The Investigation of Interaction Competition Between ATP and DIPP-Ala,Boc-Ala,or Ala by ESI-MS/MS and Theoretical Calculation

The interactions between ATP and N-(O,O-diisopropyl) phosphoryl-L-alanine (DIPP-Ala), N-(tert-butoxycarbonyl)-L-alanine (Boc-Ala), or L-alanine (Ala) were investigated by electrospray ionization tandem mass spectrometry (ESI-MS/MS). The non-covalent complexes between ATP and Boc-Ala or DIPP-Ala were observed, while the complex between ATP and Ala was not found in the mass spectra. The affinity of DIPP-Ala for ATP was confirmed to be stronger than that of Boc-Ala by competition experiment. Through molecular modeling calculations, it was found that the non-covalent complexes were stabilized by intermolecular hydrogen bonds, and the affinity sequence for ATP was DIPP-Ala > Boc-Ala > Ala by comparing their binding energy, ?35.407 kcal/mol, ?15.634 kcal/mol, ?6.555 kcal/mol, respectively. The results implied that a phosphoryl group was a very important functional group to provide an interaction site between amino acids and ATP, and that N-phosphoryl amino acids can be used as a good model of protein in the studies of molecular recognition of ATP.     

Hydrolysis kinetics of silane coupling agents studied by near-infrared spectroscopy plus partial least squares model

Abstract

A method of Fourier transform near-infrared (FT-NIR) spectroscopy combined with partial least squares (PLS) model was successfully applied to investigate the hydrolysis kinetics of four kinds of silane coupling agents (phenyltriethoxysilane, vinyltriethoxysilane, 3-mercaptopropyltriethoxysilane, 3-chloropropyltriethoxysilane) in an acid-catalyzed EtOH system. The fast scanning speed and high sensitivity of the FT-NIR spectroscopy, and the powerful data processing ability of the PLS, enabled the method to quantitatively and accurately catch the fast changing H₂O concentration during the hydrolysis processes without delay, realizing the study of the fast-paced hydrolysis reactions of the silane coupling agents. The results showed that electrophilic substitution occurred in the hydrolysis reactions, which followed second-order reactions and greatly depend on the catalyst concentration and reaction temperature. The hydrolysis rate constants, activation energy, and Arrhenius Frequency factors were gained. In conclusion, the FT-NIR PLS model is a powerful tool for hydrolysis kinetics researching of the silane coupling agents.     

2-(N2-O,O-dialkylthiodhosphoryl)-hydfazinobenzothi-azole

Abstract

2-(N₂-O,O-Dialkylthiophosphoryl)hydrazinobenzothiazole (I) could be synthesized with satisfactory yields from the reaction of 2-hydrazinobenzothiazole with thiophosphoryl chlorides. At higher temperature bis(dialkoxy)thiophosphoryl derivatives (11) were given.     

Fire properties of silylated α‐zirconium phosphate composites based on polystyrene

α‐zirconium phosphate (ZrP) (prepared by both reflux and hydrothermal methods) is silylated with chlorotrimethylsilane and characterized by X‐ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. Polystyrene/silylated‐ZrP composites show higher thermal stability as the ZrP content increases. Cone calorimetry suggests that the reduction of the peak heat release rate of polystyrene (PS)/ZrP composites does not increase as the ZrP loading increases; the aspect ratio of ZrP has little effect in fire performance of PS/ZrP composites. Copyright © 2013 John Wiley & Sons, Ltd.     

Dissociation of Multisubunit Protein–Ligand Complexes in the Gas Phase. Evidence for Ligand Migration

The results of collision-induced dissociation (CID) experiments performed on gaseous protonated and deprotonated ions of complexes of cholera toxin B subunit homopentamer (CTB₅) with the pentasaccharide (β-D-Galp-(1→3)-β-D-GalpNAc-(1→4)[α-D-Neu5Ac-(2→3)]-β-D-Galp-(1→4)-β-D-Glcp (GM1)) and corresponding glycosphingolipid (β-D-Galp-(1→3)-β-D-GalpNAc-(1→4)[α-D-Neu5Ac-(2→3)]-β-D-Galp-(1→4)-β-D-Glcp-Cer (GM1-Cer)) ligands, and the homotetramer streptavidin (S₄) with biotin (B) and 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-(biotinyl) (Btl), are reported. The protonated (CTB₅ + 5GM1)ⁿ⁺ ions dissociated predominantly by the loss of a single subunit, with the concomitant migration of ligand to another subunit. The simultaneous loss of ligand and subunit was observed as a minor pathway. In contrast, the deprotonated (CTB₅ + 5GM1)^n- ions dissociated preferentially by the loss of deprotonated ligand; the loss of ligand-bound and ligand-free subunit were minor pathways. The presence of ceramide (Cer) promoted ligand migration and the loss of subunit. The main dissociation pathway for the protonated and deprotonated (S₄ + 4B)^n+/– ions, as well as for deprotonated (S₄ + 4Btl)^n– ions, was loss of the ligand. However, subunit loss from the (S₄ + 4B)ⁿ⁺ ions was observed as a minor pathway. The (S₄ + 4Btl)ⁿ⁺ ions dissociated predominantly by the loss of free and ligand-bound subunit. The charge state of the complex and the collision energy were found to have little effect on the relative contribution of the different dissociation channels. Thermally-driven ligand migration between subunits was captured in the results of molecular dynamics simulations performed on protonated (CTB₅ + 5GM1)¹⁵⁺ ions (with a range of charge configurations) at 800 K. Notably, the migration pathway was found to be highly dependent on the charge configuration of the ion. The main conclusion of this study is that the dissociation pathways of multisubunit protein–ligand complexes in the gas phase depend, not only on the native topology of the complex, but also on structural changes that occur upon collisional activation.

