Biomedical subjects

Nobuo Tanaka

Publications and source records attributed to Nobuo Tanaka.

At least 55 records · Page 3Linked to original sources

PubMed2005

Acoustic cluster control of noise radiated from a planar structure.

Acoustic cluster control is proposed for the purpose of achieving global sound attenuation of a planar structure. First, acoustic cluster filtering using a point sensor array is presented, which enables the grouping of sound radiated from a target object into a set of clusters, such that each cluster possesses the same common characteristics. This allows the possibility of extracting the cluster of interest without causing observation spillover. Based on the principle of reciprocity, cluster actuation using a point source array is then presented. Driving the source array in accordance with a proposed control law, the excitation of the designated cluster is performed without causing control spillover. Moreover, by combining both acoustic cluster filtering and acoustic cluster actuation, acoustic cluster control may be performed. In implementing acoustic cluster control, the necessary and sufficient condition for the acoustic cluster control is illustrated. It is also shown that the sound radiated from a planar structure may be captured in appropriate acoustic cluster filtering so that acoustic cluster control may be implemented. Experiment was conducted demonstrating the capability as well as the validity of the acoustic cluster filtering, actuation, and control for suppressing the noise radiated from a rectangular panel.

Journal Article↗

PubMed2005

A norovirus protease structure provides insights into active and substrate binding site integrity.

Norovirus 3C-like proteases are crucial to proteolytic processing of norovirus polyproteins. We determined the crystal structure of the 3C-like protease from Chiba virus, a norovirus, at 2.8-A resolution. An active site including Cys139 and His30 is present, as is a hydrogen bond network that stabilizes the active site conformation. In the oxyanion hole backbone, a structural difference was observed probably upon substrate binding. A peptide substrate/enzyme model shows that several interactions between the two components are critical for substrate binding and that the S1 and S2 sites appropriately accommodate the substrate P1 and P2 residues, respectively. Knowledge of the structure and a previous mutagenesis study allow us to correlate proteolysis and structure.

3C Viral Proteases↗

PubMed2005

Plasma leptin levels of elite endurance runners after heavy endurance training.

A decrease in testosterone levels and an increase in cortisol levels are observed in male athletes with the overtraining syndrome (OTS). Cortisol causes blood leptin levels to rise and testosterone has an inverse relationship with blood leptin levels. Therefore, we hypothesized that the hormonal changes as a result of OTS induce an increase in leptin. To test this hypothesis, we examined the relationship among changes in leptin, testosterone and cortisol in thirteen male collegiate distance runners (aged 20.3+/-1.1 years) before and after an 8-day strenuous training camp. Runners ran 284.1+/-48.2 km during the training camp. Body fat percentages and plasma glucose concentrations decreased significantly after the training. Non-ester fatty acids and total cholesterol concentrations in blood were unchanged. Serum cortisol concentrations showed a significant increase after the training camp (from 11.82+/-2.00 microg/dl to 16.78+/-3.99 microg/dl), and serum testosterone decreased significantly (from 408.0+/-127.6 ng/dl to 265.2+/-97.6 ng/dl). The ratio of testosterone to cortisol (TCR) dropped by 50% after training (from 35.62+/-13.69 to 16.94+/-8.47). These results suggest that the subjects reached a state of the OTS. Contrary to our hypothesis, plasma leptin was not significantly changed (from 1.34+/-0.29 ng/ml to 1.49+/-0.18 ng/ml). Delta Plasma leptin was not significantly correlated with delta serum cortisol, delta TCR or delta fat percentage. However, delta serum testosterone was positively correlated with delta plasma leptin (r=596, p<0.05). Plasma leptin concentrations might modulate the secretion of testosterone in overtraining conditions. In conclusion, the change in blood leptin level is independent of the changes in cortisol, TCR and fat percentage in highly trained male athletes in the state of the OTS.

Adult↗

PubMed2004

A molecular recognition strategy towards tetra-chlorinated dibenzo-p-dioxins, TCDDs.

