Preparation and mechanical properties of bacterial cellulose nanocomposites loaded with silica nanoparticles

Bacterial cellulose (BC), which is produced by Gluconacetobacter xylinus (Ga. xylinus) in culture, is made up of a three-dimensional network of ribbon-shaped bundles of cellulose microfibrils. In the current studies, we used two processes to prepare nanocomposites of BC filled with silica particles. In Process I, Ga. xylinus was incubated in medium containing silica sol Snowtex 0 (ST 0, pH 2–4) or Snowtex 20 (ST 20, pH 9.5–10.0). The elastic modulus at 20 °C was improved by keeping the amount of silica in the nanocomposites below 4% when ST 20 was used and below 8.7% when ST 0 was used. This process allowed incorporation of 50% silica in BC. Inclusion of higher amounts of silica reduced the modulus at 20 °C and the strength of the nanocomposites below that of BC. X-ray diffraction measurements revealed that the silica particles disturb the formation of ribbon-shaped fibrils and affect the preferential orientation of the ( ) plane. We also produced BC-silica nanocomposites by Process II, wherein the BC hydrogel was immersed in different concentrations of silica sols, allowing silica particles to diffuse into the BC hydrogel and lodge in the spaces between the ribbon-shaped fibrils. This method increased the modulus at 20°C and the strength compared to the BC matrix, but it was difficult to load the BC with more than 10% silica in this way.     

A finite element analysis of mach reflection by using the Boussinesq equation

The numerical analysis of ‘Mach reflection’, which is the reflection of an obliquely incident solitary wave by a vertical wall, is presented. For the mathematical model of the analysis, the two-dimensional Boussinesq equation is used. In order to solve the equation in space, the finite element method based on the linear triangular element and the conventional Galerkin method is applied. The combination of explicit and semi-implicit schemes is employed for the time integration. Moreover, one of the treatments for the open boundary condition, in which the analytical solution of the linearized Boussinesq equation in the outside domain is linked to the discrete values of velocity and water elevation in the inside domain, is applied for the modeling of the Mach reflection problem. © 1998 John Wiley & Sons, Ltd.     

Ultraviolet-visible and Surface-enhanced Raman Scattering Spectroscopy Studies on Ruthenium Phthalocyanine Monolayer Films Formed on Terephthalonitrile-modified Silver Substrates

A self-assembled monolayer film(SAM) of ruthenium phthalocyanine (RuPe) fabricated on a silver sub-strate premodified with an SAM of terephthalonitrile (TPN) was studied by means of surface-enhanced Ra-man seattering(SERS) and ultraviolet-visible (UV-Vis) speetroseopies. TPN was used as a ligand to linkRuPe since it can not only modify the silver suhstrate but also deliver the nitrile groups protruding from thesilver surface. Therefore, we can explore the relationship between the structure and the orientation of RuPeand the TPN-modified substrate. The UV-Vis spectra indicate a strong interaction between RuPe and TPN inthe composite film. The result is further confirmed by the SERS spectra of RuPe-TPN SAM, in which the vi-brational bands arising from both the RuPe and TPN moieties appear clearly, indicating that the RuPe is suc-cessfully assembled on the TPN film.     

Second Harmonic Generation Measurements for Biomacromolecules: Celluloses

The molecular chain orientation of mercerized cellulose II was examined by optical second harmonic generation (SHG) measurements. The SHG intensities of several kinds of mercerized cellulose II were found to be much larger than those expected for a structural model with an antiparallel molecular chain orientation as proposed by X-ray studies. This result suggests that the orientation of mercerized cellulose II is parallel as suggested by molecular dynamics simulation. © 2004 The Optical Society of Japan     

New method for preparing saturated and unsaturated aliphatic polyurethanes

Saturated and unsaturated aliphatic polyurethane were obtained from three different routes. In route 1, 1,4-dichloro-2-butene, sodium cyanate, and methanol were reacted to give dimethyl 2-butene-1,4-dicarbamate. This is hydrogenated easily to give dimethyl butane-1,4-dicarbamate. Ester exchange reaction of this compound with glycol gave saturated aliphatic polyurethane. In another procedure, route 2, 1,4-dichloro-2-butene, sodium cyanate and excess glycol were reacted to give bis(ω-hydroxyalkyl)-2-butene-1,4-dicarbamate. This was hydrogenated to give bis(ω-hydroxyalkyl)-butane-1,4-dicarbamate. A glycol elimination reaction gave poly(polymethylene tetramethyl-enedicarbamate). By route 3, 1,4-dichloro-2-butene, sodium cyanate, and glycol were reacted to give poly(polymethylene 2-butene-1,4-dicarbamate), a new unsaturated aliphatic polyurethane.     

Maedamide,a novel chymotrypsin inhibitor from a marine cyanobacterial assemblage of Lyngbya sp.

