Cellulose fiber biodegradation in natural waters: river water,brackish water,and seawater

Cellulose, the main component of plant cell walls, is degradable in nature. However, to the best of our knowledge, this is the first report that compares the biodegradability of cellulose fibers with different structures in natural waters. River water, brackish water, and seawater were collected from the Kamo River and Osaka Bay, Japan. Biodegradation of cellulose fibers with different structures and crystallinities, ramie, mercerized ramie, and regenerated cellulose fibers in the collected natural water was investigated in the dark at 20 °C for 30 days. The primary and aerobic ultimate biodegradability were evaluated by weight loss and biochemical oxygen demand (BOD) tests, respectively. In the weight-loss test, cellulose fibers were found to be degraded by more than 50% in any natural water within 30 days. However, in the BOD test, biodegradation was diminished, with values of 40%, 20–30%, and 2–10% in river water, brackish water, and seawater, respectively. These results indicate that cellulose fibers are easily degraded into fine fragments, but it is difficult to cause their ultimate decomposition into water and carbon dioxide. Existence of such a tendency in the degree of biodegradation among the cellulose fibers remains unclear. The molecular weight of cellulose fibers in natural water was also measured during their degradation. The degradation behavior in river water and seawater was observed to be different from that in brackish water. The results thus obtained indicate that the microorganisms and enzymes that degrade cellulose fibers differ depending on the natural water, which influences the degree and mechanism of biodegradation.

     

para‐Phenylene‐Bridged Spirobi(triarylamine) Dimer with Four Perpendicularly Linked Redox‐Active π Systems

para‐Phenylene‐bridged spirobi(triarylamine) dimer 2 , in which π conjugation through four redox‐active triarylamine subunits is partially segregated by the unique perpendicular conformation, was prepared and characterized by structural, electrochemical, and spectroscopic methods. Quantum chemical calculations (DFT and CASSCF) predicted that the frontier molecular orbitals of 2 are virtually fourfold degenerate, so that the oxidized states of 2 can give intriguing electronic and magnetic properties. In fact, the continuous‐wave ESR spectroscopy of radical cation 2 ^.+ showed that the unpaired electron was trapped in the inner two redox‐active dianisylamine subunits, and moreover was fully delocalized over them. Magnetic susceptibility measurements and pulsed ESR spectroscopy of the isolated salts of 2 , which can be prepared by treatment with SbCl₅, revealed that the generated tetracation 2 ⁴⁺ decomposed mainly into a mixture of 1) a decomposed tetra(radical cation) consisting of a tri(radical cation) moiety and a trianisylamine radical cation moiety (≈75 %) and 2) a diamagnetic quinoid dication in a tetraanisyl‐p‐phenylendiamine moiety and two trianisylamine radical cation moieties (≈25 %). Furthermore, the spin‐quartet state of the tri(radical cation) moiety in the decomposed tetra(radical cation) was found to be in the ground state lying 30 cal mol^?1 below the competing spin‐doublet state.     

Determination of antihyperglycemic biguanides in serum and urine using an ion-pair solid-phase extraction technique followed by HPLC-UV on a pentafluorophenylpropyl column and on an octadecyl column

An HPLC-UV method was established for the determination of metformin and buformin in biological fluids. Metformin was not retained on particles packed in conventional solid-phase extraction cartridges; in contrast, buformin was retained too firmly and not eluted with a solvent for recovery. However, both drugs were retained on particles that had been treated with an ion-pair reagent of heptanesulfonate or dodecylsulfate and recovered almost completely. The recovered fraction was subjected to HPLC on a pentafluorophenylpropyl column which was suitable for the determination of both biguanides in serum and in urine. Limits of quantitation were low enough for clinical use, and reproducibility was high with an RSD of 0.9-2.3%. HPLC on a conventional octadecyl column was suitable only for the determination of buformin in serum since interfering peaks appeared on the chromatograms of urine samples. The method was applied to analysis of some clinical specimens.     

Computational simulations of HIV-1 proteases--multi-drug resistance due to nonactive site mutation L90M

Human immunodeficiency virus type 1 protease (HIV-1 PR) is one of the proteins that currently available anti-HIV-1 drugs target. Inhibitors of HIV-1 PR have become available, and they have lowered the rate of mortality from acquired immune deficiency syndrome (AIDS) in advanced countries. However, the rate of emergence of drug-resistant HIV-1 variants is quite high because of their short retroviral life cycle and their high mutation rate. Serious drug-resistant mutations against HIV-1 PR inhibitors (PIs) frequently appear at the active site of PR. Exceptionally, some other mutations such as L90M cause drug resistance, although these appear at nonactive sites. The mechanism of resistance due to nonactive site mutations is difficult to explain. In this study, we carried out computational simulations of L90M PR in complex with each of three kinds of inhibitors and one typical substrate, and we clarified the mechanism of resistance. The L90M mutation causes changes in interaction between the side chain atoms of the 90th residue and the main chain atoms of the 25th residue, and a slight dislocation of the 25th residue causes rotation of the side chain at the 84th residue. The rotation of the 84th residue leads to displacement of the inhibitor from the appropriate binding location, resulting in a collision with the flap or loop region. The difference in levels of resistance to the three inhibitors has been explained from energetic and structural viewpoints, which provides the suggestion for promising drugs keeping its efficacy even for the L90M mutant.     

