High-field 1H MAS and 15N CP-MAS NMR studies of alanine tripeptides and oligomers: distinction of antiparallel and parallel beta-sheet structures and two crystallographically independent molecules

beta-Strand peptides are known to assemble into either antiparallel (AP) or parallel (P) beta-sheet forms which are very important motifs for protein folding and fibril formations occurring in silk fibroin or amyloid proteins. Well-resolved 1H NMR signals including NH protons were observed for alanine tripeptides (Ala)3 with the AP and P structures as well as (Ala)n (n = 4-6) by high-field/fast magic-angle spinning NMR. Amide NH and amino NH3+ 1H signals of (Ala)3 with the P structure were well resonated at 7.5 and 8.9 ppm, respectively, whereas they were not resolved for the AP structure. Notably, NH 1H signals of (Ala)3 and (Ala)4 taking the P structure are resonated at higher field than those of the AP structure by 1.0 and 1.1 ppm, respectively. Further, NH 15N signals of (Ala)3 with the AP structure were resonated at lower field by 2 to 5 ppm than those of (Ala)3 with the P structure. These relative 1H and 15N hydrogen bond shifts of the P structure with respect to those of the AP structure are consistent with the relative hydrogen bond lengths of the interstrand N-H...O=C bonds. Distinction between the two crystallographically independent chains present in the AP and P structures was feasible by 15N chemical shifts but not by 1H chemical shifts because of insufficient spectral resolution in the latter. Calculated 1H and 15N shielding constants by density functional theory are generally consistent with the experimental data, although some discrepancies remain depending upon the models used.     

Dispersion Theory for Two-phase Layered-Geometry Nanocomposites

A dispersion theory for linear optical properties of two-phase layered-geometry nanocomposites is presented. Generalized dispersion relations and sum rules are stated using the results from complex analysis. The concept of Lorentzian linear susceptibility is exploited in theoretical treatment of the effective linear susceptibility of the nanocomposite. The meromorphism of total reflectance in the case of effective meromorphic nonlinear susceptibility was observed.     

Direct Introduction of a Dimesitylboryl Group Using Base‐Mediated Substitution of Aryl Halides with Silyldimesitylborane

The first dimesitylboryl substitution of aryl halides with a silylborane bearing a dimesitylboryl group in the presence of alkali‐metal alkoxides is described. The reactions of aryl bromides or iodides with Ph₂MeSi?BMes₂ and Na(OtBu) afforded the desired aryl dimesitylboranes in good to high yields and with high borylation/silylation ratios. Selective reaction of the sterically less‐hindered C?Br bond of dibromoarenes provided monoborylated products. This reaction was used to rapidly construct a D‐π‐A aryl dimesityl borane with a non‐symmetrical biphenyl spacer.     

siRNA-mediated Knockdown of the Heme Synthesis and Degradation Pathways: Modulation of Treatment Effect of 5-Aminolevulinic Acid-based Photodynamic Therapy in Urothelial Cancer Cell Lines

Photodynamic therapy mediated by 5-aminolevulinic acid (ALA-PDT) has been developed as a therapeutic modality for refractory superficial bladder cancers. Here, in experiments using urothelial cancer cell lines, we investigated the effects of siRNA modulating heme-synthetic and degradation pathways for ALA-PDT. Targeted knockdown of ferrochelatase (FECH) suppressed heme synthesis and significantly increased intracellular protoporphyrin IX (PpIX) accumulation, leading to enhanced phototoxicity in four of five cell lines. Heme oxygenase-1 (HO-1) is recognized as important for cytoprotection against oxidative stress such as PDT. Targeted knockdown of HO-1 leads to decreased intracellular PpIX accumulation, resulting in a failure to enhance ALA-PDT effect in four cell lines. Knockdown of HO-1 caused marked growth inhibition in UM-UC-2 overexpressing HO-1, whereas no inhibitory effect was observed in UM-UC-3 lacking HO-1 expression. Moreover, HO-1 protein levels and (GT) _n repeat polymorphism of the HO-1 gene promoter region were examined with the implication that the constitutive expressions of HO-1 protein were associated with a shorter (GT) _n repeat. Our results suggested that (1) FECH siRNA improved the phototoxicity of ALA-PDT, (2) overexpression of HO-1 was associated with shorter (GT) _n repeat of the promoter region, and (3) siRNA-mediated knockdown of HO-1 could suppress the growth of bladder cancer cells overexpressing HO-1.     

