Postpolymerization modification of a hydroxy monolith precursor. Part I. Epoxy alkane and octadecyl isocyanate modified poly (hydroxyethyl methacrylate‐co‐pentaerythritol triacrylate) monolithic capillary columns for reversed‐phase capillary electrochromatography

A novel precursor monolithic capillary column referred to as “hydroxy monolith” or OHM was prepared by the in situ copolymerization of hydroxyethylmethacrylate (HEMA) with pentaerythritol triacrylate (PETA) yielding the neutral poly(HEMA‐co‐PETA) monolith. The neutral precursor OHM capillary thus obtained was subjected to postpolymerization modifications of the hydroxyl functional groups present on its surface with 1,2‐epoxyalkanes catalyzed by boron trifluoride (BF₃) ultimately providing Epoxy OHM C‐m capillary column at varying alkyl chain lengths where m = 8, 12, 14, and 16 for RP‐CEC. Also, the same precursor OHM was grafted with octadecyl isocyanate yielding Isocyanato OHM C‐18 column to provide an insight into the effect of the nature of the linkage to the surface hydroxyl groups of the OHM precursor. While the epoxide reaction leaves on the surface of the OHM precursor hydroxy‐ether linkages, the isocyanato reaction leaves carbamate linkages on the same surface of the OHM precursor. This study revealed that changing the alkyl chain length resulted in changing the column phase ratio (?) and also the solute distribution constant (K). While increasing the surface alkyl chain length increased steeply the solute hydrophobic selectivity, i.e. methylene group selectivity, the nature of the ligand linkage produced different retention for the same solutes and affected the selectivity of slightly polar solutes. The various monoliths proved very useful for RP‐CEC of different small solutes at varying polarity over a wide range of mobile phase composition.     

Postpolymerization modification of reactive polymers derived from vinylcyclopropane. III. Polymer sequential functionalization using a combination of amines with alkoxyamines,hydrazides, isocyanates,or acyl halides

A new 1,1‐disubstituted‐2‐vinylcyclopropane monomer bearing a ketone and a pentafluorophenyl ester was synthesized and successfully polymerized to yield a polymer with two side chain moieties readily available for post‐polymerization modification. After a quantitative modification of the pentafluorophenyl moiety with amines, a subsequent second functionalization reaction was successfully performed on the ketone moiety leading to a double side‐chain functionalized polymer using two different routes. The first route utilized hydrazide and hydroxylamine derivatives leading to a ketone conversion of 25 to 85%. In the second route, the ketone moiety was first reduced to alcohol (reduction conversion up to 100%) and then converted into the corresponding ester or urethane using acyl halides or isocyanates, respectively, with a conversion ratio of up to 90%. A library of functionalized polymers was synthesized to confirm the effectiveness of this approach. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2841–2849     

Cadmium,lead, copper and manganese determination in human deciduous teeth by electrothermal atomic absorption spectrometry using a lanthanum,palladium and citric acid mixture as chemical modifier

Cadmium, lead, copper and manganese were determined in human deciduous teeth and bone ash 1400 standard reference material by electrothermal atomic absorption spectrometry (ETAAS), using a lanthanum + palladium + citric acid (CA) modifier mixture. Optimum masses and mass ratios of La, La + Pd and La + Pd + CA modifiers for analytes in bone ash 1400 sample solution were investigated. Pyrolysis and atomization temperatures of analytes in a tooth sample solution were obtained with and without modifiers. The mixture of La + Pd + CA was found to be preferable for the determination of analytes in tooth samples and bone ash 1400, dissolved in a mixture of HNO₃ + H₂O₂. The detection limits and characteristic masses of analytes were obtained with or without modifiers based on integrated absorbance for tooth sample solution (2% m/v). The detection limits obtained with La + Pd + CA are 6,24,16 and 46 ng g^?1 for Cd, Cu, Mn and Pb, respectively. Recovery tests for analytes in bone ash 1400 and a tooth solution with La and La + Pd + CA modifier mixture were studied and compared with certified and non certified values. The La + Pd + CA mixture was also applied to the determination of Cd, Pb, Cu and Mn in tooth samples.     

Assembly of poly(dopamine)/poly(acrylamide) mixed coatings by a single‐step surface modification strategy and its application to the separation of proteins using capillary electrophoresis

In this work, a facile approach was developed to modify a fused‐silica capillary inner surface based on poly(dopamine) and poly(acrylamide) mixed coatings for protein separation by capillary electrophoresis. The surface morphology, thickness, and chemical components of poly(dopamine)/poly(acrylamide) mixed coatings on glass slides and silicon wafers were studied by atom force microscopy, ellipsometry, and X‐ray photoelectron spectroscopy, respectively. The hydrophilicity and stability of the mixed coatings on glass slides were investigated by static water contact angle measurements. A comparative study of electroosmotic flow showed that the poly(dopamine)/poly(acrylamide) mixed coatings could provide effective suppression of electroosmotic flow. Meanwhile, the fast and efficient separations of the mixture of four alkaline proteins, the mixture of acidic, basic, and neutral proteins and egg white proteins were obtained by capillary electrophoresis. Furthermore, the consecutive protein separation runs and low RSDs of migration time demonstrated that these poly(dopamine)/poly(acrylamide) mixed coatings were capable of minimizing protein adsorption during the protein separation by using capillary electrophoresis.     

