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Biomedical subjects

Kunimitsu Kaya

Publications and source records attributed to Kunimitsu Kaya.

At least 19 recordsLinked to original sources
PubMed2006

Solvent effects in the preparation of molecularly imprinted polymers for melatonin using N-propionyl-5-methoxytryptamine as the pseudo template.

To clarify the role of diluents in the preparation of molecularly imprinted polymers utilizing only hydrogen bonding, we investigated the effects of diluents by using different solvents. Melatonin (N-acetyl-5-methoxytryptamine), an amide bond and indole ring-containing hormone was chosen as the target molecule. N-Propionyl-5-methoxytryptamine was used as the pseudo template, methacrylic acid as the functional monomer, and solvents were used as diluents. Interactions between the template, the functional monomer, melatonin, and the solvents, were observed by 1H NMR spectroscopy. The polymers were evaluated by high-performance liquid chromatography. The results suggest the hydrogen bonding-acceptor capacity of the solvent is the most important factor in the preparation of molecularly imprinted polymers for hydrogen bonding-donating molecules. Hydrogen bonding between the template, the functional monomer, and solvent can be estimated from the chemical shifts in 1H NMR spectra of those molecules in the solvent.

5-Methoxytryptamine↗
PubMed2006

Fully automated liquid chromatography-mass spectrometry determination of 17beta-estradiol in river water.

Surface modified molecularly imprinted polymers (SM-MIPs) for 17beta-estradiol (E2), utilizing 6-ketoecradiol as a pseudo template were prepared. MIPs for E2 were synthesized using 4-vinyl pyridine and ethylene dimethacrylate as a functional monomer and cross-linking agent, respectively. MIPs selectively retained E2 and provided excellent chromatographic resolution from interfering compounds inherent in river water sample matrices. Therefore, freshly prepared MIPs were applied to quantitative mass spectrometric (negative electrospray ionization mode) detection of low levels of E2 in river water sample. In order to pre-concentrate the target compound for HPLC analysis, column switching was coupled with a pretreatment column packed with the MIPs. The repeatability of actual determinations of river water sample, in which background E2 was not detected, spiked with 50 ng/L of E2 was 2.2% RSD with a detection limit and qualification limit of 1.8 and 5.4 ng/L, respectively. Surface modification of MIP particlefs packed in the pretreatment column provided selective affinity and on-line concentration of low levels of E2 while simultaneously eliminating sample matrix interference, resulting in a significant increase in sensitivity and reproducibility for liquid chromatography-mass spectrometry analysis of E2 in river water sample.

Chromatography, High Pressure Liquid↗
PubMed2006

Trungapeptins A-C, cyclodepsipeptides from the marine cyanobacterium Lyngbya majuscula.

Trungapeptins A-C (1-3) were isolated from the marine cyanobacterium Lyngbya majuscula collected from Trung Province, Thailand. Their gross structures were elucidated by interpretation of spectroscopic data. The absolute configurations of the amino acids and phenyllactic acid were determined by Marfey's and chiral HPLC analyses, respectively. The relative stereochemistry of 3-hydroxy-2-methyl-7-octynoic acid (Hmoya) of trungapeptin A was elucidated by application of the J-based configuration analysis, and its absolute stereochemistry was established to be 2S, 3R by Mosher's method. The structures of compounds 1-3 are closely related to the antanapeptins, a series of depsipeptides isolated from a Madagascan collection of L. majuscula.

Animals↗
PubMed2005

Preparation of a novel molecularly imprinted polymer using a water-soluble crosslinking agent.

A molecularly imprinted polymer was prepared using a water-soluble crosslinking agent. An ionic complex was utilized as the assembly for the template molecule and the functional monomer, and water as porogenic solvent during preparation of the imprinted polymer. The results of chromatographic evaluations for the prepared polymer suggested that the polymer had much lower hydrophobicity compared with usual octadecyl group bonded silica or the usual molecular imprinted polymer prepared from ethyleneglycol dimethacrylate, and the selective recognition ability for template molecule in the completely aqueous condition.

Journal Article↗
PubMed2005

Selective control of toxic Microcystis water blooms using lysine and malonic acid: an enclosure experiment.

Three enclosures (10 x 10 x 1.5-1.3 m in depth) were set beside Dianch Lake, Kunming, People's Republic of China, for the period from July 28 to August 26, 2002. The enclosures were filled with cyanobacterial (Microcystis aeruginosa) water bloom-containing lake water. Lake sediment that contained macrophytes and water chestnut seeds was spread over the entire bottom of each enclosure. Initially, 10 g/m(2) of lysine was sprayed in Enclosure B, and 10 g/m(2) each of lysine and malonic acid were sprayed together in Enclosure C. Enclosure A remained untreated and was used as a control. The concentrations of lysine, malonic acid, chlorophyll a, and microcystin as well as the cell numbers of phytoplankton such as cyanobacteria, diatom, and euglena were monitored. On day 1 of the treatment, formation of cyanobacterial blooms almost ceased in Enclosures B and C, although Microcystis cells in the control still formed blooms. On day 7 Microcystis cells in Enclosure B that had been treated with lysine started growing again, whereas growth was not observed in Microcystis cells in Enclosure C, which had been treated with lysine and malonic acid. On day 28 the surface of Enclosure B was covered with water chestnut (Trapa spp.) and the Microcystis blooms again increased. In contrast, growth of macrophytes (Myriophllum spicatum and Potamogeton crispus) was observed in Enclosure C; however, no cyanobacterial blooms were observed. Lysine and malonic acid had completely decomposed. The microcystin concentration on day 28 decreased to 25% of the initial value, and the pH shifted from the initial value of 9.2 to 7.8. We concluded that combined treatment with lysine and malonic acid selectively controlled toxic Microcystis water blooms and induced the growth of macrophytes.

