Boehmite (aluminum oxyhydroxide, BE) selectively adsorbs phosphate ion. Recently, we studied the recovery efficiency of phosphate ion and the adsorption/desorption mechanism by calcining the BE surface in the temperature range of 200∼1150°C. As a result, the amount of phosphate ion adsorbed/desorbed by BE at a calcining temperature of 400∼700°C exhibited a higher value than the BE at other calcining temperatures, and the recovery efficiency of the phosphate ion was 90% or higher. On the other hand, the amount of phosphate ion adsorbed/desorbed onto BE at a calcining temperature of 1100°C or higher exhibited a lower value than the BE before calcining. Based on the phosphate ion adsorption/desorption behavior results, and the XRD and FT-IR results, it was determined that when the calcined BE is suspended in water, water molecules are dissociated, producing hydroxyl groups on the surface, and these hydroxyl groups exchange ions with the phosphate ion, thus the amount of phosphate adsorbed ion reaches a maximum. The phosphate ion adsorbed by BE was adsorbed by a sodium hydroxide solution, just like the BE before calcination. It became evident that by calcining BE, it is possible to obtain an adsorbent with a high phosphate ion recovery efficiency. [DOI: 10.1380/ejssnt.2005.63]

View full abstract

Nano-sized silver particles generated by the evaporation-condensation method were deposited on the silica glass substrate or sol-gel derived silica film to form films, which were annealed at 100 to 500 °C. The surface morphology and optical absorption spectrum of the films thus obtained were observed. Furthermore, nonlinear optical properties of them were estimated using Z-scan technique. Absorption spectrum exhibited a peak due to localized surface plasmon resonance (LSPR), which was drastically shifted toward shorter wavelength side after annealing at 200 °C accompanying with the changing of the surface morphology. The nonlinear refractive index, γ, of silver films was negative, and its absolute value was decreased with increasing the annealing temperature. The largest contribution of LSPR resulted in the enhancement of γ when annealed at 100 °C. [DOI: 10.1380/ejssnt.2005.120]

View full abstract

The Si(111)-c(12×2)-Ag surface phase was observed by scanning tunneling microscopy (STM) at 65 K and its atomic structure was analyzed in detail. The phase is the ground-state structure within the framework of 'Honeycomb-Chain Channel' reconstruction, attained through successive phase transitions by cooling from 3×1 (> ca. 500 K) and 6×1 phases (> ca. 100 K). The transitions are likely order-disorder types with two-step freezing of fluctuation of the Ag atom positions. [DOI: 10.1380/ejssnt.2005.151]

View full abstract

Dewetting of a polymer solution was used to prepare micrometer-sized 'domes' of polymers. Co-casting two different cyanine dyes led to the incorporation of the dyes into the microdomes. Fluorescence microscopy and micro-spectroscopy was used to determine the aggregation state of the dyes within the microdomes. Bleaching experiments revealed that the dyes form hierarchic structures: dye molecules form sub-micrometer J-aggregates, which in turn align at the edge of micrometer-sized domes that form 2-dimensional arrays. Furthermore, it was found that energy migration occurs between different aggregates. [DOI: 10.1380/ejssnt.2005.165]

View full abstract

A sonicated dispersion of the novel lipid A analog, E5531, was feeze-dried in the presence of various additives such as saccharides and polyalcohols, and their cryoprotective effects were investigated. Fusion of the vesicles was examined by measuring fluorescence energy transfer and size distribution. The ability as cryoprotectants differed among the addtive species. The addition of polyalcohols led to considerable fusion. Although monosaccharides, similar to disaccharides, completely prevented the fusion of the vesicles during lyophilization, they showed far less ability to retain the entrapped calcein in the vesicles compared to disaccharides. Differential scanning calorimetry heating profiles of vesicles that had been lyophilized with various additives were obtained. Disaccharides and monosaccharides again resulted in markedly different thermal properties of the vesicles. This variety in cryoprotective ability of saccharide species can be attributed to differences in their interaction with the E5531 head group. [DOI: 10.1380/ejssnt.2005.169]

View full abstract

The influence of surface states on photoelectron emission phenomena was investigated to determine the work function precisely. A new method for analyzing the yield spectra of photoelectron emission as a function of temperature has been developed. This method was used to decide the work function and surface state of aluminum metal sheets mechanically scratched and ultrasonically cleaned in organic solvent. The yield spectrum as a function of photon energy exhibited a greatly changed shape with an increase and subsequent decrease in temperature in flowing Q gas under the irradiation of 220 nm wavelength light. The ionization energy of a surface state generated at the surface by the influence of temperature and light was estimated. [DOI: 10.1380/ejssnt.2005.179]

