利用MicroBCA和QCM对钛薄膜表面固定纤连蛋白的量化研究与对比

采用物理化学稳定性较好的石英玻璃为基底,用非平衡磁控溅射技术于其表面沉积生物相容性良好的钛薄膜,然后在钛薄膜表面共价固定纤连蛋白。采用傅立叶红外光谱(FT-IR)和X射线光电子能谱(XPS)对各步处理后的材料表面特征进行检测和分析。主要研究了用MicroBCA检测法对样品表面固定的纤连蛋白的定量表征的可行性,并将该结果与用石英晶体微天平(QCM)方法检测获得的纤连蛋白量做了对比和深入分析。结果显示,纤连蛋白可以成功固定到钛薄膜表面,MicroBCA检测法和QCM法的检测结果具有一致性,样品表面纤连蛋白的固定量大约在767～789ng/cm2。     

Characterization of the substructure and properties of immobilized peptides on silicon surface

Immobilization of biomaterials onto solid supports is a means of functionalizing materials for applications such as biosensing. Biologically active peptide (A-A-A-A-G-G-G-E-R-G-D)¹ films were attached to N-hydroxy succinimide ester terminated self-assembled monolayers (SAM) which were covalently linked to a smooth silicon surface via Si–C bonds. The peptide films were characterized using electrical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. The film structures were determined from examination of the capacitance and conductance dispersions with frequency. Analysis of XPS, EIS and FTIR after immobilization of the peptide film at pH 4 and 7 provided information on the extent of the activation and overall coupling efficiencies of the peptides to the N-hydroxy succinimide ester surface. The resulting film structure was markedly altered by attachment of the peptide at pH 4.     

用MicroBCA方法定量检测硅烷化表面固定的纤维连接蛋白

使用microBCA方法（micro-bicinchoninicacid protein assay）,定量研究了人纤维连接蛋白（fi-bronectin,Fn）在硅烷化石英玻璃表面实现共价固定的情况。首先对石英玻璃进行化学清洗,使表面的羟基得以充分暴露。再利用硅烷偶联剂（APTE）将氨基基团引入,并通过EDC/NHS催化体系把人纤维连接蛋白以酰胺键的形式共价固定于该表面。最后用Mi-croBCA方法对该表面固定化的生物分子（Fn）进行量化表征。应用水接触角、X射线光电子能谱（X-rayphotoelectron spectroscopy,XPS）、原子力显微镜（atomic force microscope,AFM）等方法对各步处理效果进行跟踪分析。结果表明Fn在硅烷化石英玻璃表面实现了固定,一定范围内,硅烷化表面的Fn固定量随所使用Fn孵化液浓度的增加而增大。为生物材料表面改性与修饰研究中生物大分子的量化表征提供了一种新方法。     

Influence of mechanical surface treatments on fatigue strength of commercial purity titanium

A comparative study of two mechanical surface treatments of shot peening (SP) and cold rolling (CR) on fatigue strength of commercial purity titanium has been conducted. The treated surface was characterized by using transmission electron microscopy (TEM), X-ray diffraction (XRD), and surface roughness measurements. Experimental result shows that SP and CR increased the fatigue strength of commercial purity titanium, and moreover, the following results were obtained: (1) The improvement of fatigue strength is related to the formation of deformation twins in strengthened layer. Before or after fatigue, the samples strengthened by SP or CR not only have twin shape and number change, but also have twin interactions in the SP and twin-grain boundary interactions in the CR. (2) XRD measurement demonstrated that SP leads to surface compressive residual stress are much higher than those after CR. Surface compressive residual stress has higher relaxation in the SP than in the CR condition during cyclic loading, then the surface compressive residual stress has the same values after fatigue deformation. (3) Surface roughness resulting from SP is ten times of CR.     

A comparison of safety belt use between commercial and noncommercial light-vehicle occupants

The purpose of this study was to conduct an observational survey of safety belt use to determine the use rate of commercial versus noncommercial light-vehicle occupants. Observations were conducted on front-outboard vehicle occupants in eligible commercial and noncommercial vehicles in Michigan (i.e.. passenger cars, vans/minivans, sport-utility vehicles, and pickup trucks). Commercial vehicles that did not fit into one of the four vehicle type categories, such as tractor-trailers, buses, or heavy trucks, were not included in the survey. The study found that the restraint use rate for commercial light-vehicle occupants was 55.8% statewide. The statewide safety belt use rate for commercial light-vehicles was significantly lower than the rate of 71.2% for noncommercial light-vehicles. The safety belt use rate for commercial vehicles was also significantly different as a function of region, vehicle type, seating position, age group, and road type. The results provide important preliminary data about safety belt use in commercial versus noncommercial light-vehicles and indicate that further effort is needed to promote safety belt use in the commercial light-vehicle occupant population. The study also suggests that additional research is required in order to develop effective programs that address low safety belt use in the commercial light-vehicle occupant population.     