Uniformly sized polymeric separation media were prepared using o- or p-xylene as porogenic template to investigate chromatographic selectivity towards tetra-chlorinated dibenzo-p-dioxins (TCDDs). TCDDs having chlorine atoms at ortho positions of phenyl rings were selectively retained on stationary phase prepared with o-xylene as porogenic template, while TCDDs having chlorine atoms at para positions of phenyl ring were found to be retained selectively on the stationary phase imprinted by the porogenic template, p-xylene. Slightly longer cross-linking agent afforded chromatographically selective retention for larger TCDD isomers. It was also found that positional relationship between substituted chlorine atoms was also important for chromatographic recognition.

Chromatography, High Pressure Liquid↗

PubMed2004

Crystallization and preliminary X-ray studies on the reaction center-light-harvesting 1 core complex from Rhodopseudomonas viridis.

The reaction center-light-harvesting 1 (RC-LH1) core complex is the photosynthetic apparatus in the membrane of the purple photosynthetic bacterium Rhodopseudomonas viridis. The RC is surrounded by an LH1 complex that is constituted of oligomers of three types of apoproteins (alpha, beta and gamma chains) with associated bacteriochlorophyll bs and carotenoid. It has been crystallized by the sitting-drop vapour-diffusion method. A promising crystal diffracted to beyond 8.0 A resolution. It belonged to space group P1, with unit-cell parameters a = 141.4, b = 136.9, c = 185.3 A, alpha = 104.6, beta = 94.0, gamma = 110.7 degrees. A Patterson function calculated using data between 15.0 and 8.0 A resolution suggested that the LH1 complex is distributed with quasi-16-fold rotational symmetry around the RC.

Bacterial Proteins↗

PubMed2004

Capillary liquid chromatographic determination of cellular flavins.

A capillary LC system was set up and optimized, in which a UV absorbance detector was used and a monolithic silica-ODS column as the separation column. Two on-line concentration techniques, namely, gradient elution mode and in-tube solid-phase ion-pair microextraction (SPIPME), were combined with the capillary LC system, which proved to be beneficial to enhance the concentration sensitivity by enabling the injection of large volumes of samples. The limits of detection at ppb levels for the flavins [riboflavin, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD)] were achieved using the two techniques. For in-tube SPIPME, a monolithic silica-ODS column was employed as the extraction column, on which FAD and FMN were retained b y interaction with an ion-pair reagent, tetrabutylammonium phosphate, resulting in greater than 110-fold enhancement in their concentration sensitivities relative to conventional injection method. The reproducibility and linearity of the two methods were investigated. The two methods were applied to analyze trace amounts of flavins in bacterial Escherichia coli cell extracts and recombinant flavoenzymes.

Chromatography, Liquid↗

PubMed2004

Crystallization and preliminary X-ray crystallographic analysis of chitinase F1 (ChiF1) from the alkaliphilic Nocardiopsis sp. strain F96.

Chitinase F1 (ChiF1) isolated from the alkaliphilic Nocardiopsis sp. strain F96 is a family 18 chitinase that hydrolyzes chitin, an insoluble beta-1,4-linked polymer of N-acetylglucosamine. Crystals of recombinant ChiF1 with molecular weight of 33 000 Da were grown to a suitable size for X-ray structure analysis using 18%(w/v) polyethylene glycol 8000, 200 mM zinc acetate dehydrate and 100 mM sodium cacodylate buffer pH 6.5. Diffraction data were collected at SPring-8 and show that the crystals belong to the trigonal space group P3(1)12 or P3(2)12, with unit-cell parameters a = 56.0, c = 179.5 A, and diffract X-rays beyond 1.2 A resolution. Crystallographic analysis was carried out using the multiwavelength anomalous diffraction (MAD) method using zinc as the anomalous scatter. The binding of Zn atoms was clarified from the Bijvoet and dispersive Patterson functions, which gave prominent zinc-zinc self-vectors on the Harker section.

Actinomycetales↗

PubMed2004

Photophysical properties of a carbazolyl mesogen of 8PCzC as revealed by absorption, fluorescence, and transient absorption measurements.