View full abstract

Schizophyllan (SPG) is a natural β-(1→3)-D-glucan existing as a triple helix in water and as a single chain in dimethylsulfoxide (DMSO), respectively. As we already reported, when a homo-phosphodiester polynucleotide [for example, poly(dA) or poly(C)] is added to the SPG/DMSO solution and subsequently DMSO is exchanged for water, SPG forms a complex with the polynucleotide. One of the potential applications of this novel complex is an antisense-oligonucleotide (AS ODN) carrier. The present paper describes a modification technique which enables us to introduce transferrin to the reducing end of SPG (Tf-SPG). We made a complex from Tf-SPG and AS ODN and carried out an in vitro antisense assay. We found that Tf-SPG dramatically enhances the antisense effect. Their superiority can be ascribed to enhancement of endocytosis due to the attached transferrin. One of the peculiar features of our system is that the complex (i.e., carrier + AS ODN) is charged negatively in total, because SPG itself is a neutral polysaccharide. This feature is different from the conventional systems such as cationic liposomes and polycations. The present work has thus clarified that SPG can act as a new potential candidate for AS ODN carriers. [DOI: 10.1380/ejssnt.2005.195]

View full abstract

Phase transition of Si(111)-√3×√3-Ag surface has been investigated in the temperature range from 103 K to 293 K using reflection high-energy positron diffraction. Temperature dependences of the diffraction spot intensities below the critical temperature (T_c=116 K) are well explained in terms of the disordering of the inequivalent triangle (IET) structure. From the structure analyses of the rocking curves obtained above and below T_c based on the dynamical diffraction theory, it is concluded that the order-disorder phase transition takes place. [DOI: 10.1380/ejssnt.2005.228]

View full abstract

Indium was deposited onto the Si(111)-7× 7 reconstruction in order to form an ordered array structure of In nanoclusters. Using scanning tunneling microscopy, the annealing effects on the 0.12-monolayer (ML)-In nanoclusters and 0.24-ML-In nanoclusters have been investigated. In the case of 0.12-ML-In, four types of adsorption mechanism including the clustering of In atoms are observed after annealing at 300°C, while, in the case of 0.24-ML-In, almost all In nanoclusters are maintained after annealing at 300°C. This discrepancy is discussed with the relation between the substitution of In for Si adatoms and the clustering of In atoms. [DOI: 10.1380/ejssnt.2005.244]

View full abstract

The frictional behavior of the C₆₀ intercalated graphite films with a large size of 2.3 × 2.3 mm² is reported. The C₆₀ intercalated graphite films consist of alternating close-packed C₆₀ monolayers and graphite layers (graphenes), and thus infinite sliding planes are formed between each C₆₀ monolayer and graphene. The intercalation of C₆₀ molecules into graphite films results in superlubricity where both static and dynamic frictional forces are observed to be zero. [DOI: 10.1380/ejssnt.2005.21]

View full abstract

We focus on a variant of the heme protein, i.e., the recently discovered neuroglobin (NHb) and cytoglobin (CHb), looking for clues with regard to possible applications in polymer electrolyte fuel cells (PEFCs), in a quest to design nanomaterials that would replace the expensive platinum catalysts used in PEFC electrodes. The active heme sites of these two new members of the globin superfamily display a functionally-relevant heme iron atom, whose sixth coordination site is occupied by an endogenous (internal) protein ligand, in the absence of exogenous (external) ligands, such as O₂, CO, and NO. Density Functional Theory (DFT)-based calculation results indicate a possible means of controlling the adsorption and desorption on adsorbed O₂ through the endogenous protein ligand occupying the sixth coordination site of the central iron atom in the heme structure. [DOI: 10.1380/ejssnt.2005.233]

View full abstract

We investigate the stable structures and magnetic properties of Fe-filled single-walled carbon nanotubes (SWNTs) on Ni(111) using first principle calculations. For the two different initial positions of Fe atom inside the nanotube, we find stable geometries and electronic states for the SWNT on Ni(111). When the Fe wire is near the Ni surface, SWNT transforms into arch-like structure. We propose the possibility that the C-C bonds of carbon nanotube are broken by Fe wire and Ni surface. [DOI: 10.1380/ejssnt.2005.266]

View full abstract

We provide a description of the Platinum Porphyrins (PtPor) system and its interaction with O₂ by density functional computations. We compared the geometries based on our calculations to experimental data obtained by x-ray diffraction and also compared our energy states to experimental electronic spectra. Both show good agreement with experiments. We analyzed the electronic characteristics of PtPor and also studied the interaction of O₂ with PtPor. We show that there is an interaction between PtPor and O₂. This can be attributed to the donation of electrons from the occupied 5d_Z² orbitals of Platinum to the 3p-antibonding orbitals of O₂. [DOI: 10.1380/ejssnt.2005.473]

View full abstract

The technology of solid phase growth of multilayer structures with buried nanosize magnesium silicide clusters has been developed. Basing on the experimental data, a conclusion was made that magnesium silicide clusters remain in depth of the Si layers at 650°C and give a contribution in the effective dielectric permeability and effective electron number of multilayer structures. The huge increase of a thermoelectric power coefficient for samples with buried magnesium silicide clusters in comparing with one for the bare p-type silicon substrate has been observed. [DOI: 10.1380/ejssnt.2005.12]

