Gelation and adhesion behavior of mussel adhesive protein mimetic polymer

An acrylamide‐type copolymer containing catechol, amino, and hydroxyl groups was synthesized as a mimetic of the natural mussel adhesive protein (MAP). The obtained copolymer in a phosphate buffer solution (pH = 8.0) formed a hydrogel within 2 h under air, whereas gelation did not proceed under argon atmosphere. We confirmed that the cross‐linking reaction of the synthesized MAP mimetic copolymer was triggered by aerobic oxidation of catechol moieties to form an adhesive hydrogel. Two aluminum plates were adhered by the gelation of the MAP mimetic copolymer solution under humid air at room temperature. The interfacial region between the two aluminum plates failed at a lap shear strength of 0.46 MPa due to cohesive failure of the hydrogel. The adhesion strength was dominated by mechanical strength of the hydrogel as well as the interface interaction of catechol groups with substrate surface. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Isobaric vapor–liquid equilibria for water + propylene glycol monomethyl ether (PGME), water + propyleneglycol monomethyl ether acetate (PGMEA), and PGME + PGMEA at reduced pressures

Isobaric vapor–liquid equilibria were measured for three binary systems of water + propyleneglycol monomethyl ether (PGME), water + propyleneglycol monomethyl ether acetate (PGMEA), and PGME + PGMEA at 93.3, 53.3, 26.7 kPa. The equipment used was a modified Rogalski-Malanoski equilibrium still and an ebulliometer. The NRTL equation correlated the experimental binary data with good accuracy.     

Enzymatic Cell-Surface Decoration with Proteins using Amphiphilic Lipid-Fused Peptide Substrates

Lipid modification of proteins plays a significant role in the activation of cellular signals such as proliferation. Thus, the demand for lipidated proteins is rising. However, getting a high yield and purity of lipidated proteins has been challenging. We developed a strategy for modifying proteins with a wide variety of synthetic lipids using microbial transglutaminase (MTG), which catalyzes the cross-linking reaction between a specific glutamine (Q) in a protein and lysine (K) in the lipid-fused peptide. The synthesized lipid-G₃S-MRHKGS lipid (lipid: fatty acids, tocopherol, lithocholic acid, cholesterol) was successfully conjugated to a protein fused with LLQG (Q-tagged protein) by an MTG reaction, yielding >90 % conversion of the Q-tagged protein in a lipidated form. The purified lipid–protein conjugates were used for labeling the cell membrane in vitro, resulting in best-anchoring ability of cholesterol modification. Furthermore, in situ cell-surface decoration with the protein was established in a simple manner: subjection of cells to a mixture of cholesterol-fused peptides, Q-tagged proteins and MTG.     

Method and mechanism of vapor phase treatment–total reflection X-ray fluorescence for trace element analysis on silicon wafer surface

Vapor phase treatment (VPT) is a pretreatment with hydrofluoric acid vapor to raise the sensitivity of total reflection X-ray fluorescence spectroscopy (TXRF) for trace metal analysis on silicon wafers. The International Organization for Standardization/Technical Committee 201/Working Group 2 (ISO/TC201/WG2) has been investigating the method to analyze 10⁹ atoms/cm² level of metallic contamination on the silicon wafer surface. Though VPT can enhance the TXRF signal intensity from the metallic contamination, it has turned out that the magnitude of the enhancement varies with the type of methods and the process conditions. In this study, approaches to increase TXRF intensity by VPT are investigated using a fuming chamber in an automated VPD instrument. Higher signal intensity can be obtained when condensation is formed on the sample surface in a humidifying atmosphere and with a decreasing stage temperature. Surface observations with SEM and AFM show that particles with ~ 4 μm in diameter are formed and unexpectedly they are dented from the top surface level.     

Program schedule: Symposium on statistical approaches to macromolecular systems in honor of Robert Simha

Abstract

Atomic force microscopy (AFM) has been applied to observe single-chain polymethylmethacrylate (PMMA) particles that were stored for six months at room temperature after being sprayed from very dilute solutions in good solvents, good/poor mixed solvents, and a theta solvent. Nearly monodisperse PMMA standards of molecular weights ranging from 7.90 × 10⁴ to 1.3 × 10⁶ were used to investigate the effect of molecular weight (MW) on the size of the single-chain PMMA particles. These single-chain particles showed close to spherical shapes. The morphology of single-chain PMMA particles of a given molecular weight has found to be identical in spite of different solvents used for solution spraying. Molecular weight dependence of the particle dimension was also found. The diameters of single-chain PMMA particles after correction of tip-geometry effect were compared with the values estimated from molecular weight and density.     