Fluorescence spectra in three phases [crystalline, smectic A liquid crystal (SmA), and isotropic] of a mesogen including one carbazolyl (Cz) chromophore, 4'-n-octylphenyl carbazole-2-carboxylate (8PCzC), were measured at various temperatures and compared with fluorescence spectra in solvents with various dielectric constants. Further, for the first time, picosecond transient absorption spectroscopy was applied to elucidating photoinduced electron-transfer dynamics (charge separation, charge recombination, and hole transfer reactions) in the three phases of 8PCzC doped with a small amount of an electron acceptor. The fluorescence spectra showed clearly the presence of two crystalline phases, which was supported by DSC measurement. On the basis of a comparison of the fluorescence spectra and those in solution, the 8PCzC molecule in the first crystal structure was suggested to be in polar environment compared to that in the second one. The fluorescence yields of 8PCzC in both SmA and isotropic phases were remarkably small compared to that in crystalline one. This was ascribed to the formation of hydrogen bonds between 8PCzC molecules in both SmA and isotropic phases. As a first approximation, the picosecond transient absorption spectra in the three phases of 8PCzC doped with 2,4,7-trinitrofluorenone were analyzed by the simple model of one-dimensional hole migration. The rate constants obtained for the hole transfer from the cation state of Cz chromophore to neighboring Czs decreased in the order of SmA (approximately 10(9) s(-1)) > isotropic (approximately 10(8) s(-1)) > crystalline (approximately 10(7) s(-1)) phases, although these measurement temperatures were different.

Absorption↗

PubMed2004

Chromatographic molecular recognition for catechol-related compounds using thiacalix[4]arene as an effective selector.

Thiacalix[4]arene (5,11,17,23-tetra- tert-butyl-25,26,27,28-tetrahydroxy-2,8,14,20-tetrathiacalix[4]arene) is an amphiphilic molecule comprising four p-tert-butylphenol-like groups ortho-linked by single sulfur atoms. This molecule has a high electron density area owing to the close proximity of the hydroxyl groups and sulfur atoms. We studied the applicability of this interesting compound as a selector for high-performance liquid chromatography (HPLC) thereby presumably exploiting this feature. Firstly, uniformly sized polymer particles were prepared by using a multi-step swelling and polymerization method with ethylene glycol dimethacrylate (EDMA) as a cross-linker. Methacrylic acid (MAA) was introduced onto the surface of the resulting polymer particles through a new modification method. Thiacalix[4]arene was chemically bonded through the MAA group by using 1,4-dibromobutane as a spacer to reduce steric hindrance around the MAA and the polymer particle itself. The performance of the prepared polymer-based thiacalix[4]arene-modified stationary phase was evaluated with HPLC. Specific chromatographic retention behavior was observed for catechol relative to positional isomers of xylene, cresol, and benzene-diol. Catecholamine and catechol showed specific chromatographic retention behavior.

Catecholamines↗

PubMed2004

Crystallization and preliminary X-ray diffraction studies of the hyperthermophilic archaeal sulredoxin having the unique Rieske [2Fe-2S] cluster environment.

The hyperthermophilic archaeal sulredoxin from Sulfolobus tokodaii is a water-soluble high-potential Rieske [2Fe-2S] protein with unique pH-dependent redox properties compared with its mesophilic homologues in cytochrome bc1/b6f complexes. The oxidized recombinant sulredoxin has been crystallized by the hanging-drop vapour-diffusion method using 30%(v/v) polyethylene glycol 400, 0.1 M cadmium chloride and 0.1 M sodium acetate pH 4.6. The crystals diffracted to beyond 2.0 A resolution and belong to the cubic space group F4(1)32, with unit-cell parameter a = 163.00 +/- 0.05 A. The asymmetric unit contains one sulredoxin molecule. Three-wavelength MAD data were collected.

Archaeal Proteins↗

PubMed2004

Interval immobilization technique for recognition toward a highly hydrophilic cyanobacterium toxin.