View full abstract

The submonolayer Al/Si(111)7×7 system has been studied by our group using scanning tunneling microscopy and total-energy calculations. We present a review of our recent results on the formation mechanisms and structural properties of the main reconstructions developed on the Si(111)7×7 surface upon Al adsorption, including α-7×7, √3×√3, √7×√7 and γ-phase. [DOI: 10.1380/ejssnt.2005.55]

View full abstract

Processes of β-FeSi₂ nanosize islands growth on Si(111)7× 7 surface and Si(111)-Cr surface phases and silicon growth over β-FeSi₂ nanosize islands have been studied by LEED, in situ electrical measurements and ex situ atomic force microscopy. The close matching of electric parameters of silicon with buried iron disilicide clusters and Si(111)7× 7-Cr surface phases proves minimal carrier scattering on these clusters. Thermoelectric measurements of buried β-FeSi₂ islands revealed a very high value of the thermoelectric power coefficient as compared with p-type clean silicon. [DOI: 10.1380/ejssnt.2005.97]

View full abstract

Through electron diffraction observations, we found a √21× √21 phase formation by Na adsorption of 0.1∼ 0.2 ML on a Si(111)√3× √3-Ag surface below 250K. Its electronic structure was investigated by angle-resolved photoemission spectroscopy using synchrotron radiation. The phase was found to be metallic. At least six different states were identified as surface states within the bulk band gap, whose dispersions were determined along a primary symmetry direction. The observed two-dimensional band structure had a very close resemblance with those of √21× √21 phases induced by noble-metal adsorption on the same substrate. [DOI: 10.1380/ejssnt.2005.107]

View full abstract

The methods of Differential Reflection Spectroscopy (DRS) and Atomic Force Microscopy (AFM) have been applied to study early stages of β-FeSi₂ silicide formation. Some details on the Dynamic Standard method in DRS are presented. The imaginary part of the dielectric function of the β-FeSi₂ film during its formation are calculated. [DOI: 10.1380/ejssnt.2005.113]

View full abstract

Formation of thallium overlayers on the Si(100)2 × 1 surface has been studied using first-principles total-energy calculations. According to total-energy calculations and STM image modeling, thallium atoms should occupy the following positions on Si(100) surface: (i) valley-bridge (0.25 ML of thallium coverage); (ii) parallel Tl-Tl dimer in valley-bridge (0.5 ML); (iii) pedestal, valley-bridge and valley-bridge (0.75 ML); and (iv) pedestal and valley-bridge (1.0 ML). The simulated STM images are in good agreement with experimental data [A.A. Saranin et al. Phys. Rev. B 71, 035312 (2005)]. The possible atomic mechanism of reconstruction alternation is discussed. [DOI: 10.1380/ejssnt.2005.125]

View full abstract

We have successfully measured the sliding force for an interlayer of individual multiwall carbon nanotubes using a combination of a well-controlled electrical breakdown process and a manipulation process using a scanning electron microscope. A sliding force of ∼4 nN for an inner layer diameter of 5 nm is maintained constant during a sliding process. This result agrees well with the theoretical calculation. This agreement indicates that the layered structure exhibits ideal characteristics even after the electrical breakdown process. We have also proposed nanoscale variable resistors using the sliding mechanism of the interlayer of individual multiwall carbon nanotubes. The two-terminal resistance of the processed nanotube increases exponentially with the sliding distance under a low bias voltage and is proportional to the sliding distance under a high bias voltage. The variation of the resistance under the low bias voltage can be explained as a one dimensional localized system, with a characteristic localization length around 840 nm. On the contrary, the sliding nanotube acts as the diffusive conductor under a high bias voltage. [DOI: 10.1380/ejssnt.2005.86]

View full abstract

Chains of crystalline-Si nanospheres (Si nanochains), in which Si nanocrystallites are connected by amorphous Si oxide periodically in nearly equal spacing forming a chain-like one-dimensional structure, have been fabricated via a self-organized formation process. In this paper, we review our recent studies and extend results on structural analysis, formation mechanism and properties of Si nanochains. The structure have been revealed by transmission electron microscopy-based approaches including high-resolution imaging, energy-filtered imaging and energy-dispersive x-ray fluorescence analysis. The one-dimensional growth was attributed to the well-known vapor-liquid-solid mechanism. A formation mechanism of the chain-like structure was proposed: periodical change in diameter in Si nanowire growth and self-limiting surface oxidation during growth. The former was evidenced through numerical simulations of nanowire growth catalyzed by a molten droplet, and the latter through energy-filtered transmission electron microscopy observations. We also developed a method of high-yield chain growth by adding metal impurities such as Pb to the Au catalyst. By adding such metal impurities, a periodic instability in the wetting angle of the catalysts was promoted. Using the dense chain samples, we observed a phonon-confinement effect in the Si nanocrystallites by Raman scattering and also found that the Si nanocrystallites in the nanochains were under compressive stress. We also observed photoluminescence in visible-light region, and the luminescence was tentatively attributed to the exciton recombination in the Si oxide. Electronic transport property of the Si nanochains characterized well the chain-like feature: staircases were observed in I-V curves. The result opens possibility that Si nanochains can be used as components of single-electron devices. Finally, it was demonstrated that more complex nanostructures can be fabricated using Si nanochains as templates. [DOI: 10.1380/ejssnt.2005.131]

