Preparation and characterization of a novel water soluble amino chitosan (amino-CS) derivative for facilitated transport of CO<Subscript>2</Subscript>

With the goal of obtaining a water soluble polymeric carrier for preparation of fixed facilitated transport membranes, a water soluble amino containing chitosan derivative was prepared through Michael-addition reaction between chitosan and ethyl acrylate followed by amidation of the ester groups with an appropriate diamine. This derivative was characterized using ¹H-NMR spectroscopy. Then, facilitated transport membranes were prepared by casting a thin layer of chitosan derivative/poly(vinyl alcohol) blend on a porous polysolfune support; and the effect of fixed carrier’s content, feed temperature and feed pressure on the CO₂ permeance, and CO₂/CH₄ selectivity of produced membranes were studied. A facilitated transport mechanism for CO₂ through this membrane was concluded.     

TOF MS Investigation of Nickel Oxide CVD

NiO layers were deposited by metal-organic chemical vapor deposition using bis-(ethylcyclopentadienyl) nickel (EtCp)₂Ni and oxygen or ozone. As a continuation of kinetic study of NiO MOCVD the gas-phase, transformations of (EtCp)₂Ni were studied in the temperature range of 380–830 K. Time of reactions corresponding to the residence time of the gas stream in hot zone of the reactor was about 0.1 s under conditions studied. The interaction of (EtCp)₂Ni with oxygen started at 450 K and its conversion rate reached the maximum at 700 K. The interaction of (EtCp)₂Ni with ozone started at 400 K and its conversion rate reached the maximum at 600 K. Transformations of the gas phase with the temperature in the reaction zone were studied, the model reaction schemes illustrating (EtCp)₂Ni transformations in the reaction systems containing oxygen and ozone have developed. In the reaction system (EtCp)₂Ni–O₂–Ar the main gas-phase products at 380–500 K were CO, CO₂, HCO, C₂H₅OH, CpCOOH, and CpO. Formation of the C₂H₂O, C₃H₄O, and C₅H₈O was found at 630–830 K. The same gas-phase species, (C₄H₃O)₂Ni and dialdehydes was formed in the reaction system (EtCp)₂Ni–O₃–O₂–Ar.

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Dual-Polarity Ion Trap Mass Spectrometry: Dynamic Monitoring and Controlling Gas-phase Ion–Ion Reactions

A dual-polarity linear ion trap (LIT) mass spectrometer was developed in this study, and the method for simultaneously controlling and detecting cations and anions was proposed and realized in the LIT. With the application of an additional dipolar DC field on the ejection electrodes of an LIT, dual-polarity mass spectra could be obtained, which include both the mass-to-charge (m/z) ratio and charge polarity information of an ion. Compared with conventional method, the ion ejection and detection efficiency could also be improved by about one-fold. Furthermore, ion–ion reactions within the LIT could be dynamically controlled and monitored by manipulating the distributions of ions with opposite charge polarities. This method was then used to control and study the reaction kinetics of ion–ion reactions, including electron transfer dissociation (ETD) and charge inversion reactions. A dual-polarity collision-induced dissociation (CID) experiment was proposed and performed to enhance the sequence coverage of a peptide ion. Ion trajectory simulations were also carried out for concept validation and system optimization.

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Structural Characterization of a Thrombin-Aptamer Complex by High Resolution Native Top-Down Mass Spectrometry

Native mass spectrometry (MS) with electrospray ionization (ESI) has evolved as an invaluable tool for the characterization of intact native proteins and non-covalently bound protein complexes. Here we report the structural characterization by high resolution native top-down MS of human thrombin and its complex with the Bock thrombin binding aptamer (TBA), a 15-nucleotide DNA with high specificity and affinity for thrombin. Accurate mass measurements revealed that the predominant form of native human α-thrombin contains a glycosylation mass of 2205 Da, corresponding to a sialylated symmetric biantennary oligosaccharide structure without fucosylation. Native MS showed that thrombin and TBA predominantly form a 1:1 complex under near physiological conditions (pH 6.8, 200 mM NH₄OAc), but the binding stoichiometry is influenced by the solution ionic strength. In 20 mM ammonium acetate solution, up to two TBAs were bound to thrombin, whereas increasing the solution ionic strength destabilized the thrombin–TBA complex and 1 M NH₄OAc nearly completely dissociated the complex. This observation is consistent with the mediation of thrombin-aptamer binding through electrostatic interactions and it is further consistent with the human thrombin structure that contains two anion binding sites on the surface. Electron capture dissociation (ECD) top-down MS of the thrombin–TBA complex performed with a high resolution 15 Tesla Fourier transform ion cyclotron resonance (FTICR) mass spectrometer showed the primary binding site to be at exosite I located near the N-terminal sequence of the heavy chain, consistent with crystallographic data. High resolution native top-down MS is complementary to traditional structural biology methods for structurally characterizing native proteins and protein–DNA complexes.

