Unexpected preference of the E. coli translation system for the ester bond during incorporation of backbone-elongated substrates

There have been recent advances in the ribosomal synthesis of various molecules composed of nonnatural ribosomal substrates. However, the ribosome has strict limitations on substrates with elongated backbones. Here, we show an unexpected loophole in the E. coli translation system, based on a remarkable disparity in its selectivity for beta-amino/hydroxy acids. We challenged beta-hydroxypropionic acid (beta-HPA), which is less nucleophilic than beta-amino acids but free from protonation, to produce a new repertoire of ribosome-compatible but main-chain-elongated substrates. PAGE analysis and mass-coupled S-tag assays of amber suppression experiments using yeast suppressor tRNAPheCUA confirmed the actual incorporation of beta-HPA into proteins/oligopeptides. We investigated the side-chain effects of beta-HPA and found that the side chain at position alpha and R stereochemistry of the beta-substrate is preferred and even notably enhances the efficiency of incorporation as compared to the parent substrate. These results indicate that the E. coli translation machinery can utilize main-chain-elongated substrates if the pKa of the substrate is appropriately chosen.     

Revised structures of gambiriins A1, A2, B1, and B2, chalcane-flavan dimers from gambir (Uncaria gambir extract)

Gambir, the aqueous extract from Uncaria gambir (Rubiaceae), has been used as an astringent medicine in Asian countries. Investigation of the constituents in the extract led to the isolation of four chalcane-flavan dimers, gambiriin A1 (6), A2 (7), B1 (8), and B2 (9), in addition to (+)-catechin (1), (+)-epicatechin (2), and dimeric proanthocyanidins, procyanidin B1 (3), procyanidin B3 (4), and gambiriin C (5). The spectroscopic and chemical data obtained in the present study indicated that their previously proposed structures 6a, 7a, 8a, and 9a should be revised to 6, 7, 8, and 9, respectively.     

Evaluation of the radioactivity in concrete from accelerator facilities

For evaluation of radioactivity induced in the concrete samples from accelerator facilities, the residual radioactivity in concrete sample, collected from seven accelerator facilities, was determined by γ-ray spectrometry. The tritium was extracted by the heating method using an IR furnace, and measured with a liquid scintillation counter. It was found that the major radioisotopes activated mainly by neutrons in the concrete samples were ¹⁵²Eu, ⁶⁰Co, ¹³⁴Cs and ³H. The concentrations of radioactivities induced by thermal neutron capture are the highest at a depth of 10 cm in the concrete wall. The correlation between tritium, ⁶⁰Co and ¹⁵²Eu activity was investigated by measuring many concrete samples for seven accelerator facilities. The results indicate that their activities are strongly correlated with each other. So it would also be concluded that the total activity in shielding concrete could be estimated on the basis of the activities of ⁶⁰Co and ¹⁵²Eu.     

Adsorption of fission products onto soils using a fission multitracer

The adsorption behavior of fission products to various soils was studied using a multitracer. The multitracer was prepared by neutron irradiation of ²³⁵U. Distribution coefficients of fission products were obtained for seventeen kinds of Japanese soils. It was found that zirconium, niobium, and rare earth elements show high distribution coefficients for all soil samples, however, elements like alkali metals show varied values.     

New approaches to enantioselective fluorination: Cinchona alkaloids combinations and chiral ligands/metal complexes

The selective construction of carbon-fluorine bonds is of great interest to medicinal chemists because the replacement of a hydrogen or an oxygen atom with a fluorine atom in biologically active molecules can confer the molecules with improved physicochemical properties and biological activities. Since the first discovery of enantioselective fluorination using N-fluorocamphorsultam, our synthetic interest had been focused on the development of chiral N-fluorosulfonamide derivatives capable of enantioselective fluorination. However, these initial efforts revealed several limitations in both chemical yields and enantioselectivities of the fluorinated products. We present here the background of our personal story of the enantioselective fluorination reaction and some successful applications of the methods to the design and synthesis of biologically active products. Two novel approaches using cinchona alkaloid/Selectfluor^® combinations and chiral ligands/metal complexes have been pursued, respectively. In addition, the recent advances in this area by other groups are also described briefly.     

