Surface Enhanced Visible Absorption of Dye Molecules in the Near-Field of Gold Nanoparticles.

Surface enhanced absorption is a plasmonic effect parenting to surface enhanced fluorescence and Raman scattering, and it was clearly reported to occur in the infrared region of the spectrum of light. In this paper, we unambiguously show that it also occurs in the visible region of the spectrum by using a dye; i.e. an azo-dye, which exhibits a good light absorption in that region, and gold nanoparticles, which act as plasmonic nanoantennas that capture and re-radiate light, when the azo-dyes and the nanoparticles are incorporated in the bulk of solid films of polymer. In such a configuration, it is possible to use a dye concentration much larger than that of the nanoparticles and absorption path lengths much larger than those of the molecularly thin layers used in surface enhanced effects studies. In addition, the dye undergoes shape and orientation change; i.e. isomerization and reorientation, upon polarized light absorption; and the observation of surface enhanced visible absorption is done by two separate experiments; i.e. UV-visible absorption spectroscopy and photo-induced birefringence, since the signals detected from both experiments are directly proportional to the extinction coefficient of the dye. Both the dye's absorption and photoorientation are enhanced by the presence of the nanoparticles.

Light-tunable Fano resonance in metal-dielectric multilayer structures.

High-Q optical Fano resonances realized in a variety of plasmonic nanostructures and metamaterials are very much promising for the development of new potent photonic devices, such as optical sensors and switches. One of the key issues in the development is to establish ways to effectively modulate the Fano resonance by external perturbations. Dynamic tuning of the Fano resonance applying the mechanical stress and electric fields has already been demonstrated. Here, we demonstrate another way of tuning, i.e., photo-tuning of the Fano resonance. We use a simple metal-dielectric multilayer structure that exhibits a sharp Fano resonance originating from coupling between a surface plasmon polariton mode and a planar waveguide mode. Using a dielectric waveguide doped with azo dye molecules that undergo photoisomerization, we succeeded in shifting the Fano resonance thorough photo-modulation of the propagation constant of the waveguide mode. The present work demonstrates the feasibility of photo-tuning of the Fano resonance and opens a new avenue towards potential applications of the Fano resonance.

Mechanism of variable structural colour in the neon tetra: quantitative evaluation of the Venetian blind model.

The structural colour of the neon tetra is distinguishable from those of, e.g., butterfly wings and bird feathers, because it can change in response to the light intensity of the surrounding environment. This fact clearly indicates the variability of the colour-producing microstructures. It has been known that an iridophore of the neon tetra contains a few stacks of periodically arranged light-reflecting platelets, which can cause multilayer optical interference phenomena. As a mechanism of the colour variability, the Venetian blind model has been proposed, in which the light-reflecting platelets are assumed to be tilted during colour change, resulting in a variation in the spacing between the platelets. In order to quantitatively evaluate the validity of this model, we have performed a detailed optical study of a single stack of platelets inside an iridophore. In particular, we have prepared a new optical system that can simultaneously measure both the spectrum and direction of the reflected light, which are expected to be closely related to each other in the Venetian blind model. The experimental results and detailed analysis are found to quantitatively verify the model.

Femtosecond laser nano-ablation in fixed and non-fixed cultured cells.

To understand the onset and morphology of femtosecond laser submicron ablation in cells and to study physical evidence of intracellular laser irradiation, we used transmission electron microscopy (TEM). The use of partial fixation before laser irradiation provides for clear images of sub-micron intracellular laser ablation, and we observed clear evidence of bubble-type physical changes induced by femtosecond laser irradiation at pulse energies as low as 0.48 nJ in the nucleus and cytoplasm. By taking ultrathin sliced sections, we reconstructed the laser affected subcellular region, and found it to be comparable to the point spread function of the laser irradiation. Laser-induced bubbles were observed to be confined by the surrounding intracellular structure, and bubbles were only observed with the use of partial pre-fixation. Without partial pre-fixation, laser irradiation of the nucleus was found to produce observable aggregation of nanoscale electron dense material, while irradiation of cytosolic regions produced swollen mitochondria but residual local physical effects were not observed. This was attributed to the rapid collapse of bubbles and/or the diffusion of any observable physical effects from the irradiation site following the laser exposure.

A study of the metabolism of methamphetamine and 4-bromo-2,5-dimethoxyphenethylamine (2C-B) in isolated rat hepatocytes.