Evaluation of hydrogen atom density generated on a tungsten mesh surface

The density of hydrogen atoms supplied from hot tungsten (W) wires with a mesh structure to a tungsten phosphate glass plate substrate surface was evaluated. Variations in the hydrogen atom density were measured as a function of the mesh temperature (1000 to 1800 °C) and the exposure time (3 to 60 min). It became apparent that the quantity of H atoms supplied from hot W mesh was one order of magnitude larger than that supplied from hot W wires without a mesh structure, for the same temperature and surface area of the wire.     

Correlation between protein binding strength on immobilized metal affinity chromatography and the histidine-related protein surface structure

Immobilized metal affinity chromatography (IMAC) was investigated for its ability to characterize the histidine-related surface structure of a protein, that is, a histidine residue's surface accessibility and its potential involvement in intramolecular interactions. T4 lysozyme was chosen as the model protein. Seven amino acid sites were selected on the basis of their relative surface accessibility, and they were substituted with histidine via site-directed protein mutagenesis to generate seven T4 lysozyme variants, each containing only one histidine residue on its surface, with various surface accessibility. IMAC was then used to experimentally quantify the interaction of each lysozyme variant with immobilized copper ions. A direct correlation was shown between the protein binding affinity and the surface accessibility of the histidine residue. Of all the lysozyme variants, K83H and K147H showed unusually low binding strength, as compared with variants having a histidine residue with a similar surface accessibility. However, with the aid of molecular modeling, their relatively low binding affinities were predicted to be the result of the involvement of the histidine residue in intramolecular interactions. In contrast to previously reported results, our results showed that lysozyme still binds to the IMAC column, even if its histidine residue is involved in intramolecular bonding, such as a hydrogen bond, albeit at reduced strength, as compared with the variant containing a histidine residue with a similar surface accessibility.     

Sinterability of commercial 8 mol% yttria-stabilized zirconia powders and the effect of sintered density on the ionic conductivity

The sintering behaviour of a number of commercially produced 8 mol% yttria-stabilized zirconia powders has been studied. The effect of different sintering regimes on the density and microstructure of the sintered ceramic was determined using density measurements, scanning electron microscopy (SEM) and dilatometry. The chemical homogeneity, particle size and the morphology of the as-received powder were related to the sintering behaviour of the different commercial powders. Powders prepared via a route which involved a spray-drying step sintered more readily than those prepared without a spray-drying step. Plasma-derived powders did not sinter to as high an apparent density as co-precipitated powders. The effect of sample density on the ionic conductivity of sintered YSZ ceramics was studied using a.c. impedance spectroscopy. This technique allowed separation of the bulk and grain-boundary components, enabling clear intepretation of the effects of sample porosity of the conduction pathways. Ceramics prepared from the three different powders achieved a bulk ionic conductivity of 16 S cm-1 at 1000 °C for sintered densities of 95% or greater. The results obtained are compared to values reported for a variety of other commercial powders. © 1998 Kluwer Academic Publishers     

The effect of process parameters on physical and mechanical properties of commercial low density polyethylene/ORG-MMT nanocomposites

Polyethylene/organo-montmorillonite clay (org-MMT) nanocomposites were prepared utilizing PP-g-MA as a compatibilizer by melt intercalation method. In order to increase the miscibility of polyethylene (PE) with nanoparticle surface at firs, a primary masterbatch consist of compatibilizer and org-MMT was prepared then, this compound was melt intercalated with PE to synthesis the PE/org-MMT nanocomposites. In this study, the presence of commercial low density polyethylene in Nanocomposites structure and also the effect of process parameters such as: amount of nanoparticles, mixing rate and mixing time on nanocomposite structure and properties have been investigated. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) results showed that the interlayer distance of nanoparticle layers increased and a partially intercalated structure was prepared by melt intercalation method. Interaction between polyethylene chains and nanoparticle layers could be improved if the control of above parameters causes to penetrate the chains into nanoclay layers; by an optimization, this effect could improve the physical and mechanical properties. The DSC data revealed that melting temperature has slowly increased and crystalinity has lightly decreased. Consequently we can claim the thermal properties of LDPE/clay nanocomposite did not considerably change with clay content. A rise in the mechanical properties such as yield stress and modulus was observed by tension test; by addition of 5% clay content the tensile strength increased about 7%, the tensile modulus enhanced about 60% and the yield stress increased about 16% in comparison with the pure LDPE.     