Preparation and Antibacterial Function of Quaternary Ammonium Salts Grafted Cellulose Fiber Initiated by Fe2 +-H2O2 Redox

The surface contact disinfecting technique is a newly developed method for water sterilization. In this paper, the grafted quaternary ammonium salts (QAS) antibacterial fibers were prepared and designed to apply for the surface contact disinfecting process in water treatment. The antibacterial fibers were directly prepared by grafting methacryloxylethyl benzyl dimethyl ammonium chloride (DMAE-BC) onto cellulose fiber using thiocarbonate-H₂O₂ redox system. All kinds of factors in the grafting reactions, such as reaction time, reaction temperature, monomer concentration, initiator concentration, which influence the percentage of grafting, were studied and optimized. The modified cellulose fibers were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope(SEM). The effects of the percentage of grafting of the grafted cellulose fibers on bactericidal activity were also studied. The spread plate method was used to characterize the bactericidal activity. The disinfection process was further investigated by directly observing the morphology of the bacterial cells adsorbed on the antibacterial fibers with SEM and measuring extracelluar total protein concentration in suspension. The poly(DMAE-BC)-grafted cellulose ?ber was found to exhibit particularly high activity against E.coli.     

Demulsification of Solids‐Stabilized Emulsions Under Microwave Radiation

Experimental data are presented to show the influence of solid particles on demulsification. It was found that the solid particles could effectively resist demulsification. Compared with conventional heating, microwave radiation can enhance the demulsification rate by an order of magnitude and increase the demulsification effectiveness. The demulsification effectiveness of the emulsions stabilized by graphite powder can reach 82%–89% in a very short time under microwave radiation, whilst that of the emulsions stabilized by barium sulfate can attain 100% under similar conditions.     

Atom Transfer Radical Polymerization of MMA Initiated by 2‐(4‐chloromethyl‐phenyl)‐benzoxazole and Fluorescent Property of PMMA

Atom transfer radical polymerization (ATRP) of MMA was conducted using 2‐(4‐chloromethyl‐phenyl)‐benzoxazole as initiator, CuCl as catalyst, and PMDETA as ligand. The results show that the polymerization is a first order reaction with respect to monomer concentration. The polymerization displayed living character as evidenced by a liner increase of monomer weight with conversation and a relatively narrow distribution (Mn/Mw range from 1.30 to 1.45). The structure of PMMA was analyzed by ¹H‐NMR and proved the polymerization could be controlled to some degree. The optical property of the initiator was well preserved in the resulting PMMA, and the end‐functionalized PMMA exhibited fluorescent emission at 360 nm whether in DMF solution or in film state.     

Preparation and Characteration of UV-cured EA/MMT Nanocomposites Via In-Situ Polymerization

A long-chain surfactant, enzoylbenzyl-N,N-dimethyl-N-octadecylammonium bromide (BDOB) with a benzophenone group, was synthesized to modify the montmorillonites (MMT) for the preparation of nanocomposites via photo-induced polymerization. The BDOB-modified MMT was characterized by the fourier transform infrared spectrometer (FTIR), thermal gravimetric analyzer (TGA) and X-ray diffraction (XRD), and the results of XRD indicated that the intercalated structures of BDOB-modified MMT was obtained. The conversion of the bisphenol A epoxy diacrylate (EA) was quantified by the FTIR, and the results indicated that conversion increased with an increase in the amount of BDOB-modified MMT. The morphologies of the UV-cured EA/MMT nanocomposites prepared from this organically modified MMT were studied by means of XRD and TEM, and the results showed that all the samples contained an intercalated structure with partial exfoliated structure. The results of TGA and mechanical properties also indicated that the thermal and mechanical properties of UV-cured nanocomposites were significantly enhanced due to the presence of the long chain surfactant organically modified MMT.