The metabolism of methamphetamine (MA) and 4-bromo-2,5-dimethoxyphenethylamine (2C-B) in freshly isolated rat hepatocytes was investigated, and compared with in vivo results. A suspended hepatocyte culture, established from male Wistar rats using a collagenase perfusion technique, was incubated in the presence of MA or 2C-B. After enzymatic hydrolysis of the conjugated forms, the metabolites were extracted by liquid-liquid partition and analyzed by gas chromatography/mass spectrometry (GC/MS). Amphetamine, p-hydroxymethamphetamine and p-hydroxyamphetamine were detected in the culture fluids of the rat hepatocytes inoculated with MA. The alcohol derivative, carboxylic acid derivative, 2-O-desmethyl-2C-B, 2-O-desmethyl-N-acetyl-2C-B and 5-O-desmethyl-N-acetyl-2C-B were detected in the case of 2C-B. The major metabolite of MA in rat hepatocytes was p-hydroxymethamphetamine. This is in good agreement with the urinary excretion profile for rats that were fed MA. 2-O-Desmethyl-2C-B and the carboxylic acid derivative were the major recovered metabolites of 2C-B in the rat hepatocyte culture, a slight deviation from the in vivo findings, in which 5-O-desmethyl-N-acetyl-2C-B was found to be the main component. Metabolites with a hydroxy group were largely present in their conjugated forms in the culture fluids, except for 2-O-desmethyl-2C-B. Taking these results into consideration, a primary hepatocyte culture system has the potential to provide a quick and handy method for estimating the in vivo metabolic fate of abused drugs.

[A statistic study of airborne pollen grains].

Since 1969, authors have been doing a statistical analysis of airborne pollen grains, aiming at the clarification of their atmospheric behaviors, in connection with an increase in a number of pollinosis cases. The airborne pollens were collected three times a week starting from January 1 and ending December 31 with the help of cascade impactor, by which 6001 of air was suctioned at the rate of 51 per min for 2 h from 10:00 a.m. to 12:00 at the rooftop of one of the buildings (16 m high) in the Narashino Campus of Toho University, Funabashi, Chiba. The collected airborne pollens were numerated and classified under microscope according to the Ikuse's classification system for Japanese pollens. The number of days (n) was plotted as a function of daily number of a certain type of airborne pollens (x), not fitting to a simple normal distribution. However, the data were found to approximate a normal distribution when x was log-transformed as ln (x + 1). Among the statistical methods tested, semilogarithmic plot, Weibull plot, Edwards' plot and circular graph method were found to be useful in the follow-up of seasonal variation of environmental pollen grains, especially when used in combination.

Improved extraction procedures for polychlorinated biphenyls in solid samples with aqueous sodium hydroxide under autoclave conditions.

The efficacy of the extraction of polychlorinated biphenyls (PCBs) from varnish-infiltrated insulating papers as a model of solid materials with an aqueous sodium hydroxide (NaOH) by autoclaving at 121 degrees C for 30 min was compared with those for the conventional procedures, i.e., saponification with 1 N ethanolic NaOH in a boiling water bath for 60 min and extraction with benzene in a Soxhlet apparatus. The newly invented autoclaving method was found to be superior to the conventional ones, yielding approximately 5- to 6-fold cumulative PCB congeners without being accompanied by extended decomposition. Therefore, the autoclave-based sample treatment is recommended for more accurate determination of PCBs in the case of PCB-impregnated solid materials such as hardened oils and resin-coated or -infiltrated papers instead of being treated conventionally.

Evanescent field excitation and measurement of dye fluorescence in a metallic probe near-field scanning optical microscope.

We introduce a method of dye fluorescence excitation and measurement that utilizes a near-field scanning optical microscope (NSOM). This NSOM uses an apertureless metallic probe, and an optical system that contains a high numerical aperture (NA) objective lens (NA= 1.4). When the area which satisfies NA < 1 is masked, the objective lens allows for the rejection of possible transmitted light (NA < 1) through the sample. In such conditions, the focused spot consists of only the evanescent field. We found that this NSOM system strongly reduces the background of the dye fluorescence and allows for the measurement of the fluorescence intensity below the diffraction limit of the excitation source.

Near-field optical microscope with a multiheight scanning imaging mode.

