青柳 里果

Protein-adsorbed dialysis membranes are evaluated with time-of-flight secondary ion mass spectrometry (TOF-SIMS) chemical imaging technique. Protein adsorption causing permeability change is one of big issues in the development of dialysis membranes. Bovine serum albumin adsorption onto three kinds of dialysis membranes has been evaluated with TOF-SIMS. In the present study three kinds of proteins, bovine serum albumin, alpha-chymotripsinogen A, and cytochrome C adsorbed onto hollow-fiber dialysis membranes, were measured by means of TOF-SIMS and then TOF-SIMS spectra were analyzed using mutual information. Then specific peaks of fragment ions related to alpha-chymotripsinogen A and bovine serum albumin were found, respectively. In this condition, however, specific peaks to cytochrome C were not able to find compared with other samples. Finally, chemical images of alpha-chymotripsinogen A and bovine serum albumin, respectively, adsorbed onto the membranes with coexisting proteins were obtained. The results of TOF-SIMS images of the proteins on the membranes show different tendency of adsorption depending on co-existing proteins. Further study is needed to study more detailed protein adsorption onto the membranes with co-existing proteins. (c) 2006 Elsevier B.V. All rights reserved.

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is capable of chemical imaging of proteins on insulated samples in principal. However, selection of specific peaks related to a particular protein, which are necessary for chemical imaging, out of numerous candidates had been difficult without an appropriate spectrum analysis technique. Therefore multivariate analysis techniques, such as principal component analysis (PCA), and analysis with mutual information defined by information theory, have been applied to interpret SIMS spectra of protein samples. In this study mutual information was applied to select specific peaks related to proteins in order to obtain chemical images. Proteins on insulated materials were measured with TOF-SIMS and then SIMS spectra were analyzed by means of the analysis method based on the comparison using mutual information. Chemical mapping of each protein was obtained using specific peaks related to each protein selected based on values of mutual information. The results of TOF-SIMS images of proteins on the materials provide some useful information on properties of protein adsorption, optimality of immobilization processes and reaction between proteins. Thus chemical images of proteins by TOF-SIMS contribute to understand interactions between material surfaces and proteins and to develop sophisticated biomaterials. (c) 2005 Elsevier B.V. All rights reserved.

The thermal behavior of boron and hydrogen in a SiN-capped p-type MOSFET was investigated in order to explain SiN-enhanced boron diffusion in SiO2. Measured hydrogen profiles indicated that hydrogen in the SiN migrated into the gate oxide during annealing under nitrogen. When this structure was annealed under nitrogen, the boron diffusivity in its SiO2 increased to levels more than two orders of magnitude greater than that reported in SiO2 annealed under hydrogen without a SiN cap. Nevertheless, the activation energy for boron diffusion in SiO2 in a SiN-capped sample was the same as that for boron diffusion in SiO2 annealed under hydrogen. This indicates that SiN-enhanced boron diffusion can be explained by the model proposed for hydrogen-induced boron diffusion: hydrogen termination of defects reduces the activation energy for interstitial-mediated diffusion of boron in SiO2. Anomalous boron diffusion in SiO2 in SiN-capped samples is thought to result from the SiN film facilitating the incorporation of a large amount of hydrogen in the SiO2. (c) 2004 Elsevier B.V. All rights reserved.

Monitoring of proteins on biosensor surfaces is required for developing high performance biosensors. In this study, distributions of proteins, protein A and immunogloblin G (IgG), immobilized on glass plates were monitored by means of a new protein monitoring technique using time-of-flight secondary ion mass spectrometry (TOF-SIMS) that provides specific chemical imaging. The TOF-SIMS spectra of the protein immobilized on glass plates were analyzed by means of mutual information to select the appropriate fragment ions related to each protein for chemical imaging of proteins. Finally the distributions of protein A and IgG are obtained respectively with this method.

Monitoring of protein distribution on material surfaces is required for developing high performance materials. In this study, distributions of protein A immobilized on glass plates were monitored by means of a new protein monitoring technique based on time-of-flight secondary ion mass spectrometry (TOF-SIMS), which provides specific chemical imaging. Especially for protein analysis, appropriate analysis techniques of TOF-SIMS data are required for discrimination among proteins because most of fragment ions from proteins by TOF-SIMS are the same. In this study information entropy was applied to characterize TOF-SIMS spectra of protein samples containing similar fragment ions. Mutual information, calculated as subtraction of a posteriori information entropy from a priori information entropy indicates specific secondary ion peaks related to a certain protein in spectra. TOF-SIMS spectra and images of the protein immobilized on glass plates were obtained with TFS-2100 (Physical Electronics). TOF-SIMS spectra were analyzed by this method and then specific fragment ions from protein A and glass plates, respectively, are selected according to values of mutual information. With specific fragment ions of each protein, TOF-SIMS image of each protein was obtained. Distributions of protein A on glass plates are obtained with this method.

