PubMed Health⌕ Search

Biomedical subjects

Y Kobuke

Publications and source records attributed to Y Kobuke.

9 recordsLinked to original sources
PubMed2004

LAS in urban rivers and factors contributing to reduction of their concentrations.

LC/MS analysis with improved SPE preparation was applied to determine trace amounts of LAS in river waters. By using this procedure, the distribution of LAS was investigated and compared with the previous concentration level measured by HPLC in the Akashi River flowing through urbanized coastal areas in Hyogo Prefecture, western Japan. Detected LAS were in the range of 0.6-11 microg/L and considerably lower than those in 1985. This indicated that LAS concentration levels reduced to 1/10 and below during the past 18 years. From the model analysis, major factors contributing to the reduction of their concentrations were estimated to be the sewerage development and the decrease of consumption of anionic surfactants. Statistical analysis of MBAS monitoring data suggested that over 90% of sewerage diffusion rate was needed in order to reduce LAS to the concentration level of the order of 10 microg/L in river waters.

Alkanesulfonic Acids↗
PubMed2002

Environmental risk evaluation for anionic surfactants based on the characteristics of appearance of high concentration in rivers.

Environmental risk evaluation for anionic surfactants based on the characteristics of the appearance of a high concentration was developed together with statistical analysis of MBAS data in rivers of Hyogo Pref., western Japan. Annual average MBAS at different monitoring points generally decreased during past 10 years and their geometric mean reduced by 70%. This rate of decrease agreed well with that of estimated environmental loads of anionic surfactants in the study area. The proportions of monitoring point with high risk (risk ratio over 1.0) to fish increased in the order of the weakness of toxicity in both 1989 and 1998. Their proportions were 2% for acute toxicity, 17% for chronic toxicity and 66% for avoidance response in 1989, which surpassed the proportion evaluated using average concentration in all cases. The proportions for whole toxicities decreased in 1998, however, the proportion for avoidance response kept considerably high level (42%). These results indicated the usefulness of environmental risk evaluation for surfactants based on the characteristics of appearance of high concentration, and also suggested the need for field investigation for fish avoidance response.

Animals↗
PubMed2001

Synthesis of bipyridylene-bridged bisporphyrin by nickel-mediated coupling reaction: ON-OFF control of cofacial porphyrin unit by reversible complexation.

Novel bipyridylene-bridged bisporphyrin 1a, in which two porphyrin units were attached directly to symmetrical 4,4'-positions of the 2,2'-bipyridyl group, was synthesized by a nickel(0)-mediated homocoupling reaction of 5,10,15-tris(n-heptyl)-20-(2'-bromo-4'-pyridyl)porphyrinatozinc (3a) in 58% yield. Spatial geometries of two porphyrins in 1a were regulated by reversible complexation of the bipyridyl part with PdCl(2). Thus, the addition of 2.2 equiv of palladium chloride to 1a converted the freely rotating conformation to the cofacial bisporphyrin 2a. The subsequent addition of 4,4'-dimethyl-2,2'-bipyridine 9 regenerated the initial bisporphyrin 1a.

Journal Article↗
PubMed2001

Artificial ion channels showing rectified current behavior.

Voltage-dependent artificial ion channels 3 and 4 were synthesized. Two cholic acid derivatives were connected through a m-xylylene dicarbamate unit at 3-hydroxyl groups. Asymmetries were introduced by terminal hydrophilic groups, carboxylic acid and phosphoric acid for 3 and hydroxyl and carboxylic acid for 4. Under basic conditions, these headgroups in 3 and 4 are expected to be dissociate into -1/-2 (pH 8.2) and 0/-1 (pH 7.2), respectively. Single ion channel properties were examined by a planar bilayer lipid membrane method under symmetrical 500 mM KCl at pH 8.2 or 7.2. When 3 and 4 were introduced into the bilayer membrane under application of positive voltage (a positive-shift method), the current values at positive applied voltage were larger than the corresponding ones at the negative applied voltage. The current-voltage plots were fitted by curves through a zero point to show clear rectification properties. The direction of rectification could be controlled by positive- or negative-shift methods. Vectorial alignment of terminal headgroup charges by the voltage-shift incorporation is essential for giving voltage-dependent rectified ion channels.

Carbamates↗
PubMed2001

Transmembrane ion channels constructed of cholic acid derivatives.

A new class of supramolecular transmembrane ion channels was prepared by linking two amphiphilic cholic acid methyl ethers through biscarbamate bonds to afford bis(7,12-dimethyl-24-carboxy-3-cholanyl)-N,N'-xylylene dicarbamate 2 and bis[7,12-dimethyl-24-(N,N,N-trimethylethanaminium-2-carboxylate)-3-cholanyl]-N,N'-xylylene dicarbamate dichloride 3. When incorporated into a planar bilayer membrane, both compounds showed stable (lasting 10 ms to 10 s) single ion channel currents. Only limited numbers of relatively small conductances were characterized for these channels (5-20 pS for 2 and 5-10 pS for 3, 10 and 17 pS for 2, and 9 pS for 3 in particular). Both channels were cation selective, and permeability ratios of potassium cation to chloride anion were 17 and 7.9 for 2 and 3, respectively, reflecting the difference in ionic species of the headgroup. Both channels 2 and 3 showed significant potassium selectivity over sodium by a factor of 3.1 and 3.2, respectively. No Li(+) currents were observed for 2, showing sharp discrimination between Na(+) or K(+).

Carboxylic Acids↗
PubMed1996

[Artificial models of transport proteins in membrane].

Artificial molecules were designed to mimic membrane transport proteins which produce large and selective ion fluxes across biological membrane with functions of flux-control. Several amphiphilic lipid molecules were assembled in bilayer lipids to make supramolecular ion channels which gave single ion channel currents across planar lipid bilayers. Stable and constant conductance levels were observed with transitions between open and closed states. Unimolecular channels were also designed by using macrocyclic resorcinol tetramer, calix [6] arene or cyclodextrin. These unimolecular channels gave a single conductance and a sharp ion selectivity. All these channels were cation selective over anion. Ionic currents was successfully modulated by the application of membrane potential or photochemical isomerization.

Carrier Proteins↗
PubMed1982

Specific recognition of pyrophosphate in nucleotides.

The lipophilic diammonium cation 1 was demonstrated to be a reagent to discriminate the number of the phosphate in nucleotides. Thus the highly hydrophilic nucleotides were selectively extracted into an organic phase by the formation of ion-pairs and selectively transported through a membrane by a carrier mechanism. The compound was also shown to be an efficient phase transfer reagent which activated the phosphate anion of AMP to give a facile synthesis of pyrophosphate linkages, ADP and ATP, without any protection of the sugar moiety.

Adenine Nucleotides↗
PubMed1979

Molecular recognition of nucleotides by means of ionic interaction in hydrophobic media.

Adenosine phosphates, AMP, ADP and ATP were found to be recognized and extracted from aqueous to an organic phase by the newly prepared lipophilic diammonium salt, N,N'-distearyldiammonium dichloride of 1,4-diazabicyclo [2.2.2] octane 1. ADP and ATP were specifically bound by 1 under the condition of no appreciable binding of AMP. The conventional phase transfer reagent, trioctylmethylammonium chloride 2 was far less effective and lacked selectivity fort the binding of adenosine phosphates. This diammonium salt was used as a specific carrier of ADP in the passive transport through a liquid membrane. A high selectivity was observed in the transport rate of ADP relative to that of AMP.

Adenosine Diphosphate↗