View full abstract

Low molar mass liquid crystals formed dewetted island, or 'dome' structures when cast from dilute solution on substrates. Hexaalkoxytriphenylene formed hexagonal micronsize islands when the cast film was slowly cooled from the isotropic state. Co-casting of cyanine dyes led to hierarchic structures of fluorophores in the center of the domes, and fluorescence microscopy and microspectrometry confirmed that cyanine J-aggregates were formed. [DOI: 10.1380/ejssnt.2005.156]

View full abstract

Biomolecule-nanoparticle (NP) hybrid systems provide functional assemblies for the construction of sensors, nanocircuitry and devices. The development of sensors based on functionalized NPs will be exemplified with the electrical contacting of glucose oxidase with Au NPs (1.4 nm) functionalized with the FAD cofactor, and with the optical detection of telomerase activity in cancer cells using CdSe-ZnS core-shell NPs. Also, the formation of shaped Au NPs exhibiting longitudinal red-shift absorbance will be used to follow NAD⁺-dependent biocatalytic reactions. The use of biomolecule-NP hybrid systems for nanocircuitry and devices is addressed by the polymerization of Au-NPs functionalized G-actin followed by the catalytic enlargement of the filaments to generate continuous, conductive Au-nanowires. Sequential polymerization of Au-NP-modified G-actin and G-actin yields patterned nanowires with motor functions. The immobilization of the filaments on a myosin interface results in the motility of the filaments upon addition of the ATP fuel. The nano-objects move on the surface at a speed corresponding to 250 nm·sec^-1. [DOI: 10.1380/ejssnt.2005.1]

View full abstract

Hydrogels are made of swollen polymer networks containing more than 90% water. If modified with free chains on their surface, gels exhibit low surface friction and thus have been attractive candidates as artificial cartilage and low frictional materials. However, most hydrogels are mechanically too weak to be used as any load bearing devices. We have overcome this problem by synthesizing hydrogels with a double network (DN) structure. Despite of 90% water, these tough gels exhibit a fracture stress of 170 kg/cm², similar to that of cartilage. Extremely high mechanical property is due to peculiarly inhomogeneous structure of DN gels. The inhomogeneous structure is thought that large 'voids' of the first network may exist, and the second polymers exist in 'voids' of first network act as 'molecular crack-stopper' in DN gels, keeping the crack from growing to a macroscopic level. [DOI: 10.1380/ejssnt.2005.8]

View full abstract

As a model for electron processes in organic thin films, carrier generation after photoexcitation of organic photoconductors was studied by the time-resolved infrared spectroscopy. A broad transient absorption was observed in the IR range after a photocarrier generation. We ascribed all these transients to the cationic species of a charge transport material (CTM) from the results of the measurements in various conditions. The transient absorption spectrum showed remarkable dependence on the CTM concentration. From this observation, we concluded that the cationic species of CTMs were monomer, dimer and larger aggregate cations. The latter two cationic species are regarded as the holes delocalized within some CTM molecules. Based on these observations, carrier generation mechanism in organic photoconductors is discussed. [DOI: 10.1380/ejssnt.2005.24]

View full abstract

Meso-tetraphenylporphyrin derivative having four thioacetyl groups was synthesized using Lindsay's method. Monodisperse small gold (Au) nanoparticles passivated by the synthesized ligand were prepared by a liquid phase synthesis. The nanoparticles were extremely stable and can be homogeneously dispersed in basic aqueous solution. [DOI: 10.1380/ejssnt.2005.30]

View full abstract

Tools for selective recognition and sensing of kinase-catalyzed phosphorylation at tyrosine or serine/threonine residues located on the protein surface are essential for understanding signal transduction cascades of living cell. A stable complex of RNA and peptide (ribonucleopeptide) provides a convenient approach to tailor a receptor for small molecules. In vitro selection of an RNA-derived pool of ribonucleopeptide afforded a ribonucleopeptide receptor specific for phosphotyrosine. The phosphotyrosine-binding ribonucleopeptide receptor discriminated phosphotyrosine against tyrosine, phosphoserine and phosphothreonine. [DOI: 10.1380/ejssnt.2005.33]