A novel adsorption medium containing selective molecular recognition site for one of the powerful cyanobacterium toxins, Cylindrospermopsin (CYN) was developed using a special technique, namely interval immobilization technique. The adsorption medium was prepared using molecular assembly derived from an alternative-template molecule coupled with functional monomers for fixing the interval between the ionic functional groups in CYN. As results of liquid chromatographic evaluations, selective molecular recognition ability for CYN was observed as expected. Further studies proved that the association constant for CYN on this medium was slightly higher than that on blank polymer.

Adsorption↗

PubMed2004

Determination of bisphenol A in environmental water at ultra-low level by high-performance liquid chromatography with an effective on-line pretreatment device.

We have developed a simple HPLC method for the microanalysis of bisphenol A (BPA), which is often contained in environmental water and is known as an endocrine disrupter. HPLC coupled with electrochemical detection requires a simpler procedure of pretreatment compared to GC-MS. In this study, we analyzed BPA using molecularly imprinted polymer as an on-line pretreatment device. This polymer has molecular recognition sites and provides specific selectivity in extraction process. Due to this effect, the detection limit obtained with this HPLC was 0.36 ng/l. This method applied to environmental water and purified water samples containing 2-70 ng/l of BPA successfully. Furthermore, UV detection was performed in some actual analyses.

Benzhydryl Compounds↗

PubMed2004

Structure of bovine carbonic anhydrase II at 1.95 A resolution.

Carbonic anhydrase (CA) is a zinc-containing enzyme that catalyzes the reversible hydration of CO2 to HCO3-. In eukaryotes, the enzyme plays a role in various physiological functions, including interconversion between CO2 and HCO3- in intermediary metabolism, facilitated diffusion of CO2, pH homeostasis and ion transport. The structure of bovine carbonic anhydrase II (BCA II) has been determined by molecular replacement and refined to 1.95 A resolution by simulated-annealing and individual B-factor refinement. The final R factor for the BCA II structure was 19.4%. BCA II has a C-terminal knot structure similar to that observed in human CA II. It contains one zinc ion in the active site coordinated to three histidines and one putative water molecule in a tetrahedral geometry. The structure of BCA II reveals a probable alternative proton-wire pathway that differs from that of HCA II.

Animals↗

PubMed2004

Novel surface-modification techniques for polymer-based separation media. Stimulus-responsive phenomena based on double polymeric selectors.

A pair of polymeric selectors potentially responding to stimulation was introduced onto monosized porous polymer particles to be evaluated as a packing material for HPLC. Possible complexes formed between polyacrylamide (PAAm) and poly(methacrylic acid) (PMAA) were utilized as stimulus responsive polymeric selectors. Uniformly sized base polymer particle was prepared by multi-step swelling and polymerization method, while the introduction of PAAm and PMAA was done by newly invented modification technique. In this technique, a solvent in which both acrylamide (AAm) and methacrylic acid (MAA) monomers are soluble, but PAAm and PMAA are insoluble, was utilized as a modification medium. The polymer particle doubly modified with PAAm and PMAA was utilized as packing material for HPLC and the stimulus responses were evaluated by changing temperature or pH to check change of the slope of a Van't Hoff plot. By using water as a mobile phase, the expected inflection point of the Van't Hoff plot was observed at upper critical solution temperature (UCST) of the polymer complexes and the temperature responsive ability was observed. Moreover, pH responsive ability was studied by using buffer of either pH 4 or 10 as mobile phase. Slope of the plot was changed in buffer of pH 4, but no change of slope was observed in the buffer of pH 10.

Chromatography, High Pressure Liquid↗

PubMed2004

Polymer-based adsorption medium prepared using a fragment imprinting technique for homologues of chlorinated bisphenol A produced in the environment.

A polymer-based adsorption medium having molecular recognition ability for homologues of chlorinated bisphenol A produced in environment was prepared using a fragment imprinting technique. 2,6-Dimethyl phenol was utilized as a pseudo-template molecule and the adsorption media prepared was evaluated by high performance liquid chromatography (HPLC) and solid-phase extraction (SPE). As results, the adsorption medium showed preferable chromatographic retention and specific adsorption ability for the chlorinated bisphenol As having chlorine substituents at 3,5-positions through fragment imprinting effect.