A near-field scanning optical microscope has been developed to yield optical images with various gap distances between the probe and the sample surface. The microscope uses an apertureless metallic probe, the position of which is controlled by regulation of the tunneling-electron current from the probe to the sample and by computer-generated bias voltage. Experimental results of near-field optical imaging with the developed microscope at different gap distances are shown. Thirteen images at gap distances of 0 to 500nm demonstrate that the near-field image depends strongly on the gap distance. The imaging characteristics of a near-field imaging system are shown with the spatial-frequency spectra of images. Future investigation of the developed microscope is also discussed.

Gold-bead scanning near-field optical microscope with laser-force position control.

We have developed a scanning near-field optical microscope with an optically trapped metallic particle that has a small diameter compared to the wavelength of visible light. In this microscope we employed spot illumination to enhance the intensity of light scattered from a probe particle so we could reduce the diameter of the probe particle to 40 nm. We detected slight irregularities of the surface of the cover glass near 10-nm depth. Also, we observed gold colloidal particles on the surface of the cover glass.

Changes in monoclonal antibody productivity of recombinant BHK cells immobilized in collagen gel particles.

Animal cell perfusion high density culture is often adopted for the production of biologicals in industry. In high density culture sometimes the productivity of biologicals has been found to be enhanced. Especially in immobilized animal cell culture, significant increase in the productivity has been reported. We have found that the specific monoclonal antibody (MAb) productivity of an immobilized hybridoma cell is enhanced more than double. Several examples of enhancing productivities have been also shown by collagen immobilized cells. Immobilized cells involve some different points from non-immobilized cells in high density culture: In immobilized culture, some cells are contacted together, resulting in locally much higher cell concentration more than 10(8) cells/ml. Information originating from a cell can be easily transduced to the others in immobilized culture because the distance between cells is much nearer. Here we have performed collagen gel immobilized culture of recombinant BHK cells which produce a human IgG monoclonal antibody in a protein-free medium for more than three months. In this high density culture a stabilized monoclonal antibody production was found with around 8 times higher specific monoclonal antibody productivity compared with that in a batch serum containing culture. No higher MAb productivity was observed using a conditioned medium which was obtained from the high density culture, indicating that no components secreted from the immobilized cells work for enhancing monoclonal antibody production. The MAb productivity by the non-immobilized cells obtained by dissolving collagen using a collagenase gradually decreased and returned to the original level in the batch culture using a fresh medium. This suggests that the direct contact of the cells or a very close distance between the cells has something to do with the enhancement of the MAb productivity, and the higher productivity is kept for a while in each cell after they are drawn apart.

Differential contribution of metal complexation and dimerization to the chemotherapeutic potential of bicyclen-Zn2II complex against human immunodeficiency virus.

1,1'-(m-Xylenediyl)-bis(1,4,7,10-tetraazacyclododecane)-Z n2II complex (m-xylenediyl-bicyclin-Zn2II), a potent inhibitor of human immunodeficiency virus (HIV), was obtained from cyclin by a combination of dimerization and metal complexation. The ratio of median cytotoxic concentration against host cells (CC50) and median effective concentration against HIV cytopathogenicity (EC50), referred to as the selectivity index (SI), was regarded to be a measure of anti-HIV activity. These two chemical modifications contributed to a potent, in vitro anti-HIV activity of m-xylenediyl-bicyclin-Zn2II by respectively increasing the CC50 and decreasing the EC50 in comparison with those of cyclin.

Improved production of phenomycin by a genetically engineered Escherichia coli.

We established an improved production of an antitumor polypeptide anti biotic, phenomycin (PHM), by using a genetically engineered Escherichia coli. Phenomycin consists of 89 natural amino acids without intramolecular disulfide bridge. PHM gene was synthesized as a fusion gene in which PHM at the C-terminus and the residues 1 approximately 20 of Hirudin variant 1 (HV1) at the N-terminus connected by a factor Xa recognition sequence (Ile-Glu-Gly-Arg). E coli JM 109 transformed with a plasmid containing the synthesized gene expressed a fusion protein and the trypsinization of the fusion protein purified by ultrafiltration and ion-exchange chromatography gave efficiently recombinant PHM at a final yield of 50 mg/liter of culture. This PHM yield was six times higher than that obtained by a natural PHM producing strain of Streptoverticillium baldacci. Recombinant PHM was not distinguishable from natural PHM in all aspects observed.

Structures of nine oxygenated 4-methylene sterols from Hachijo marine sponge Theonella swinhoei.