View full abstract

Schizophyllan is a natural β-(1→3)-D-glucan existing as a triple helix in water and as a single chain in dimethylsulfoxide (DMSO), respectively. As we already reported, when a homo-polynucleotide [ex. poly(A) or poly(dA)] was added to the schizophyllan/DMSO solution and subsequently DMSO was exchanged for water, the single chain of schizophyllan formed a complex with the polynucleotide. In this paper, using an adenine-thymine (or uracil) double strand as a model system, we explored whether s-SPG can unzip the polynucleotide duplexes, examining the competition between the schizophyllan/polynucleotide complexation and the polynucleotide hybridization with circular dichroism and fluorescence spectroscopy at various NaCl concentrations. The unzipping reaction happened for the hetero-duplexes (i.e., RNA-DNA duplexes) at low salt concentrations, on the other hand, it was not observed for the homo-duplexes at all the salt concentrations. When we compared dissociation temperatures, the unzipping reaction of the homo-duplexes was expected at low salt concentrations. This discrepancy between the experimental results and the expectation, as well as the different behavior between the hetero- and homo- duplexes, can be ascribed to the difference in the activation energy of intermediate states. [DOI: 10.1380/ejssnt.2005.38]

View full abstract

In order to detect and visualize the electrostatic features of biological macromolecules in a non-contact mode, we have refined the technique of scanning probe microscopy. The forces in the sub-piconewton range between the probe stylus and the sample surfaces have been measured with a gap distance controlled with nanometer accuracy. Images of the electrostatic surface forces of myosin filaments were detected in pure water using positively charged whiskers as cantilever probe tips. The images were consistent with the structure of myosin filaments that have a bipolar spindle shape; they were charged with a great number of negative charges in the central bare zone compared with the rest of the filament. Thus, in this non-contact mode, the electrostatic features of the protein surface rather than the surface topography were measured. This method has been further extended to measure forces exerted between protein molecules. Long-range interaction between kinesin and microtubules has been examined. It is likely that long-range attractive forces, in the order of several nanometers, exist between kinesin and microtubules. [DOI: 10.1380/ejssnt.2005.46]

View full abstract

There are two basic differences in the motion between a human-made machine and a biological motor. One is in their principles. The motion of a human-made machine, which is constructed from hard and dry materials such as metals, ceramics or plastics, is realized by the relative displacement of the macroscopic constitute parts of the machine. In contrast to this, the motion of a living organism, which consists of soft and wet protein and tissues, is caused by the molecular deformation that is integrated to a macroscopic level through its hierarchical structure [1−3]. The other is in their energy sources. The human-made machine is fueled by electrical or thermal energy with efficiency around 30%, but a biological motor is driven by direct conversion from the chemical energy with efficiency as high as 80-90% [4]. In order to create biomimetic motility systems, polymer gels have been employed using their reversible size and shape change, thereby realizing the motion by integrating the deformation on a molecular level. Along this line, several kinds of artificial soft machines have been constructed using synthetic polymer gels in the past years. Gelooper (gel-looper), gelf (gel golf), gel valves, chemical motor, etc., are examples [5−11]. However, the lack of hierarchical structures and energy sources inside the gel lead to a decreased response and restricts the further application of such actuators for practical use in human bodies. Here we report an ATP fueled soft gel machine reconstructed from muscle proteins of actin and myosin. Chemically cross-linked actin gel filaments, several decade times the length of native actin filaments (F-actin) move along a chemically cross-linked myosin fibrous gel (1 cm long and 50 μm in diameter) with a velocity as high as that of native F-actin, by coupling to ATP hydrolysis. The motility observed in muscle protein-gels suggests that one might reconstruct a soft machine fueled by chemical energy by using actin and myosin molecules as elementary elements. [DOI: 10.1380/ejssnt.2005.51]

View full abstract

The purpose of this study is to develop an apparatus for simultaneous measurement of electrical and spectroscopic parameters of single ion-channels. We have combined the single channel recording apparatus with an artificial lipid bilayer and a fluorescence microscope designed to detect single fluorescent molecules. The artificial membranes were formed on a PEG (polyethylene glycol)-coated glass and observed with an objective-type total internal reflection fluorescence (TIRF) microscope. The lateral motion of a single lipid molecule (β-BODIPY 530/550 HPC) was recorded. The lateral diffusion constant of the lipid molecule was calculated from the trajectories of single molecules as D=8.0± 4.0× 10^-8 cm²/s. Ionic channels were incorporated into the membrane and single-channel current fluctuations were recorded. These data show the possibility of the present technique for simultaneous measurement of electrical and spectroscopic parameters of single-channel activities. [DOI: 10.1380/ejssnt.2005.70]

View full abstract

We report the direct observation of optically forbidden energy transfer between cubic CuCl quantum dots via an optical near-field interaction using time-resolved near-field photoluminescence (PL) spectroscopy. The energy transfer time and exciton lifetime were estimated from the rise and decay times of the PL pump-probe signal, respectively. We found that the exciton lifetime increased as the energy transfer time fell, which strongly supports the notion that near-field interaction between QD makes the anti-parallel dipole coupling. Namely, a quantum-dots pair coupled by an optical near field has a long exciton lifetime and optically forbidden features due to its anti-parallel electric dipole pair. [DOI: 10.1380/ejssnt.2005.74]

