Improvements in monitoring the N-terminal valine adduct in human globin after exposure to sulfur mustard and synthesis of reference chemicals

The N-terminal valine adduct (HETE-Val) in globin is believed to behave as a long-lived biomarker after exposure to sulfur mustard (HD). Development of a highly sensitive method for monitoring HETE-Val, particularly at low HD exposure levels or for retrospective detection, would be a significant achievement. In this study, by improving the sample preparation method, a sensitive NCI-GC/MS method was established for the analysis of HETE-Val in globin after HD exposure. To optimize and investigate the sample preparation method, all the relevant HETE-Val chemicals were synthesized, purified, and characterized. By carrying out optimized solid phase extraction (SPE) cleanup followed by modified Edman degradation results in a low detection level and clean baseline. The minimum detectable exposure level of human blood (in vitro) to HD is 20 nmol/L (S/N > 3). The interday and intraday precisions of the proposed method were found to be acceptable with less than a 15% relative standard deviation (RSD). A nearly linear dose-effect relationship was observed between HETE-Val and a HD exposure concentration range of 0.1-120 μmol/L. The percentage of HD that reacted with N-terminal valine in globin obtained from human blood (in vitro) was quantified using the proposed method.     

High speed injection molding of high density polyethylene �� Effects of injection speed on structure and properties

Thin wall samples of high density polyethylene (HDPE) were prepared via injection molding with different injection speeds ranging from 100 mm/s to 1200 mm/s. A significant decrease in the tensile strength and Young??s modulus was observed with increasing injection speed. In order to investigate the mechanism behind this decrease, the orientation, molecular weight, molecular weight distribution, melt flow rate, crystallinity and crystal morphology of HDPE were characterized using two-dimensional wide-angle X-ray diffraction (2D-WAXD), gel permeation chromatography (GPC), capillary rheometry and differential scanning calorimetry (DSC), respectively. It is demonstrated that the orientation, molecular weight, molecular weight distribution, melt flow rate and crystallinity have no obvious change with increasing injection speed. Nevertheless, the content of extended chain crystals or large folded chain crystals was found to decrease with increasing injection speed. Therefore, it is concluded that the decrease in tensile properties is mainly contributed by the reduced content of extended chain crystals or large folded chain crystals. This study provides industry with valuable information for the application of high speed injection molding.     

Co-overexpression of PpPDI Enhances Secretion of Ancrod in Pichia pastoris

Ancrod, a serine protease purified from the venom of Agkistrodon rhodostoma, is highly specific for fibrinogen. It causes anticoagulation by defibrinogenation and has been used as a therapeutic anticoagulant for the treatment of moderate to severe forms of peripheral arterial circulatory disorders in a variety of countries. The DNA of ancrod was amplified by recursive PCR with a yeast bias codon and cloned into the pGEM-T Easy vector. In order to achieve a high level secretion and a full activity expression of ancrod in Pichia pastoris (P. pastoris), the P. pastoris protein disulfide bond isomerase (PpPDI) was co-overexpressed in the strain. The secretion characteristics of ancrod with and without PpPDI were examined. With co-overexpression of PpPDI, the production of recombinant ancrod (rAncrod) was increased to 315 mg/L in the culture medium, which is twofold higher than the control strain carrying only the ancrod gene. Through purified by Ni2? affinity chromatography and phenyl Sepharose column, the purity of rAncrod was found to be as high as 95.2%. The fibrinogenolytic and zymographic activities of the rAncrod were determined and found to be similar to that of the native protein. This improved expression system can facilitate further studies and the industrial production of ancrod.     

Screening and Identification of a Fungal β-Glucosidase and the Enzymatic Synthesis of Gentiooligosaccharide

After screening with 0.1% esculoside and 0.03% FeCl₃, we identified from rotten wood a fungal isolate HML0366 that produces high amount of β-glucosidase. Phenotypic and rDNA internal transcribed spacer sequence analyses indicated that the isolate belongs to Aspergillus oryzae. The β-glucosidase produced by HML0366 had an activity of 128 U/g. high performance liquid chromatography analysis also demonstrated a high transglycosylation activity of the crude enzyme. The β-glucosidase was stable between pH 4–10 at 60 °C. A gentiobiose yield of 30.86 g/L was achieved within 72 h of the enzymatic reaction at pH 5 and 55 °C using 50% glucose as the substrate. For the first time, we report here the isolation of an A. oryzae strain producing β-glucosidase with high hydrolytic activities. The crude enzyme has a high transglycosylation activity, which enables the enzymatic synthesis of gentiooligosaccharides.     