Maedamide, a novel chymotrypsin-inhibiting depsipeptide, was isolated from a cyanobacterial assemblage that mostly consisted of Lyngbya sp. Its structure was elucidated by spectroscopic analyses and chiral HPLC analyses of hydrolysis products. Maedamide selectively inhibited chymotrypsin but not elastase and trypsin. In addition, Maedamide strongly inhibited the growth of HeLa cells and HL60 cells.     

Phosphorylation of Inositols

Abstract

Chemical synthesis of inositol phosphates which are involved in a newly discovered intracellular transduction system is required. For this purpose, phosphorylation is a crucial step. However, phosphorylation of inositol derivatives which involve vicinally situated hydroxyl functions is quite difficult because of steric crowdness and easy formation of cyclic phosphate. This problem was solved by the following two methods. One method consists of the reaction of an inositol derivative with butyllithium and tetrabenzyl pyrophosphate. By this reaction, various inositol polyphosphates were obtained in good yields. The other involves a new phosphitylating agent, 2-diethylamino-1,3,2-benzodioxaphosphepine. Thus, inositols were first treated with the phosphoramidite in the presence of tetrazole and the resulting phosphites were oxidized by mCPBA to give the corresponding phosphates in excellent yields.     

Whole-body counter surveys of over 2700 babies and small children in and around Fukushima Prefecture 33 to 49 months after the Fukushima Daiichi NPP accident

BABYSCAN, a whole-body counter (WBC) for small children was developed in 2013, and units have been installed at three hospitals in Fukushima Prefecture. Between December, 2013 and March, 2015, 2707 children between the ages of 0 and 11 have been scanned, and none had detectable levels of radioactive cesium. The minimum detectable activities (MDAs) for ¹³⁷Cs were ≤3.5 Bq kg⁻¹ for ages 0–1, decreasing to ≤2 Bq kg⁻¹ for ages 10–11. Including the ¹³⁴Cs contribution, these translate to a maximum committed effective dose of ∼16 µSv y⁻¹ even for newborn babies, and therefore the internal exposure risks can be considered negligibly small.Analysis of the questionnaire filled out by the parents of the scanned children regarding their families’ food and water consumption revealed that the majority of children residing in the town of Miharu regularly consume local or home-grown rice and vegetables, while in Minamisoma, a majority avoid tap water and produce from Fukushima. The data show, however, no correlation between consumption of locally produced food and water and the children’s body burdens.     

2-烷基TCNQ的红外光谱和结构研究——CH_2剪式振动的双峰与晶体场分裂的关系(英文)

测量了2-烷基TCNQ(C8TCNQ,C12TCNQ,C18TCNQ)浇铸膜的红外光谱,发现这类化合物的红外CH2剪式振动在1 471和1 462 cm-1处显示2个峰。这2个峰的强度比(I1 471/I1 462)随着烷基链的长度增加而明显减少。另外,来自CH2的1 471 cm-1吸收峰与来自TCNQ环的1 529 cm-1吸收峰的相对强度随着碳链的长度增加而不发生变化。CnTCNQ系列化合物的红外光谱CH2的剪式振动行为与长链脂肪酸中CH2行为很不相同。在长链脂肪酸中,晶体场效应导致了剪式振动分裂。考虑C12TCNQ的晶体结构,而将1 471cm-1峰归属为非叉指对接的碳链,将1 462 cm-1峰归于叉指对接的碳链,双峰的出现与晶体场分裂无关。并且得到烷基TCNQ中,非叉指对接的碳链的长度与碳链总长度无关的结论。     

Carboxymethyl poly(L‐histidine) as a new pH‐sensitive polypeptide at endosomal/lysosomal pH

A carboxymethyl poly(L ‐histidine) has been synthesized as a new pH‐sensitive polypeptide at endosomal/lysosomal pH. Because of its poor water solubility at physiological pH, an application of poly(L ‐histidine) with a pK_a around 6.0 has been limited in spite of the native possession of the pH‐dependent property change at endosomal pH. Although the unmodified poly(L ‐histidine) suddenly precipitates out of the aqueous medium above pH 6.0 as the result of the deprotonation of the imidazole groups, the water solubility of the resulting carboxymethyl poly(L ‐histidine) has been improved at physiological pH. A solution turbidity measurement proved that no significant effect on a rapid aggregate formation or phase separation of serum proteins is induced by carboxymethyl poly(L ‐histidine). Hemolysis assay showed that the carboxymethyl poly(L ‐histidine) enhances membrane disruptive ability at endosomal/lysosomal pH. The cellular uptake of luciferase in the presence of the carboxymethyl poly(L ‐histidine) increases intracellular luciferase activity, which suggests that the carboxymethyl poly(L ‐histidine) makes the luciferase escape from lysosomal degradation. The carboxymethyl poly(L ‐histidine) would be the fundamental compound for designing various drug carriers with the pH sensitivity at endosomal/lysosomal pH. Copyright © 2007 John Wiley & Sons, Ltd.