View full abstract

We report here development of ultra-small reaction chamber array from silicone-elastomer sheet and glass plate, and its applications for biological assay. It was shown that single-molecules of protein, or DNA can be enclosed in each hermetic chamber stably. The volumes of chambers are extremely small (6∼10 femtoliters) so that small numbers of molecule (∼2000) can reach to detectable concentrations (∼micro molars). When single enzyme molecules were enclosed in the chambers, its catalytic activity was fluorescently monitored to demonstrate the feasibility of single-molecule assay using the chamber. We also apply this method to access reaction efficiency of protein molecular motor, F₁-ATPase. Motor molecules were enclosed and manipulated to rotate reversely using magnetic tweezers. The resultant extremely small amount of synthesized ATP was calculated from the speed of the motor after released from the manipulation. This measurement revealed first time that the motor is designed to tightly couple the chemical reaction and mechanical event. Thus, it was proven that the ultra-small chamber can be a new strong tool for ultra-sensitive bioassay. [DOI: 10.1380/ejssnt.2005.79]

View full abstract

For the purpose of the fabrication of nanowires, the metallization of double-stranded DNA by the selective electroless plating method was investigated. Cis-platin was bound to template DNA molecules and reduced to platinum which can catalyze subsequent silver metal deposition. We have found that when DNA-amphiphile polyion complex monolayer, which was formed at the air-water interface, was transferred to a glass substrate by using the Langmuir-Blodgett (LB) method, DNA molecules could be immobilized and stretched on the glass substrate. The DNA molecules combined with the platinum clusters was also stretched and immobilized on a glass substrate by using the LB method. The electroless plating of the platinum-bound DNA molecules immobilized on the substrate by reduction of silver ion gave uniform silver nanowires (c.a. 50nm in width and height) along the stretched DNA structures. On the contrary, the electroless plating of DNA molecules without the catalyst provided inhomogeneous silver deposition. [DOI: 10.1380/ejssnt.2005.82]

View full abstract

Fluorescence microscopy and scanning nearfield optical microscopy and spectroscopy were used to characterize cyanine dyes adsorbed to mica surfaces. The formation of J-aggregates was confirmed, and furthermore it was found that the J-aggregates show a fluorescence-intensity dependent spectral shift. Brighter, and thus larger aggregates show a red-shift in fluorescence spectra of up to 3 nm. [DOI: 10.1380/ejssnt.2005.94]

View full abstract

Potential-driven movements of a surface-modified Au nanoparticle at a Au(111) electrode/aqueous solution interface were examined. An interfacial capacity peak due to the reorientation of terminal 4-pyridyl groups of the surface modifier layer was observed when the Au(111) electrode was touched to the spread film of the particles on the surface of an aqueous solution at lower surface pressures than equilibrium spreading pressure. When the spread amount was increased, appearance of a capacity response presumably due to partial adsorption-desorption of the particles was observed. Implications of the results of electrochemical and electroreflectance measurements were discussed in regards to the reversible movement of the particles. [DOI: 10.1380/ejssnt.2005.141]

View full abstract

We present here a novel approach to organization of an α-helical hydrophobic polypeptide complex in lipid bilayers in a 'lipid-domain-selective' manner. The key strategy is to use disulfide linkage between a cysteine-bearing polypeptide and a disulfide-based phospholipid, the latter of which forms a phase-separated lipid domain in a binary lipid bilayer with an incompatible phospholipid lacking disulfide group. The cross-linkage between the polypeptide and the phospholipid can be expected that the polypeptide acquires a higher affinity to the disulfide-based lipid domain than to the other one, resulting in selective distribution of the polypeptide in the former domain. The polypeptide analogous to a photosynthetic bacterial light-harvesting polypeptide binds a pigment, zinc-substituted bacteriochlorophyll a ([Zn]-BChl a), to form the light-harvesting polypeptide/pigment complex. The complex was incorporated into an incompatible binary lipid bilayer combination either the disulfide-based phospholipids bearing oleoyl chains (DO-DO)/1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) or 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)/DSPC. The lipid-domain-selective organization was confirmed by fluorescence resonance energy transfer (FRET) from a rhodamine-labeled lipid (Lissamine rhodamine B 1,2-diacyl-sn-glycero-3-phosphoethanolamine: either N-Rh-DOPE or N-Rh-DSPE) to the assembled [Zn]-BChl a. Considering the relative affinity of these fluorescent lipid probes, N-Rh-DOPE and N-Rh-DSPE prefer to fluid and gel domains, respectively, because of the similarity of their acyl chains. When the fluorescent lipid probe, N-Rh-DOPE, was applied to the binary lipid system, DO-DO/DSPC, the higher FRET efficiency was observed compared to the counterpart FRET assay using N-Rh-DSPE. In contrast, for the DOPC/DSPC bilayer, the difference in the FRET efficiency between the fluorescent lipid probe systems was negligible. These results suggest that the polypeptide/pigment complex is preferentially incorporated into the disulfide-based lipid domain. Total internal reflection fluorescence (TIRF) microscopic observation of the assembly also evidenced heterogeneous structure by detection of fluorescence from [Zn]-BChl a. [DOI: 10.1380/ejssnt.2005.145]