Macroscopic-wetting anisotropy on the line-patterned surface of fluoroalkylsilane monolayers

Micropatterned fluoroalkylsilane monolayer surfaces with liquidphilic/liquidphobic area (line width 1-20 microm) were prepared with few defects by vacuum ultraviolet (VUV) photolithography. The anisotropic wetting of a macroscopic droplet with a 0.5-5 mm diameter on the micropatterned surfaces was investigated. The strong anisotropy of the contact angle and the sliding angle and droplet distortion for fluoroalkylsilane/silanol patterned surfaces was attributed to the difference in the energy barrier of wetting between parallel and orthogonal lines. The wetting anisotropy decreased with decreases in the liquidphilic area. Fluoroalkylsilane/alkylsilane patterned surfaces with small differences in the surface free energies of the components showed anisotropic wetting only for the low-surface-tension liquids.     

Tunable metallization by assembly of metal nanoparticles in polymer thin films by photo- or electron beam lithography

The technique of patterning of surfaces with metal-rich structures on micro- or nanoscales was developed by assembling metal nanoparticles into a thin film of polymer in a controllable way. Palladium (Pd) nanoparticles were incorporated into a thin film of poly(methyl methacrylate) (PMMA) using palladium (II) bis(acetylacetonato), Pd(acac)(2), as a precursor vaporized in a nitrogen atmosphere. Depending upon its dose, the irradiation of a PMMA film by UV light or an electron beam (EB) enhances its reducing capability against Pd(acac)(2). This dependency on dose can be used to control the formation and assembly of Pd nanoparticles. Using this technique, binary patterns consisting of metal-rich and metal-poor regions in the polymer film can be created simply by irradiating the surface of the polymer through a binary photomask. Besides the creation of binary patterns, it is also possible to create grayscale patterns where the density of Pd nanoparticles can be tuned to provide shades of gray by the use of light with continuously modulated intensity. Because the electron beam also enhances the reducing power of PMMA against Pd(acac)(2), it is thus possible to obtain highly metallized films with nanoscale pattern features. The PMMA film can be selectively removed by oxygen plasma treatment or by pyrolysis. Thus, highly metallized surfaces with binary or grayscale patterns can be obtained by selective removal of the PMMA films. The metallized regions possess relatively high resistivity against CF(4) plasma compared to the bare silicon surface; therefore, the metallized surface patterns can be transferred onto the underlying silicon substrate by CF(4) plasma treatment. Because of the nanosize effect of metal nanoparticles, the thermal treatment at 900 degrees C, which is significantly lower than the melting temperature of the bulk Pd, yields continuous metallic features by binding the assembled nanoparticles.     

Effect of molecular packing on adsorption and micelle formation of a homologous cationic surfactant mixture of hexadecyltrimethylammonium bromide and dodecyltrimethylammonium bromide

The surface tension of an aqueous solution of a hexadecyltrimethylammonium bromide (HTAB) and dodecyltrimethylammonium bromide (DTAB) mixture was measured as a function of the total molality and the composition of DTAB at 298.15 K under atmospheric pressure. The phase diagrams of adsorption and micelle formation were constructed and the excess Gibbs energy was evaluated by analyzing the phase diagrams thermodynamically. Both the excess Gibbs energy in the adsorbed film and the excess surface area are negative; therefore the mutual interaction between HTAB and DTAB is said to be stronger than that between the same species and is enhanced with increasing adsorption. By combining the results with those obtained in previous studies, we claimed that DTAB molecules can use effectively the space among the hydrocarbon chains of HTAB molecules and their polar head groups take a staggered arrangement at the surface so as to reduce the electrostatic repulsion. Consequently the dispersion force between hydrophobic chains becomes stronger. Furthermore, the comparison of the excess Gibbs energy in the adsorbed film with that in the micelle shows that the staggered arrangement of molecules is not necessary in the spherical micelle.     

Improvement of stability of a Fe/Mg/Al2O3 catalyst for the decomposition of methane in the presence of O2/CO2

The stability of an Fe/Al₂O₃ catalyst in the methane decomposition in the presence of O₂/CO₂ was found to be improved by the addition of Mg into the catalyst (Mg/Fe=1/1 wt ratio), probably due to suppression of carbon deposition even under CH₄/ O₂/CO₂ (80/10/5 vol. ratio) conditions. This revised version was published online in June 2006 with corrections to the Cover Date.