Adsorption↗

PubMed2004

Simple and comprehensive two-dimensional reversed-phase HPLC using monolithic silica columns.

Simple and comprehensive two-dimensional (2D)-HPLC was studied in a reversed-phase mode using monolithic silica columns for second-dimension (2nd-D) separation. Every fraction from the first column, 15 cm long (4.6-mm i.d.), packed with fluoroalkylsilyl-bonded (FR) silica particles, was subjected to the separation in the 2nd-D using one or two octadecylsilylated (C(18)) monolithic silica columns (4.6-mm i.d., 3 cm). Monolithic silica columns in the 2nd-D were eluted at a flow rate of up to 10 mL/min with separation time of 30 s that meets the fractionation every 15-30 s at the first dimension (1st-D) operated at a flow rate of 0.4-0.8 mL/min. Three cases were studied. (1) In the simplest scheme of 2D-HPLC, effluent of the 1st-D was directly loaded into an injector loop of 2nd-D HPLC for 28 s, and 2 s was allowed for injection. (2) Two six-port valves each having a sample loop were used to hold the effluent of the 1st-D alternately for 30 s for one 2nd-D column to effect comprehensive 2D-HPLC without the loss of 1st-D effluent. (3) Two monolithic silica columns were used for 2nd-D by using a switching valve and two sets of 2nd-D chromatographs separating each fraction of the 1st-D effluent with the two 2nd-D columns alternately. In this case, two columns of the same stationary phase (C(18)) or different phases, C(18) and (pentabromobenzyloxy)propylsilyl-bonded (PBB), could be employed at the 2nd-D, although the latter needed two complementary runs. The systems produced peak capacity of approximately 1000 in approximately 60 min in cases 1 and 2 and in approximately 30 min in case 3. The three stationary phases, FR, C(18), and PBB, showed widely different selectivity from each other, making 2D separations possible. The simple and comprehensive 2D-HPLC utilizes the stability and high efficiency at high linear velocities of monolithic silica columns.

Journal Article↗

PubMed2004

Recognition of hepatotoxic homologues of Microcystin using a combination of selective adsorption media.

Microcystin, a hepatotoxin produced by cyanobacteria, was chromatographically discriminated with newly prepared selective adsorption media. Since the name Microcystin refers to up to 70 different homologues, we have developed a novel technique to prepare selective recognition sites, based on the "Fragment Imprinting Effect". The homologues of Microcystin can be individually discriminated from each other by antigen-antibody assay as well as by C18-based HPLC. This is mainly due to differences in the three dimensional structure of Microcystin homologues; however, differences in toxicity are relatively small among the homologues. Therefore we have to measure the total amount of Microcystin homologues present to determine contamination by Microcystins. We have demonstrated the first group recognition for Microcystin homologues through combination of two different selective adsorption media prepared by a fragment imprinting technique.

Bacterial Toxins↗

PubMed2004

High-performance liquid chromatographic enantioseparations on capillary columns containing monolithic silica modified with cellulose tris(3,5-dimethylphenylcarbamate).

Monolithic capillary columns containing native silica gel were modified with cellulose tris(3,5-dimethylphenylcarbamate) (CDMPC) and used for enantioseparations in capillary liquid chromatography. The method adopted for in situ enantioselective modification of monolithic fused silica capillary columns by coating with CDPMC appears to be fairly simple and fast. High efficiency enantioseparations of test racemic compounds and s(everal chiral drugs were achieved in a short time. It was possible to increase the amount of chiral selector present by multiple coating of monoliths with CDMPC. The baseline enantioseparation of 2,2,2-trifluoro-1-(9-anthryl)ethanol was achieved in an analysis time less than 30 s with this capillary column. In addition, reproducible enantioseparations were obtained when the chiral selector was removed from the monolithic column by flushing it with appropriate solvent and the column recoated.

Carbamates↗