View full abstract

In tissue engineering, micro/nanofabrication is important to modify substrate surfaces for regulating the attachment and growth of cells. In neuroscience, it is significant for neural regeneration; this involves guiding and extending dendrites and axons by a cell culture scaffold which acts as an extra cellular matrix. In this study, we prepared highly regular porous honeycomb-patterned films by a simple casting technique and cultured neurons to investigate their morphologies on the patterned films. The morphologies of neurons were examined by a scanning electron microscope and a confocal laser scanning microscope. The neurons were round and the neurites extended randomly on the flat film. The patterns influenced the morphologies of neurons. The morphologies of neurons were changed by varying the pore size of the honeycomb- patterned films. The neurites spread along the rims of the honeycomb pattern. These results suggest that the self-organized honeycomb-patterned films are useful biomaterials for neural tissue engineering. [DOI: 10.1380/ejssnt.2005.159]

View full abstract

To establish a DNA sensor, DNA self-assembled monolayer (SAM) was prepared on a gold substrate. A probe DNA SAM was fabricated using thiolated DNA composed of single- and double-stranded portions on a gold substrate. The adsorption behaviors of probe DNAs were measured by surface plasmon resonance (SPR). Hybridization efficiency was optimized by controlling the length of spacer inserted in probe portion and SAM layer. Hybridization with target DNA on the DNA array prepared using probe DNA was monitored in situ by SPR imaging. The SPR image indicates that 10-thymine bases spacer shows the most efficient hybridization on the DNA array. [DOI: 10.1380/ejssnt.2005.250]

View full abstract

The adsorption of the plasma protein fibrinogen on model hydrophobic surfaces has been explored using atomic force microscopy. Images of fibrinogen adsorbed on both graphite and methyl-terminated self-assembled monolayers are both observed to be highly non-uniform. On both substrates, aggregation and clustering of the fibrinogen molecules is seen. In the case of the graphite surface, we observe a strong preference for adsorption at atomic level steps in the graphite structure. In addition, a region free of protein adsorption is often observed near the step edges. Based on the size of this protein-depleted region, we estimate that the fibrinogen molecules must have diffusion lengths on the order of ∼200 nm under the conditions of these experiments. These results suggest that in the initial stages of adsorption, fibrinogen is quite mobile on a hydrophobic surface. [DOI: 10.1380/ejssnt.2005.173]

View full abstract

We present results showing that silicon substrates can be used as a universal platform for recording the electrical activity of ion channels inserted into suspended bilayer membranes. The bilayers span 150 μm apertures etched into silicon substrates using standard microelectronics processing techniques. The silicon is oxidized, patterned with a 75 μm thick SU-8 epoxy resist and then coated with a thin layer of polytetrafluoroethylene rendering the surface hydrophobic. Reversible Ag/AgCl electrodes are integrated around the circumference of the opening and provide long-term stable measurements of the ion channel currents. Characteristic measurements of OmpF porin ion channel protein in phospholipid bilayers and α-hemolysin toxin protein in triblock copolymer layers were made. Long-term measurements showed that ion channel activity could be recorded 22 hours after initial formation of a lipid bilayer. [DOI: 10.1380/ejssnt.2005.184]

View full abstract

We proposed and fabricated vertical micro reactor stack with vertical fluid flow operation available for the environment analysis, post-genome analysis, gene diagnosis, and screenings of the useful materials for the medicine manufacture. This reactor is characterized as the simple structure and new aspects of the vertical fluid transportation evoked by the use of the fluid filter with micro through-bores. The LIGA process using synchrotron radiation was applied for the fabrication of the fluid filters. The CFD simulation results suggested that the fluid can be held by the fluid filter and easily transported by the pneumatic operation. It was also confirmed that the fluid flow velocity through the filter was controlled by varying the loaded pressure around several kPa. Furthermore, it was expected that the fluid was stirred and mixed when passing through the fluid filter. It was demonstrated that a proposed chemical reactor had a good performance of the vertical fluid flow operation and chemical reaction. [DOI: 10.1380/ejssnt.2005.190]

View full abstract

The efficient analysis of the function of ion channels is an important task in many different fields ranging from (bio)analytics and drug-screening to nanoelectronics. Here, the modulation of the channel activity of a synthetic ligand gated ion channel by a specific antibody is measured in tethered lipid bilayers by impedance spectroscopy. Tethered single lipid bilayers with exceptionally high electrical resistances suitable for the detection of a few channels are presented. [DOI: 10.1380/ejssnt.2005.203]