Histidine-tagged shiga toxin B subunit binding assay: simple and specific determination of gb3 content in mammalian cells

A two-step binding assay for globotriaosylceramide (Gb3) content was developed by histidine-tagging strategy, which is a well-established method for the purification of recombinant proteins. The complete binding of the recombinant His-tagged Shiga toxin 1B subunit (1B-His) (1 microg/ml) to the standard Gb3 adsorbed on a multi-well H type plate was observed within 30 min at 37 degrees C; and its binding could be visualized by the following applications of HisProbe-HRP (8 microg/ml) and tetramethylbenzidine (TMB) peroxidase substrate. The 1B-His binding assay was linear over the range of 1 to 100 ng of Gb3 per well. The binding of 1B-His was specific to Gb3 separated from HeLa cells, and no major cross-reactivity of other glycolipids in Folch's lower fractions extracted from HeLa cells was detected. The glycolipids in Folch's lower fractions from HeLa cells, human fibroblasts and mouse heart were suitable for this assay, but the further purification was needed for glycolipids from human plasma, thus sample preparation is critical factor for the reliable determination of Gb3 content. The 1B-His binding to Gb3 was inhibited by the addition of galactose, but not mannose. This 1B-His binding assay will be useful not only for the determination of Gb3 content, but also for screening for the compounds which inhibit the toxin-binding to Gb3. The strategy of our present method may be applicable for other binding assay, such as Cholera toxin B-subunit for ganglioside GM1.     

Evidence of Nonelectrochemical Shift Reaction on a CO-Tolerant High-Entropy State Pt-Ru Anode Catalyst for Reliable and Efficient Residential Fuel Cell Systems

A randomly mixed monodispersed nanosized Pt-Ru catalyst, an ultimate catalyst for CO oxidation reaction, was prepared by the rapid quenching method. The mechanism of CO oxidation reaction on the Pt-Ru anode catalyst was elucidated by investigating the relation between the rate of CO oxidation reaction and the current density. The rate of CO oxidation reaction increased with an increase in unoccupied sites kinetically formed by hydrogen oxidation reaction, and the rate was independent of anode potential. Results of extended X-ray absorption fine structure spectroscopy showed the combination of N(Pt-Ru)/(N(Pt-Ru) + N(Pt-Pt)) ? M(Ru)/(M(Pt) + M(Ru)) and N(Ru-Pt)/(N(Ru-Pt) + N(Ru-Ru)) ? M(Pt)/(M(Ru) + M(Pt)), where N(Pt-Ru)(N(Ru-Pt)), N(Pt-Pt)(N(Ru-Ru)), M(Pt), and M(Ru) are the coordination numbers from Pt(Ru) to Ru(Pt) and Pt (Ru) to Pt (Ru) and the molar ratios of Pt and Ru, respectively. This indicates that Pt and Ru were mixed with a completely random distribution. A high-entropy state of dispersion of Pt and Ru could be maintained by rapid quenching from a high temperature. It is concluded that a nonelectrochemical shift reaction on a randomly mixed Pt-Ru catalyst is important to enhance the efficiency of residential fuel cell systems under operation conditions.     

Radical Copolymerization of Vinylidene Chloride with 3(2-Methyl)-6-methylpyridazinone in Several Solvents

The radical copolymerization of vinylidene chloride (Vc, M₁) with 3(2-methyl)-6-methylpyridazinone (I, M₂) was carried out in benzene, ethanol, phenol, and acetic acid at 60 and 80°C. The monomer reactivity ratios were found to vary with the reaction conditions. The linear correlationships were obtained by plotting the values of log r₁ against those of ^V C[dbnd]O and ^V C[dbnd]C of monomers determined in the solvents.     

Mapping analyses of Fe-diffused mc-Si using M?ssbauer microscope and photoluminescence

Twenty CK chondrites collected in the Antarctica Continent were characterized by inductively-coupled plasma mass spectrometry (ICP-MS), prompt gamma ray analysis (PGA), instrumental neutron activation analysis (INAA), X-ray diffractometry (XRD) and ⁵⁷Fe-M?ssbauer spectroscopy. As a result of elemental analysis, it was revealed that 18.2~26.4 mass% of iron was included in the each chondrite. M?ssbauer spectrum of LEW86258, classified as a typical CK chondrite, was found to be composed of two paramagnetic doublets and two magnetic sextets. M?ssbauer spectra were assigned to the absorption due to forsterite (Mg_1.36Fe_0.64SiO₄) and magnetite (Fe₃O₄), as also confirmed by XRD. XRD study of LAP03834, reclassified from CK to R chondrite, revealed the presence of crystalline phase due to forsterite. These results indicate that LAP03834 and related chondrites, i.e., MET01149, LAP03923 and MAC02453, should be reclassified as R or LL chondrite.     

Finite element analysis of density flow using the velocity correction method

A finite element method is proposed for the analysis of density flow which is induced by a difference of density. The method employs the idea that density variation can be pursued by using markers distributed in the flow field. For the numerical integration scheme, the velocity correction method is successfully used, introducing a potential for the correction of velocity. This method is useful because one can use linear interpolation functions for velocity, pressure and potential based on the triangular finite element. The final equations can be formulated using the quasi-explicit finite element method. A flume in a tank with sloping bottom has been analysed by the present method. The computed results show extremely good agreement with the experimental observations.