Synthesis and dilute aqueous solution properties of ester functionalized cationic gemini surfactants having different ethylene oxide units as spacer

New series of ester functionalized quaternary ammonium gemini surfactants having different ethylene oxide units as spacer have been synthesized and investigated for their aggregation behavior and thermodynamic properties of micellization by surface tension, conductivity, and fluorescence methods. The critical micelle concentration (cmc) of these gemini surfactants increases with the increase in the length of polar hydrophilic ethylene oxide spacer. The micellization process has been found to be entropy-driven and dependent on both the tendency of the hydrophobic group of the surfactants to transfer from aqueous environment to interior of micelle as well as the rearrangement of flexible ester-linked ethylene oxide units (hydrophilic spacer) into aqueous phase. The polar ester functional groups and pairs of nonbonding electrons on oxygen atom of ethylene oxide spacer form hydrogen bonding with water molecules enhancing their solubility in aqueous system.     

Preparation of tough hydrogels based on β-chitin nanofibers via NaOH treatment

Cellulose and chitin exist in nature as highly crystalline nanofibers. Previously, we reported preparing unique hydrogels from cellulose nanofibers by a simple NaOH treatment without use of any specific solvents or cross-linking agents. In the present study, a similar gel preparation was applied to β-chitin nanofibers extracted from purified squid pen powder. The crystal structure of chitin nanofibers was transformed from β-chitin to α-chitin by NaOH(aq) treatment above 30 wt%. The crystal conversion involving the interdigitation among adjacent nanofibers caused the formation of stable hydrogels with a α-chitin nanofiber network. The use of ethanol voided the dissolution during neutralization and enabled preparation of a higher crystalline hydrogel with high mechanical strength. It achieved a Young’s modulus of 16.6 MPa, a tensile strength of 7 MPa and a strain at break of 52.2 %, on average. Finally, we note that the shrinkage of the cellulose I and β-chitin nanofibers in aqueous NaOH solutions was caused by the release of tensile residual stress due to the intracrystalline swelling in NaOH solutions.     

Influence of drying method and precipitated salts on pyrolysis for nanocelluloses

The influence of bulk density and drying method on pyrolysis behavior was studied by focusing on the salt content within the nanocellulose (NC) materials. The thermogravimetric curves for NC materials were found to be almost identical between the different bulk densities via the various drying methods. It was therefore concluded that the bulk density and drying method of NC materials had little influence on pyrolysis behavior. By quantitating the remaining salt content within the sulfate-introduced cellulose nanocrystal materials, we discriminated between the sulfate groups bonded onto cellulose and precipitated sulfate from the solvent. The precipitated sulfate was found to accelerate the pyrolysis of NCs in common with the bonded sulfate groups, but in a different rate. These two types of sulfate within the NC materials should have the different catalytic ability on the dehydration of cellulose.     

Hybrid enriched bidiagonalization for discrete ill‐posed problems

The regularizing properties of the Golub–Kahan bidiagonalization algorithm are powerful when the associated Krylov subspace captures the dominating components of the solution. In some applications the regularized solution can be further improved by enrichment, that is, by augmenting the Krylov subspace with a low‐dimensional subspace that represents specific prior information. Inspired by earlier work on GMRES, we demonstrate how to carry these ideas over to the bidiagonalization algorithm, and we describe how to incorporate Tikhonov regularization. This leads to a hybrid iterative method where the choice of regularization parameter in each iteration also provides a stopping rule.     

Reconstituted biosynthesis of fungal meroterpenoid andrastin A

Andrastins (andrastin A-D), produced by several Penicillium species, exhibit inhibitory activity against ras farnesyltransferase, suggesting that these compounds could be promising leads for antitumor agents. Although the genome sequence of Penicillium chrysogenum, an andrastin-producing species, is available, the genetic and molecular bases for the biosynthesis of andrastins have not been elucidated. Here we report the identification and characterization of the gene cluster for andrastin biosynthesis. We reconstituted the biosynthetic pathway in Aspergillus oryzae, a fungal expression host, by the co-expression of five genes, including that of a terpene cyclase, and of four genes encoding the tailoring enzymes, required for the generation of andrastins. Remarkably, we successfully obtained andrastin A, the most complex andrastin molecule, as the metabolite of nine gene products, thus confirming the potential of the fungal expression system to synthesize useful natural products.     