View full abstract

Heme containing peroxidase, for example manganese peroxidase (MnP), is easily inactivated by the hydrogen peroxide (H₂O₂) presented in the reaction. Here we extremely increased the H₂O₂ stability of MnP by molecular evolution and immobilization in mesoporous materials. A mutant MnP library containing three randomized amino acid residues located in the entry site of H₂O₂-binding pocket of MnP was evolved on a 384-well plate using SIMPLEX (single-molecule PCR-linked in vitro expression). The screening of more than 10⁴ samples independently expressed for improved H₂O₂ stability led to four positive mutants, the H₂O₂ stability of which was nine times higher than that of the wild-type. Immobilized MnP mutant in mesoporous material (FSM) showed the high H₂O₂ stability, more than 50 folds than wild type MnP. But the stability of immobilized wild type MnP was not improved so much as that for immobilized mutant MnP. [DOI: 10.1380/ejssnt.2005.207]

View full abstract

The effects of annexin 5 on the lateral diffusion of single molecule lipids and single molecule proteins were studied in a lipid bilayer membrane. Single β-BODIPY HPC and ryanodine receptor type 2 (RyR2) labeled with Cy5 molecules were monitored by fluorescence microscopy. The diffusion coefficient was calculated in the presence and absence of annexin 5. The diffusion coefficients of β-BODIPY HPC and RyR2 were 11 × 10^-8 cm²/s and 2.7 × 10^-8 cm²/s in the absence of annexin 5, respectively. The diffusion coefficients of β-BODIPY HPC and RyR2 in the presence of 1 μ annexin 5 were 2.4 × 10^-10 cm²/s and 2.6 × 10^-10 cm²/s, respectively. Overall, 1 μ annexin 5 decreases the lateral diffusion coefficient 100-500 fold. Regarding RyR2, annexin 5 has little effect on function and can be used to immobilize RyR2 in a lipid bilayer system. [DOI: 10.1380/ejssnt.2005.213]

View full abstract

Giant liposomes or giant unilamellar vesicles (GUVs) of lipid membranes, with diameter greater than 10 μm have a great advantage over smaller liposomes, e.g., large or small unilamellar vesicles, LUVs or SUVs in the investigation of biomembranes. Studies of single GUVs (the 'single GUV method') yield especially useful information on their structure and physical properties as a function of time and spatial coordinates. Here we show three examples of studies using the single GUV method: analysis of shape changes of GUVs; membrane fusion and vesicle fission; and use of a GUV as a microscopic container. [DOI: 10.1380/ejssnt.2005.218]

View full abstract

Single molecular layer of avidin is fabricated on an atomically flat SiO₂ surface and characterized by atomic force microscopy (AFM) and infrared reflection absorption spectroscopy. Immobilization of avidin is performed as follows; i) ester-modification of the surface by silane-coupling agent, ii) carboxylation by hydrolysis in HCl and iii) amide bonding between the surface -COOH and -NH₂ in avidin molecules. Large dome structures (∼60 nm height) are formed after the ester-modification, but an atomically flat surface is obtained after the hydrolysis reaction. AFM topographs and function-recognizing images show that the each of avidin molecules adsorbs as a single molecule and retains the biotin-binding activity. Formation of a tethered bilayer membrane of a biotinylated phospholipid on the avidin layer is also described. [DOI: 10.1380/ejssnt.2005.237]

View full abstract

A compact fluorescence recovery after photo-bleaching (FRAP) apparatus was constructed using a semiconductor laser as an illumination light source. The second harmonic, 560 nm, of the 1120 nm semiconductor laser is guided to the light source point of the fluorescence microscope by an optical fiber. Since the illumination light wavelength 560 nm almost fits to the absorption maximum of the fluorescence dye molecule rhodamine B sulfonyl, the photo-bleaching was induced efficiently with minimum heating of the microscope lens system. The time dependence of the fluorescence recovery was directly measured by the photo-multiplier attached and the diffusion coefficient of the lipid molecules was calculated. [DOI: 10.1380/ejssnt.2005.254]

View full abstract

The coexisting metastable reconstructions of the Si(111) surface have been investigated by non contact-atomic force microscopy (NC-AFM). True atomic resolution has been achieved in the NC-AFM imaging of the 7× 7, c(2× 8), 2× 2, c(2× 4), and √3× √3 coexisting reconstructions of the same quenched surface sample. A simple comparison with scanning tunneling microscopy (STM) results is given, and imaging of 2× 1 π-bonded chains island is also reported. [DOI: 10.1380/ejssnt.2005.258]

View full abstract

We report ultrahigh vacuum scanning tunneling microscopy (UHV-STM) study of the atomic hydrogen adsorption onto a clean Si(113)-3 × 2 surface on an atomic scale. Even after hydrogen exposure of 4 L, STM images reveal clearly that some adatoms are invisible and some pentamers change their image contrast, probably due to hydrogen adsorption at the surface dangling bonds of the corresponding sites. Based on the results of STM together with low-energy electron diffraction (LEED), we discuss the initial adsorption processes of atomic hydrogen on Si(113)-3 × 2 and the transition from 3 × 2 to 3 × 1. [DOI: 10.1380/ejssnt.2005.263]

View full abstract