Internal standard tracked dilution to overcome challenges in dried blood spots and robotic sample preparation for liquid chromatography/tandem mass spectrometry assays

Dried blood spot (DBS) technology is an emerging alternative for sample collection in bioanalysis. Dilution for DBS samples is a challenge due to its solid sample format. Currently, DBS samples requiring dilution were first extracted as regular samples and then diluted with extracted blank samples containing internal standard (IS). Since the dilution step is a volume-critical step, extra care has to be taken to achieve accurate dilution when dealing with limited volume extracted samples. Here, we introduce an alternative sample dilution for liquid chromatography/tandem mass spectrometry (LC/MS/MS) assays using IS to track the dilution step. Dilution factor-adjusted IS working solution was first added to the sample requiring dilution before sample processing; subsequently, the processed sample was approximately diluted into the assay linear response range before LC/MS/MS analysis. We define this approach as "IS-tracked dilution". The advantage of this approach is that the diluting step is tracked by the IS and is no longer a volume-critical step. Another recognized challenge related to sample dilution is automatic sample dilution using a liquid handler. This "IS-tracked dilution" may also help address some of the challenges for automatic sample dilution of liquid samples. This new dilution approach was proven to be effective and convenient in both plasma assays and DBS assays using omeprazole as a probe compound.     

Synthesis of heteroarylidene malonate derived bis(thiazolines) and their application in the catalyzed Friedel–Crafts reaction

A series of novel heteroarylidene malonate derived bis(thiazoline) ligands 1 and 2 were synthesized and applied to a Friedel-Crafts reaction between indole and alkylidene malonate. The Cu(OTf)₂ complex of ligand 2b bearing a benzyl group afforded moderate to excellent enantioselectivity for the adducts (up to >99% ee).     

Properties of cellulose films prepared from NaOH/urea/zincate aqueous solution at low temperature

Cellulose films were successfully prepared from NaOH/urea/zincate aqueous solution pre-cooled to −13 °C by coagulating with 5% H₂SO₄. The cellulose solution and regenerated cellulose films were characterized with dynamic rheology, ultraviolet–visible spectroscope, scanning electron microscopy, wide angle X-ray diffraction, Fourier transform infrared (FT-IR) spectrometer, thermogravimetry and tensile testing. The results indicated that at higher temperature (above 65 °C) or lower temperature (below −10 °C) or for longer storage time, gels could form in the cellulose dope. However, the cellulose solution remained a liquid state for a long time at 0–10 °C. Moreover, there was an irreversible gelation in the cellulose solution system. The films with cellulose II exhibited better optical transmittance, high thermal stability and tensile strength than that prepared by NaOH/urea aqueous solution without zincate. Therefore, the addition of zincate in the NaOH/urea aqueous system could enhance the cellulose solubility and improve the structure and properties of the regenerated cellulose films.     

Ru0.7Si0.3O2/Ti电极电催化氧化处理硝基苯废水

制备了Ru0.7Si0.3O2/Ti电极,并以该电极作为氧化阳极,不锈钢为阴极,电催化氧化降解废水中硝基苯。 实验结果表明,当硝基苯初始质量浓度为220 mg/L时,最佳条件为：电流密度25×10-3 A/cm2;Na2SO4作为电解质时加入量为8 g/L;溶液初始pH=2。 在此最佳条件下,硝基苯去除率大于85%,TOC去除率大于50%,表明Ru0.7Si0.3O2/Ti阳极能有效去除废水中有机污染物;对中间产物的检测结果表明,硝基苯的降解是阴阳两极协同作用的结果。     

氟喹诺酮类抗生素与赤藓红的共振瑞利散射光谱研究及其分析应用

在Ph4.0～5.0的BR缓冲介质中,赤藓红(Ery)与莫西沙星(MXFX)和加替沙星(GTF)等氟喹诺酮类抗生素(FLQs)相互作用形成1:1离子缔合物,体系反应导致共振瑞利散射(RRS)显著增强并出现新的RRS光谱.两种药物的反应产物具有相似的光谱特征,最大散射波长位于568nm处,并在342nm和378nm处有2个较小的散射峰.在342nm处一定浓度的抗生素与散射增强成正比,两种氟喹诺酮类药物的线性范围分别是0.02～2.7μg/mL(MXFX)和0.06～10.2μg/mL(GTF).据此建立了测定氟喹诺酮类药物的新方法,已用于胶囊和人尿液中的FLQs测定,并对反应机理和RRS增强的原因作了讨论.