Evaluating a time-delay of hydrogen production quantitatively in photosynthetic bacteria for stabilizing intermittency

Renewable energy is regarded as a clean energy source but has some problems, one of which is intermittency. To reduce this, the time-delay of hydrogen production by photosynthetic bacteria can be effective. In this study, we qualitatively evaluated the time-delay of hydrogen production by photosynthetic bacteria under various irradiation conditions, and we also quantitatively evaluated it by fitting the experimental data and the hydrogen production model with a genetic algorithm. As a result of model fitting, we found that the relationship between the lengths of the optimized time-delay of hydrogen production by photosynthetic bacteria and the amount of light irradiation is linear. And we also found that the time-delay of hydrogen production by photosynthetic bacteria had an upper limit under low light intensity. We have suggested the existence of an energy store mechanism in photosynthetic bacteria.     

Pd‐initiated polymerization of diazo compounds bearing dialkoxyphosphinyl group and hydrolysis of the resulting polymers and oligomers to afford phosphonic acid‐containing products

Pd‐initiated polymerization and oligomerization of diazo compounds containing a dialkoxyphosphinyl group are described. Polymerization of 2‐dialkoxyphosphinylethyl diazoacetates with π‐allylPdCl‐based initiating systems afforded C? C main chain polymers bearing phosphonate on each main chain carbon atom. The quantitative transformation of the side chain phosphonate to phosphonic acid resulted in the formation of water soluble polymers having the acid groups accumulated around their main chains, although the carbonyl ester linkage in the side chain was cleaved via intramolecular acid‐assisted hydrolysis in water at 80 °C. Pd‐initiated oligomerization of diethyl diazomethylphosphonate yielded an oligomeric product bearing diethoxyphosphiny groups directly attached to its main chain carbons, with unexpected incorporation of azo group in the main chain framework. Hydrolysis of the phosphonate of the oligomer afforded a water‐soluble product, which was revealed to show higher proton conductivity than poly(vinylphosphonic acid) under certain conditions. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1742–1751     

Solution properties of perfluorinated anionic surfactants with divalent counterion of separate electric charges

Novel surfactants of perfluorinated double long-chain salts with divalent counterion of separate electric charge, 1,1-(1,omega-alkanediyl)bispyridinium diperfluorononanoate (CnBP(FC9)2, n = 2, 4, 6, 8) were newly synthesized. Their solution properties were investigated by surface tension measurement over the temperature range from 298.2 to 313.2 K, where magnesium diperfluorononanoate (Mg(FC9)2) was employed as a reference surfactant with divalent counterion of concentrated electric charge. From change of surface tension with concentration, the critical micelle concentration (CMC), surface excess (Gamma), apparent molecular surface area (A), and -log(concentration to reduce surface tension of water by 20 mN m-1) (pC20) were determined. The CMC values of CnBP(FC9)2 decreased with increasing charge separation and with increasing temperature, where the values of CnBP(FC9)2 were much smaller than those of Mg(FC9)2. In addition, the pC20 values of the former were also much larger than those of the latter. These results indicate a strong influence of the extent of charge separation or the spacer length of the counterions upon surface activity of the fluorinated surfactants. The surface excess or the corresponding apparent molecular surface area monotonously changed with the spacer length (n < or = 6), whereas the behavior for n = 8 was much different from the other CnBP(FC9)2 due to conformational change in the in-between alkanediyl chain. The entropy changes (Deltas) for the surface adsorption or condensation were found to be mostly negative for CnBP(FC9)2, where the changes approached zero with an increase in the charge separation. On the other hand, the changes for Mg(FC9)2 were positive over the whole concentration below the CMC. In addition, Brewster angle microscopy indicated no condensation of the present surfactants just at the air/solution interface.     

Iridium‐Catalyzed Enantioselective C?H Alkylation of Ferrocenes with Alkenes Using Chiral Diene Ligands

The first catalytic and enantioselective C H alkylation of ferrocene derivatives with various alkenes was achieved. A cationic iridium complex, having a chiral diene ligand, and an isoquinolyl moiety as a directing group are essential for regioselective and enantioselective C H bond activation.