Selective extraction and detection of noble metal based on ionic liquid immobilized silica gel surface using ICP-OES

In this study, an efficiently employed ionic liquid combined with commercially available silica gel (SG–ClPrNTf₂) was developed for selective detection of gold(III) by use of inductively coupled plasma–optical emission spectrometry (ICP-OES). The selectivity of SG–ClPrNTf₂ was evaluated towards seven metal ions, including Y(III), Mn(II), Zr(IV), Pb(II), Mg(II), Pd(II) and Au(III). Based on pH study and distribution coefficient values, the SG–ClPrNTf₂ phase was found to be the most selective towards Au(III) at pH 2 as compared to other metal ions. The adsorption isotherm of Au(III) on the SG–ClPrNTf₂ phase followed the Langmuir model with adsorption capacity of 59.48 mg g^?1, which was highly in agreement with experimental data of adsorption isotherm study. The kinetics study indicated that Au(III) adsorption kinetics data were well fit with the pseudo-second-order kinetic model on the basis of correlation coefficient fitting (0.996) and adsorption capacity agreement (62.26 mg g^?1). Furthermore, SG–ClPrNTf₂ phase was effectively performed for the determination of Au(III) in real water samples with satisfactory results.     

Deposition of bone-like hydroxyapatite on the surface of silk cloth with the aid of immobilized urease

Continuous layers of hydroxyapatite were deposited on silk cloth from aqueous solutions by using urease as the precipitant supplier. Silk cloth was surface-modified with urease and was immersed in an aqueous solution containing Ca²⁺, PO₄³⁻, and urea. As urea was hydrolyzed to form ammonia with the aid of the immobilized urease, hydroxyapatite precipitated predominantly on the surface of the silk cloth. It took only a few hours to form continuous layers of hydroxyapatite on the silk cloth. The resultant hydroxyapatite was found to be bone-like apatite because it had low crystallinity, contained carbonate ion in the lattice, and had a calcium-deficient composition.     

A comparison study of the Boussinesq and the variable density models on buoyancy-driven flows

When density variations are sufficiently small the Boussinesq approximation is valid. The approximation is introduced to reduce the degree of the complexity of density variations and implies that density effects are considered only in the buoyancy force term of the momentum equation. Because of its simplicity in practical implementations, the approximation is widely used. Although there are many studies related to the approximation, some important characteristics are still missing. In this article, we compare the Boussinesq approximation and variable density models for the two-dimensional (2D) Rayleigh–Taylor instability with a phase-field method. Numerical experiments indicate that for an initially symmetric perturbation of the interface the symmetry of the heavy and light fronts for the Boussinesq model can be seen for a long time. However, for the variable density model, the symmetry is lost although the flow starts symmetrically.     

Detection of phosphopeptides by localized surface plasma resonance of titania-coated gold nanoparticles immobilized on glass substrates

We herein demonstrate a new sensing method for phosphopeptides by localized surface plasmon resonance (LSPR) using titania-coated gold nanoparticles immobilized on the surface of a glass slide as the sensing substrate and using UV-visible spectrophotometry as the detection tool. Titania has been known to be an effective substrate for binding with phosphorylated species. The detection principle is the shift of wavelength of optical absorption due to SPR of the gold nanoparticles induced by binding of phosphorylated species with titania on the surface of the gold nanoparticles. The feasibility of the approach is demonstrated by detection of tryptic digest products of beta-casein and milk. Gold nanoparticles coated with thin films of titania, immobilized on a glass slide, can selectively bind traces of phosphopeptides from complex samples, resulting in a wavelength shift of the absorption band in the SPR spectrum with good reproducibility. The LSPR results are confirmed by matrix-assisted laser desorption/ionization mass spectrometry. The detection limit for the tryptic digest product of beta-casein is 50 nM.     

The density of the craze layer on the fracture surface of polystyrene

The refractive index and the density of the craze layer on the fracture surface of polystyrene have been measured directly from interferometric measurement of level differences on the fracture surface. The experimental results are in approximate agreement with the values calculated from either the Lorenz-Lorentz equation or Rayleigh's equation for parallel rods.     

The influence of surface roughness and pre-oxidation state on the wettability of aluminium nitride by commercial brazes

The effects of roughness (Ra = 0.17–0.20 m) and of pre-oxidation of the AlN ceramic surface on its wettability and contact interaction with commercial brazing alloys CB4 and CB5 of Ag-Cu-Ti composition have been studied. Wettability has been determined by the sessile drop method at three holding temperatures (810, 900 and 950°C). Particularities of the interface interaction have been identified by microprobe analysis for pre-oxidized samples. Experimental data are compared with data for samples polished to Ra = 0.02–0.03 m not subjected to pre-oxidation. The results show that, for the systems under study, surface roughness does not influence the contact angle value significantly. Pre-oxidation of the AlN in air at 1250°C, however, tends to reduce wettability as a result of the replacement of braze-aluminium nitride interaction by braze-surface aluminium oxide interaction.     

Electron density on the surface of a dielectric interacting with a plasma

The density functional method is used to calculate the electron density on the surface of a dielectric interacting with a gas-discharge plasma.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 48, No. 2, pp. 284–289, February, 1985.