Dispersion and separation of small-diameter single-walled carbon nanotubes

The dispersion of small-diameter single-walled carbon nanotubes (SWNTs) produced by the CoMoCAT method in tetrahydrofuran (THF) with the use of amine was studied. The absorption, photoluminescence, and Raman spectroscopies showed that the dispersion and centrifugation process leads to an effective separation of metallic SWNTs from semiconducting SWNTs. Since this method is simple and convenient, it is highly applicable to an industrial utilization for widespread applications of SWNTs.     

Hadamard transform capillary electrophoresis combined with laser-induced fluorometry using electrokinetic injection

Hadamard transform capillary electrophoresis (HTCE) based on electrokinetic injection allows laser-induced fluorescence detection using a small laser, namely the laser-diode-pumped YAG laser, as an excitation source. A small hole is fabricated at the center of a capillary by laser ablation; this hole functions as an inlet port for a sample solution. Therefore, the sample solution can be introduced electrophoretically into the capillary through the small hole. Multiple sample injection is accomplished by introducing a buffer solution from the end of the capillary and the sample solution through the hole. Both solutions are injected using two sets of high-voltage power supplies and migrate toward the opposite end of the capillary. A fluorescent analyte, rhodamine B, is successfully detected in the case of both single and multiple injection according to the Hadamard sequence code. By transforming the data encoded by the Hadamard matrix, the decoded data showed an increase in the signal-to-noise (S/N) ratio by a factor of 9.8. In the case of the sample containing two amino acids labeled with rhodamine B isothiocyanate (RBITC), although the concentration of every component including free RBITC is lower than the concentration limit of detection obtained by single injection, a substantial improvement in the sensitivity is achieved and all components are identified by the Hadamard transform technique.     

84% catalyst activity of water-assisted growth of single walled carbon nanotube forest characterization by a statistical and macroscopic approach

We propose a statistical and macroscopic analysis to estimate the catalyst activity of water-assisted growth (super-growth) of single-walled nanotubes (SWNT) and to characterize SWNT forests. The catalyst activity was estimated to be 84% (+/-6%), the highest ever reported. The SWNT forest was found to be a very sparse material where SWNTs represent only 3.6% of the total volume. This structural sparseness is believed to play a critical role in achieving highly efficient growth.     

Synthesis of pyrrolidine-fused [34]- and [36]octaphyrins via 1,3-dipolar cycloaddition

[reaction: see text] The utility of expanded porphyrins as a dipolarophile in cycloaddition reactions has been investigated. The 1,3-dipolar cycloaddition of meso-octakis(pentafluorophenyl)[36]octaphyrin(1.1.1.1.1.1.1.1) with an azomethine ylide provides mono- and bis-pyrrolidine-fused octaphyrins regio- and stereoselectively. Treatment of the cycloadduct with MnO(2) afforded [34]octaphyrin quantitatively.     

First total synthesis of (+/-)-Linderol A,a tricyclic hexahydrodibenzofuran constituent of Lindera umbellata bark,with potent inhibitory activity on melanin biosynthesis of cultured B-16 melanoma cells

The first total synthesis of (+/-)-Linderol A, a hexahydrodibenzofuran constituent of Lindera umbellata bark, with potent inhibitory activity on the melanin biosynthesis of cultured B-16 melanoma cells, was achieved through 19 steps of reaction in 6.6% overall yield, in which the critical step was a tandem reaction of a 3-ethoxycarbonylcoumarin derivative with dimethylsulfoxonium methylide to yield the 2-ethoxycarbonylcyclopenta[b]benzofuran-3-ol derivative.     

Ru(II)-catalyzed [2 + 2 + 2] cycloaddition of 1,2-bis(propiolyl)benzenes with monoalkynes leading to substituted anthraquinones

[2 + 2 + 2] cycloadditions of 1,2-bis(propiolyl)benzenes with monoalkynes were effectively catalysed by Cp*RuCl(cod) under mild conditions to give substituted anthraquinones in moderate to high yields.