Selection of phage antibodies with GPX activity by combination of phage displayed antibody library with chemical modification and their characterization using a surface plasmon resonance biosensor

Glutathione peroxidase (GPX) is an important antioxidant enzyme, which plays an important role in scavenging reactive oxygen species. To obtain humanized GPX catalytic antibodies, the phage displayed human antibody library on the surface of the filamentous bacteriophage was used to select novel antibodies by repetitive screening. Phage antibodies B8, H6 and C1 with the GSH-binding site were obtained from the library by enzyme-linked immunosorbent assay (ELISA) analysis with four rounds of selection against three haptens, S-2,4-dinitrophenyl t-butyl ester [GSH-S-DNP-Bu (B)], S-2,4-dinitrophenyl t-hexyl ester [GSH-S-DNP-He (H)] and S-2,4-dinitrophenyl cycle-hexyl ester [GSH-S-DNP-cHe (C)], and characterized using surface plasmon resonance (SPR) biosensor. The gold layer was modified by dithiodiglycolic acid (DDA) and three haptens were easily attached to DDA by self-assembling to form a biosensor membrane. The membrane bounds specifically corresponding antibodies. The kinetic process of the reaction between phage antibodies and their haptens was studied by SPR biosensor. In order to improve selectivity, chemical modification was used to incorporate directly catalytic group selenocysteine (Sec) into selected phage clone B8, H6 and C1 to form Se-B8, Se-H6 and Se-C1, respectively. The GPX activities of Se-B8, Se-H6 and Se-C1 were found to be 3000, 2000 and 700 units/μmol, respectively. Compared with conventional ELISA analysis, the proposed method based on SPR biosensor is much more rapid and simpler.     

Matrix-assisted ionization vacuum for protein detection,fragmentation and PTM analysis on a high resolution linear ion trap-orbitrap platform

Matrix-assisted ionization vacuum (MAIV) is a novel ionization technique that generates multiply charged ions in vacuum without the use of laser ablation or high voltage. MAIV can be achieved in intermediate-vacuum and high-vacuum matrix-assisted laser desorption/ionization (MALDI) sources and electrospray ionization (ESI) sources without instrument modification. Herein, we adapt MAIV onto the MALDI-LTQ-Orbitrap XL platform for biomolecule analysis. As an attractive alternative to MALDI for in solution and in situ analysis of biomolecules, MAIV coupling to high resolution and accurate mass (HRAM) MS instrument has successfully expanded the mass detection range and improved the fragmentation efficiency due to the generation of multiply charged ions. Additionally, the softness of MAIV enables potential application in labile post-translational modification (PTM) analysis. In this study, proteins as large as 18.7 kDa were detected with up to 18 charges; intact peptides with labile PTM were well preserved during the ionization process and characterized MS/MS; peptides and proteins in complex tissue samples were detected and identified both in liquid extracts and in situ. Moreover, we demonstrated that this method facilitates MS/MS analysis with improved fragmentation efficiency compared to MALDI-MS/MS.     

Effects of oxygen plasma treatment on the surface of bisphenol A polycarbonate: a study using SIMS,principal component analysis,ellipsometry, XPS and AFM nanoindentation

The effects of oxygen plasma treatment and the subsequent air exposure on the surface composition and properties of bisphenol A polycarbonate (BPA‐PC) were analysed by X‐ray photoelectron spectroscopy (XPS), ellipsometry, static time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) with principal component analysis (PCA) and nanoindentation using an atomic force microscope (AFM). PCA showed systematic changes in the film chemistry after short treatment times (0.1 s), with the main sites of attack being the carbonate and aromatic ring structure. On the basis of this multitechnique analysis, it was unambiguously determined that extended oxygen plasma treatment times resulted in the formation of low‐molecular‐weight material (LMWM) within the first 50 nm on the surface, and not in a cross‐linked skin as has been proposed by other researchers. The study shows that controlled surface modification of BPA‐PC polymers is possible, allowing surface oxygen incorporation without degradation of the polymer structure. This result is relevant for improved adhesion of coatings applied to BPA‐PC polymers. Copyright © 2006 John Wiley & Sons, Ltd.     

Improvement of pore geometry and performances of poly(ethylene terephthalate) track membranes by a protective layer method using plasma-induced graft polymerization of 1H,1H,2H-perfluoro-1-octene monomer

The process of geometrical modification of pores in poly(ethylene terephthalate) track-etched membranes (TM) by use of plasma deposition of a fluorine-containing polymer protective layer on one membrane surface and alkali etching of the other surface has been studied in order to produce membranes with improved performance characteristics. Samples of membranes with conical pores have been obtained which have better filtration efficiency compared with initial TM with cylindric pores. Plasma polymerization of 1H,1H,2H-perfluoro-1-octene at the membrane surface was used to produce the protective layer resistant to alkali solutions. The occurrence of plasma modification and changing of pore geometry have been verified by X-ray photoelectron spectroscopy and scanning electron microscopy studies. The filtration efficiency and selectivity of the modified membranes have been studied.