Automatic polymerase chain reaction product detection system for food safety monitoring using zinc finger protein fused to luciferase

An automatic polymerase chain reaction (PCR) product detection system for food safety monitoring using zinc finger (ZF) protein fused to luciferase was developed. ZF protein fused to luciferase specifically binds to target double stranded DNA sequence and has luciferase enzymatic activity. Therefore, PCR products that comprise ZF protein recognition sequence can be detected by measuring the luciferase activity of the fusion protein. We previously reported that PCR products from Legionella pneumophila and Escherichia coli (E. coli) O157 genomic DNA were detected by Zif268, a natural ZF protein, fused to luciferase. In this study, Zif268–luciferase was applied to detect the presence of Salmonella and coliforms. Moreover, an artificial zinc finger protein (B2) fused to luciferase was constructed for a Norovirus detection system. In the luciferase activity detection assay, several bound/free separation process is required. Therefore, an analyzer that automatically performed the bound/free separation process was developed to detect PCR products using the ZF–luciferase fusion protein. By means of the automatic analyzer with ZF–luciferase fusion protein, target pathogenic genomes were specifically detected in the presence of other pathogenic genomes. Moreover, we succeeded in the detection of 10 copies of E. coli BL21 without extraction of genomic DNA by the automatic analyzer and E. coli was detected with a logarithmic dependency in the range of 1.0 × 10 to 1.0 × 10⁶ copies.     

Phosphorothioate Modification of mRNA Accelerates the Rate of Translation Initiation to Provide More Efficient Protein Synthesis

Messenger RNAs (mRNAs) with phosphorothioate modification (PS‐mRNA) to the phosphate site of A, G, C, and U with all 16 possible combinations were prepared, and the translation reaction was evaluated using an E. coli cell‐free translation system. Protein synthesis from PS‐mRNA increased in 12 of 15 patterns when compared with that of unmodified mRNA. The protein yield increased 22‐fold when the phosphorothioate modification at A/C sites was introduced into the region from the 5′‐end to the initiation codon. Single‐turnover analysis of PS‐mRNA translation showed that phosphorothioate modification increases the number of translating ribosomes, thus suggesting that the rate of translation initiation (rate of ribosome complex formation) is positively affected by the modification. The method provides a new strategy for improving translation by using non‐natural mRNA.     

Study of B0-->rho+/- pi-/+ time-dependent CP violation at Belle

We present a time-dependent analysis of CP violation in B0-->rho(+/-)pi(-/+) decays based on a 140 fb(-1) data sample collected at the Upsilon(4S) resonance with the Belle detector at KEKB. We obtain the charge asymmetry A(rhopi)(CP)=-0.16+/-0.10(stat)+/-0.02(syst). An unbinned maximum-likelihood fit to the Deltat distributions yields C(rhopi)=0.25+/-0.17(stat)+0.02-0.06(syst), DeltaC(rhopi)=0.38+/-0.18(stat)+0.02-0.04(syst), S(rhopi)=-0.28+/-0.23(stat)+0.10-0.08(syst), and DeltaS(rhopi)=-0.30+/-0.24(stat)+/-0.09(syst). The direct CP violation parameters for B-->rho(+)pi(-) and B-->rho(-)pi(+) decays are A(+-)(rhopi)=-0.02+/-0.16(stat)+0.05-0.02(syst) and A(-+)(rhopi)=-0.53+/-0.29(stat)+0.09-0.04(syst).     

Scaling relation for earthquake networks

The scaling relation, 2γ−δ=1, for the exponents of the power-law connectivity distribution, γ, and the power-law eigenvalue distribution of the adjacency matrix, δ, is theoretically predicted to be fulfilled by a locally treelike scale-free network in the “effective medium approximation” (i.e., an analog of the mean field approximation). Here, it is shown that such a relation holds well for the reduced simple earthquake networks (i.e., the network without tadpole-loops and multiple edges) constructed from the seismic data taken from California and Japan. This validates the goodness of the effective medium approximation in the earthquake networks and is consistent with the hierarchical organization of the networks. The present result may be useful for modeling seismicity on complex networks.