Nine new sterols have been isolated from a marine sponge, Theonella swinhoei. Of these, seven sterols were found to be conicasterol derivatives [(24R)-4-methylene-24-methyl-8(14)-cholesten-3 beta-ol] oxygenated at carbon-7 and/or carbon-15. The other two were (24R)-7 beta,8 beta-epoxy-14 alpha-methoxy-4-methylene-24-methylcholestan- 3 beta-ol and (24R)-8,14-seco-8,14-dioxo-4-methylene-24-methylcholestan-3 beta-ol.

Reversal of daunomycin and vinblastine resistance in multidrug-resistant P388 leukemia in vitro through enhanced cytotoxicity by triterpenoids.

Examined in vitro were the effects of some triterpenoids from Panax (Araliaceae) and Glycyrrhiza (Leguminosae) spp. on the sensitivity to daunomycin (DAU) and vinblastine (VBL) of adriamycin (ADM)-resistant P388 leukemia cells (P388/ADM), which were resistant to multiple anticancer drugs. Quasipanaxatriol, 20(S)-protopanaxatriol, ginsenoside Rh2, and compound K greatly enhanced the cytotoxicity of the anti-cancer drugs in P388/ADM cells. The extent of enhancement was different among the triterpene compounds; the 4- to 46-fold increase in DAU cytotoxicity was observed in P388/ADM cells in the presence of non-toxic or marginally toxic concentrations of individual compounds, while those for VBL were in the ratios of 2- to 37-fold. The maximum increase in cytotoxicity was observed with 50 microM quasipanaxatriol; the resistance indices defined to be the ratios of the IC50 values for P388/ADM and P388 parental cells decreased from 79 to 1.7 and from 180 to 4.9 in the cases of DAU and VBL, respectively. The reversal of DAU resistance in P388/ADM by quasipanaxatriol could be explained by the effective accumulation of the drugs mediated by the DAU-efflux blockage.

Structure-activity correlationship and strain specificity of polyoxometalates in anti-human immunodeficiency virus activity.

The anti-human immunodeficiency virus (HIV) activity of polyoxometalates of representative structural families, such as Keggin, lacunary Keggin, trivacant Keggin, Keggin sandwich, Wells-Dawson and Wells-Dawson sandwich, was determined using two strains of HIV type 1 (HIV-1HTLV-IIIB and HIV-1SF-2H). The compounds were preferably selected to cover both polyoxotungstates and polyoxomolybdates in each structural family. In general, polyoxotungstates of Keggin, lacunary Keggin, trivacant Keggin, Keggin sandwich, Wells-Dawson and Wells-Dawson sandwich structures showed anti-HIV-1HTLVIIIB activity, whereas most compounds not included in these structural categories were inactive. Among the compounds with a potent anti-HIV-1HTLV-IIIB activity, those of Keggin and its closely related structural families (lacunary Keggin, trivacant Keggin and Keggin sandwich) inhibited the cytopathogenicity and syncytium formation caused by HIV-1SF-2 to a much higher extent compared with HIV-1HTLV-IIIB-related ones. The difference between the spectra of anti-HIV-1HTLV-IIIB activity and the specificity for HIV-1SF-2H might result from differential structural requirements in these functions.

Novel assay system favorable for the study of cell-to-cell transmission of HIV-1 and its application to the evaluation of anti-HIV drugs.

The cell-to-cell transmission of human immunodeficiency virus type 1 (HIV-1) was studied using MOLT-4 cells chronically infected with a variant strain of HIV-1SF-2 (MOLT-4/HIV-1SF-2H) and CD4+ human lymphoid MT-4 cells. MOLT-4/HIV-1SF-2H cells produced less than 1 TCID50 infectious particles per day as determined by the cytopathogenicity in MT-4 cells. However, the expression of envelope glycoproteins gp120 and gp41 on the MOLT-4/HIV-1SF-2H cell membrane was satisfactory for syncytium formation with the uninfected MOLT-4 cells. When MOLT-4/HIV-1SF-2H and MT-4 cells were co-cultured, severe cytopathogenicity was observed in MT-4 cells without being accompanied by the formation of multi-nucleated cells. Thus, the system consisting of MOLT-4/HIV-1SF-2H and MT-4 cells is convenient for exclusive study of the mechanism of cell-to-cell transmission of HIV-1. Using various compounds, it was confirmed that cell-to-cell transmission required both gp120/gp41-CD4 binding and de novo DNA synthesis.