China↗
PubMed2005

Leucine aminopeptidase M inhibitors, cyanostatin A and B, isolated from cyanobacterial water blooms in Scotland.

Two leucine aminopeptidase M inhibitors, cyanostatin A and B, were isolated from cyanobacterial water blooms at Loch Rescobie in Scotland, and specifically from a Microcystis species. Both inhibitors were lipopeptides containing 3-amino-2-hydroxydecanoic acid and weak inhibitors of protein phosphatase (PP2A). Both strongly inhibited the activity of leucine aminopeptidase M with IC50 values of 40 and 12 ng/ml, respectively.

Anabaena↗
PubMed2005

A new simply and effective fractionation method for cylindrospermopsin analyses.

A new simply and effective fractionation method for cylindrospermopsin (CYN) analyses was developed. The extract from cells of Cylindrospermopsis raciborskii was resuspended with 0.1 M carbonate buffer at pH 10.5, and pass through the double-cartridges column which was consisted of a styrene polymer cartridge and an anion exchange cartridge. CYN and deoxy-CYN were adsorbed with the anion exchange cartridge. After separation of the anion exchange cartridge, adsorbed compounds were eluted from the cartridge with 50% methanol containing 1% formic acid solution. CYN and deoxy-CYN were selectively condensed in the eluted solution. When CYN was analyzed by LC-photodiode array or LC/MS, only two peaks of CYN and deoxy-CYN were detected quantitatively. The results suggest that the fractionation method is a useful method for CYN analyses and must be utilized for CYN purification.

Alkaloids↗
PubMed2005

Two new chymotrypsin inhibitors isolated from the Cyanobacterium Microcystis aeruginosa NIES-88.

Micropeptins 88-N (1) and 88-Y (2), new 3-amino-6-hydroxy-2-piperidone (Ahp)-containing cyclic depsipeptides, were isolated from Microcystis aeruginosa NIES-88. The structures were elucidated by analyses of HRFABMS, 1D and 2D NMR spectra, and chemical degradation. Micropeptins 88-N and 88-Y inhibited chymotrypsin. The inhibitory activities were closely related to the amino acid residue that was attached to the amino group of Ahp.

Amino Acids↗
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

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

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

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

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

Evidence for recombination in the microcystin synthetase (mcy) genes of toxic cyanobacteria Microcystis spp.

Recombination has been suggested to be an important factor for the genetic variation of bacterial genes, but few studies have dealt with intragenic recombination between the same or closely related species of cyanobacteria. Here we provide strong evidence for recombination in the microcystin synthetase (mcy) gene cluster of the toxic cyanobacteria Microcystis spp. This gene cluster contains 10 genes (mcyA to J) that encode a mixed polyketide synthase (PKS)/nonribosomal peptide synthetase (NRPS) complex. mcy gene sequences were determined for four selected regions (within mcyA, D, G, and J) within the mcy gene cluster from 1 Canadian and 10 Asian toxic Microcystis and compared with previously published mcy sequences. Split decomposition analysis indicated a reticulate phylogeny of mcyA, and several potential recombination tracts of mcyA were identified by the RDP analysis and a runs test implemented in GENECONV. In contrast, no recombination was detected in the mcyD, G, and J sequences. However, discrepancies among the four mcy gene genealogies were evident from the results of independent split decomposition analyses, which were further supported by incongruence length difference (ILD) tests. Taken together, these findings suggest that both intragenic and intergenic recombination within the mcy gene cluster contributes to the genetic diversity of the mcy genes of Microcystis spp.

Bacterial Proteins↗
PubMed2004

Toxicity recognition of hepatotoxin, homologues of microcystin with artificial trapping devices.

A hepatotoxin produced by cyanobacteria, microcystin (MC), was chromatographically discriminated with newly prepared artificial trapping devices. MC involves up to 70 kinds of homologues, and because homologues have similar toxicity, effective removal and analysis methods have been required. As a trapping device to discriminate MC, we have developed a novel technique for preparation of the "imprinted recognition site" into the crosslinked nano-scale structure, namely "Fragment Imprinting Effect." This technique is simple, and its possible application fields are relatively broad. We have demonstrated the recognition for MC homologues through the combination of two different artificial molecular recognition devices prepared through fragment imprinting technique.

Carcinogens↗
PubMed2003

On-column concentration of bisphenol A with one-step removal of humic acids in water.

An efficient extraction method for bisphenol A from environmental water including contaminants was developed using surface selective localization of functional group, on a polymeric separation device. The polymer utilized in this study was prepared through a kind of molecular imprinting technique, namely fragment imprinting effect utilizing a pseudo-template molecule (p-tert.-butylphenol) instead of bisphenol A. The concentration of bisphenol A onto the polymer device prepared, up to 1000 times concentration from environmental water including contaminants (humic acids), was achieved very easily with interesting exclusion effect for humic acids. The results obtained in this study suggest that molecular imprinting with the pseudo-template molecule is quite an effective way for selective concentration of the diluted target molecule from other contaminants including similar functional group with the target molecule.

Benzhydryl Compounds↗