In order to estimate surface functions of biosensors, surface analytical tools such as time-of-flight secondary ion mass spectrometry (TOF-SIMS) are required for evaluating, identifying and quantifying the biochemical structures of biosensor surfaces. Surface of an optic immunosensor that uses the enhancement of fluorescein isothiocyanate (FITC) fluorescence caused by reactions between proteins, was investigated with TOF-SIMS for estimating and modifying the protein immobilization processes. Secondary ion images of TOF-SIMS show that protein distribution on the sensor surface is not homogeneous. The results indicate that the fluorescence background may be high when proteins are localized on specific area on the biosensor, because a part of immobilized proteins, covered with other proteins, are not able to contribute the reaction with immunoglobulin G (IgG). Thus the estimation of protein immobilization on the biosensor surface with TOF-SIMS clarifies the performance of the biosensor and will contribute to the development of biosensors.

Accurate SIMS measurement of a boron profile in a SiO<Sub>2</Sub>-Si interfacial region under optimum incident angle of low-energy primary oxygen ion beam was made in order to demonstrate the mechanism of boron penetration through gate oxide. Degrees of ionization of Si and boron became almost equal in SiO<Sub>2</Sub> and Si at the 20-degree incident angle with a practical sputtering rate. The estimation of an apparent shift of a boron profile toward surface and the determination of the SiO<Sub>2</Sub>-Si interface under measurement conditions achieving matrix-independent degree of ionization of Si were also examined. The SIMS measurement using optimum conditions revealed that the variation of flat band voltages was proportional to the variation of penetrating boron doses in the range of 0.85−1.30 V. It was also found that when a penetrating boron dose was equivalent to a flat band voltage over 1 V, the electrical activation of boron was lower than that of boron ion-implanted in a Si substrate.

The variation of hydrogen distribution at the SiO2/Si interface by low-temperature hydrogen annealing was investigated using secondary ion mass spectrometry (SIMS). As the amount of hydrogen atoms incorporated at SiO2/Si is considered to be comparable to the silicon dangling bond density (1 x 10(10) to 1 x 10(12) atoms/cm(2)), an analytical method with a high sensitivity is necessary for the detection of hydrogen at SiO2/Si. In this study, the experimental conditions of SIMS were optimized in order to obtain a sufficient reproducibility of interfacial hydrogen ion intensity. There are two main causes that influence the measurement reproducibility: (1) misalignment of the relative irradiation areas of the electron beam and ion beam and (2) the contribution of background hydrogen from surface contaminants and residual gas. We obtained a high measurement reproducibility within a 5.5% relative standard deviation (2sigma). This enabled us to observe an increase of hydrogen at SiO2/Si by hydrogen annealing at 400 degreesC, which resulted from the incorporation of hydrogen from the ambient. From the results of nuclear reaction analysis (NRA) and thermal desorption spectroscopy (TDS), it was also found that the incorporated hydrogen had two chemical states. (C) 2003 Elsevier Science B.V. All rights reserved.

Based on the enhancement of fluorescein isothiocyanate (FITC) fluorescence caused by reactions between proteins, we developed a reagentless, regenerable and rapid immunosensing system to determine immunoglobulin G (IgG). Fluorescence intensity of the immobilized FITC depends on IgG concentration, ranging from 10 to 50 mug/ml, specifically, even with co-existing proteins. The response time is 30 min during steady-state measurement and is less than a minute during transient measurement. When the FITC-labeled protein A binds to IgG, the surrounding atmosphere of FITC becomes hydrophobic. Since the fluorescence intensity of fluorescent substances generally increases at a hydrophobic environment, FITC fluorescence intensity increases with the concentration of protein A bonding to IgG. This system is regenerable because the fluorescence enhancement repeatedly occurs every time the immobilized fluorescent reagent is immersed in sample solutions. (C) 2003 Elsevier Science B.V. All rights reserved.

Superoxide (O2-, one of the reactive oxygen species (ROS)) produced in vivo plays various pathphysiological and physiological roles, and thus it is of great importance and value to evaluate quantitatively dynamic changes in superoxide concentration. We thus aimed at developing a superoxide dismutase (SOD)-immobilized sensor. Using a batch cell, the amount of superoxide produced via oxidation of hypoxanthine by xanthine oxidase (XOD) was quantitatively determined based on the measured electrical current. The peak current increased linearly with hypoxanthine concentration (0-100μM, r2 = 0.99). Using a flow cell, the concentration of superoxide produced from the isolated heart of an endotoxin-administered rat was successfully measured. Overall, the new superoxide sensor demonstrated satisfying performance and reproducibility for the tissue-derived superoxide. © 2002 Elsevier Science B.V. All rights reserved.

In the present study, superoxide (O-2) (one of reactive oxygen species) concentration was measured directly using a superoxide dismutase (SOD)-immobilized electrode. Using a batch cell, super-oxide production from oxidation of hypoxanthine with xanthine oxidase (XOD) was determined from current data. Output current and base-to-peak area were linearly with hypoxanthine concentration. Because these results have the same tendensy with absorptiometry using cyto-chrome C which is one of most popular measurement, appropriateness of the electrochemical method in the present study was confirmed.