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Determination of trace amounts of nystatin in water and vaccine samples using sodium dodecyl sulfate-coated iron oxide magnetic nanoparticles followed by high-performance liquid chromatography–ultraviolet detection

In this work, magnetic solid-phase extraction based on sodium dodecyl sulfate-coated Fe₃O₄ nanoparticles has been successfully applied for extraction and preconcentration of trace amounts of nystatin from water and vaccine samples prior to high-performance liquid chromatography–ultraviolet detection. Various experimental parameters affecting extraction and recovery of the analyte, such as the amount of sodium dodecyl sulfate, pH of the sample solution, salt concentration, extraction time, sample volume and desorption conditions, were systematically studied and optimized. Under optimized conditions, nystatin was quantitatively extracted. Proper linear range with good coefficient of determination, (R ² > 0.99) and limit of detection and quantification (based on signal-to-noise ratios of 3 and 10) of 2.0 and 5.0 µg L^?1, over the investigated concentration range (5–700 µg L^?1), were obtained, respectively. The intra-day and inter-day relative standard deviations at 50 µg L^?1 level of NYS were 1.4 and 4.5% based on six replicate determinations. The accuracy of the method was evaluated by recovery measurements on spiked samples. Suitable recoveries of 96–102 and 26–44% were achieved (at spiked levels of 50, 300 and 500 µg L^?1) for water and vaccine samples, respectively.     

Boron nitride nanotube (BNNT) as a sensor of hydroperoxyl radical (HO<Subscript>2</Subscript>): A DFT study

In this present study, the adsorption behavior of HO₂ radical on the exterior surface of (5, 0) zigzag boron nitride nanotube (BNNT) has been investigated. The electronic structures and geometries of studied complexes were calculated at B3LYP-D3/6-31++G (d, p) computational level. The value of adsorption energy for the most stable configuration (A) is obtained ?0.68 eV, indicating physisorption process. Meaningful change of HOMO–LUMO gap after adsorption confirming BNNT can be introduced as a promising sensor for sensing of HO₂ radical.     

Applying Direct Yellow 11 to a modified Simons’ staining assay

For quantification of overall fiber accessibility of lignocellulosic substrates, Direct Yellow 11 (C.I. 40000) is a suitable alternative to the discontinued Pylam Products’ dye Direct Orange 15 (C.I. 40002/40003). In this study we present a side-by-side comparison between the two azo-stilbene dyes. We characterize individual dye fractions and provide equations to determine individual concentrations. We present a modified Simons’ staining protocol incorporating the high molecular weight fraction of Direct Yellow 11. We perform tests on lignin, cellulosic, and lignocellulosic materials. In all tests, the two dyes perform similarly and satisfy many accessibility measurement criteria. We demonstrate that the adsorption of Direct Yellow 11 onto a substrate correlates with that substrate’s propensity for enzymatic hydrolysis. We confirm this correlation on a series of organic solvent pretreatments and on a series of lignocellulosic substrates. Finally, we outline the inherent limitations of performing adsorption experiments with Direct Yellow 11 and other high molecular weight dyes.     

Synthesis and properties of novel stilbene-twelve alkyl quaternary ammonium salts as antibacterial optical whitening agents

Four novel stilbene-twelve alkyl quaternary ammonium salts 5a–d were synthesized. All synthesized compounds were characterized by FT-IR, ¹H-NMR and elemental analysis. Compounds 5a–d showed efficient whitening effect on cotton fiber and high fastness. Furthermore, compound 5c showed better stability to light than C186 in aqueous solution. The preliminary biological experiment demonstrated compounds 5a–d possessed significant antibacterial activities. Among them, compound 5d turned out to be the most active compound against Candida albicans with MIC₅₀ 4 μg/mL as well as E. coli with MIC₅₀ 16 μg/mL.     

Measurement of the flexibility of wet cellulose fibres using atomic force microscopy

Flexibility and modulus of elasticity data for two types of wet cellulose fibres using a direct force–displacement method by means of AFM are reported for never dried wet fibres immersed in water. The flexibilities for the bleached softwood kraft pulp (BSW) fibres are in the range of 4–38 × 10¹² N^?1 m^?2 while the flexibilities for the thermomechanical pulp (TMP) fibres are about one order of magnitude lower. For BSW the modulus of elasticity ranges from 1 to 12 MPa and for TMP between 15–190 MPa. These data are lower than most other available pulp fibre data and comparable to a soft rubber band. Reasons for the difference can be that our measurements with a direct method were performed using never dried fibres immersed in water while other groups have employed indirect methods using pulp with different treatments.     

Modification of the Extended UNIQUAC Model to Study the Phase Behavior of the [Bmim]Cl–K<Subscript>2</Subscript>HPO<Subscript>4</Subscript> Aqueous Two Phase System at 298.15 K

Aqueous two phase systems (ATPS), consisting of two incompatible aqueous solutions, are widely used in biological extraction. In recent years, many experimental studies on the phase behavior of ionic liquid(IL)–inorganic salt ATPS systems have been reported but few investigations of the thermodynamics of the IL-based ATPS have been reported. In this work, the Extended UNIQUAC model is modified to calculate the equilibrium of [Bmim]Cl–K₂HPO₄–H₂O ATPS at 298.15 K. All the interaction parameters of the model are salt specific. The results show that the experimental compositions of tie lines are correlated successfully using the proposed model. The root mean square deviation of the mass fraction is 0.0256.