). The results concluded that micelle DoTAB is working as a catalyst for the reaction rate, while that for SDS is considered as an inhibitor.     

碱液后处理对纳米ZSM-5沸石孔道和酸度的影响

采用XRD、N2物理吸附、NH3-TPD以及TEM、IR和NMR手段,系统研究了NaOH碱液后处理对低硅铝比纳米ZSM-5沸石(Si/Al摩尔比为14.5、晶粒度为20～50 nm)孔道和酸度的影响.结果表明,在碱液中,低硅铝比纳米ZSM-5沸石主要发生限域脱硅,而且低硅铝比纳米ZSM-5沸石的碱液脱硅难度大于高硅铝比沸石.但在适当的碱液处理条件下(碱硅比为0.19～0.35,温度为60～80℃,处理时间为2～5 h)可以在其晶体内产生大量介孔,增加比表面积和孔容;同时增加弱酸和中强酸的浓度,并提高L酸比例.L酸的大量增加主要是由于产生了裸露的骨架铝(≡Alδ+),这与文献的观点有所不同.     

在四氯合锌离子诱导下反式六元瓜环与碱金属离子构筑的配位超分子自组装体

在盐酸介质中,通过四氯合锌离子诱导,碱金属离子能与反式六元瓜环端口羰基氧原子直接配位构筑形成超分子自组装体。单晶结构表明在HCl介质中,四氯合锌离子形成"蜂巢结构",而且在[ZnCl₄]^2-诱导作用下,碱金属离子和反式六元瓜环端口羰基氧直接配位形成一维超分子自组装体而填充在"蜂巢结构"中。     

酸洗脱矿对胜利褐煤热解过程中N迁移转化的影响

在石英管流化床反应器中对胜利褐煤进行快速热解实验,考察了773~1 173 K下酸洗脱矿对胜利褐煤热解过程中N迁移转化规律的影响。通过比较原煤和酸洗后煤中N的不同逸出规律可以得出,影响酸洗前后胜利褐煤热解过程中N迁移转化规律的主要是碱金属Na及碱土金属Ca;热解过程中,煤中的Na和Ca促使煤中的N向NH3转化并有效抑制了HCN的生成,金属离子的存在对催化焦油N转化为NH3的作用较为明显;原煤中的碱金属和碱土金属的赋存使半焦裂解反应加剧,降低了固体半焦的产率,半焦N的产率也随之减少;与原煤相比,酸洗煤热解半焦中的吡啶型N(N-6)含量较多,而吡咯型N(N-5)和季N(N-Q)相对较少。     

The Effect of Alkaline Addition in Hydrothermal Pretreatment of Empty Fruit Bunches on Enzymatic Hydrolysis Efficiencies

In general, lignocellulosic biomass contains three major components, namely lignin, hemicellulose and cellulose which are the polymers of C5 and C6 sugars. Thus, there is potential to utilize of this biomass for bioethanol production. The hydrolysis of cellulose into glucose was difficult due to the more fibrous nature and thus inhibit enzyme penetration into the cellulose. In order to solve this problem, hydrothermal pretreatment can be used for breaking the bonds within the lignin structure and increase the accessibility of enzyme into the cellulose. In this study, the effect of chemical addition, sodium hydroxide (NaOH) and calcium oxide (CaO) in hydrothermal pretreatment at 180 °C and 30 minutes reaction time of palm oil empty fruit bunches (EFB) on the enzymatic hydrolysis efficiencies was investigated. The enzymatic hydrolysis of hydrothermally pretreated EFB give the highest concentration of glucose at 0.67 g/L while the hydrothermally pretreated of EFB in the presence of NaOH gives the lowest glucose concentration 0.45 g/L.     

Galvanostatically Deposited PtNi Thin-Films as Electrocatalysts for the Hydrogen Evolution Reaction

The synthesis of hybrid platinum materials is fundamental to enable alkaline water electrolysis for cost-effective H₂ generation. In this work, we have used a galvanostatic method to co-deposit PtNi films onto polycrystalline gold. The surface concentrations of Ni (Γ_Ni) and Pt (Γ_Pt) were calculated from electrochemical measurements; the Γ_Pt/Γ_Ni ratio and electrocatalytic activity of these materials towards hydrogen evolution reaction (HER) in 1 M KOH show a strong dependence on the current density pulse applied during the electrodeposition. Analysis of the Tafel parameters hints that, on these deposits, HER proceeds through a Volmer-Heyrovsky mechanism. The galvanostatically deposited PtNi layers present a high current output per Pt gram, 3199 A g_Pt⁻¹, which is significantly larger compared to other PtNi-based materials obtained by more extended and more complex synthesis methods.     

Nucleophilic Substitution at Tetracoordinate Phosphorus. Stereochemical Course and Mechanisms of Nucleophilic Displacement Reactions at Phosphorus in Diastereomeric cis- and trans-2-Halogeno-4-methyl-1,3,2-dioxaphosphorinan-2-thiones: Experimental and DFT Studies

Geometrical cis- and trans- isomers of 2-chloro-, 2-bromo- and 2-fluoro-4-methyl-1,3,2-dioxaphosphorinan-2-thiones were obtained in a diastereoselective way by (a) sulfurization of corresponding cyclic P^III-halogenides, (b) reaction of cyclic phosphorothioic acids with phosphorus pentachloride and (c) halogen–halogen exchange at P^IV-halogenide. Their conformation and configuration at the C₄-ring carbon and phosphorus stereocentres were studied by NMR (¹H, ³¹P) methods, X-ray analysis and density functional (DFT) calculations. The stereochemistry of displacement reactions (alkaline hydrolysis, methanolysis, aminolysis) at phosphorus and its mechanism were shown to depend on the nature of halogen. Cyclic cis- and trans-isomers of chlorides and bromides react with nucleophiles (HO⁻, CH₃O⁻, Me₂NH) with inversion of configuration at phosphorus. DFT calculations provided evidence that alkaline hydrolysis of cyclic thiophosphoryl chlorides proceeds according to the S_N2-P mechanism with a single transition state according to the potential energy surface (PES) observed. The alkaline hydrolysis reaction of cis- and trans-fluorides afforded the same mixture of the corresponding cyclic thiophosphoric acids with the thermodynamically more stable major product. Similar DFT calculations revealed that substitution at phosphorus in fluorides proceeds stepwise according to the A–E mechanism with formation of a pentacoordinate intermediate since a PES with two transition states was observed.