Temperature-controlled photooxygenation with polymer nanocapsules encapsulating an organic photosensitizer

A cross-linked poly- N-isopropylacrylamide (polyNIPAM) nanocapsule, TH@PC, containing thionine (TH), an organic photosensitizer, has been synthesized. This capsulated polymeric photosensitizer promotes a singlet oxygen oxygenation ( (1)O 2) accurately controlled by temperature: it shows high oxygenation activity at low temperature, but shows activity decrease with a rise in temperature, resulting in almost zero activity at >40 degrees C. The clear on-off activity control is driven by a heat-induced structure change of the capsule from the swollen single capsule to contracted state, and then to aggregate, behaving as an intelligent (1)O 2 filter. At low temperature, the capsule exists as the swollen single capsule, which allows (1)O 2 diffusion to bulk water, resulting in high oxygenation activity. A rise in temperature leads to contraction of the capsule, reducing the mesh size of the capsule wall. This suppresses (1)O 2 diffusion to bulk water and shows decreased activity. Intercapsule aggregation at >30 degrees C further suppresses (1)O 2 diffusion and shows almost no activity. The capsule promotes reversible activity control regardless of the heating/cooling process and can be reused with a simple recovery process.     

Biological selection of peptides for poly(l-lactide) substrates

Short peptides that recognize the alpha form of poly( l-lactide) (PLLA) crystalline films were identified from a phage-displayed peptide library. An enzyme-linked immunosorbent assay (ELISA) revealed that the apparent binding constants of the phage clones for the alpha form of PLLA were greater than those of the unselected phage library. The specificity index for the alpha form of PLLA referred to a structurally similar atactic poly(methyl methacrylate) (at-PMMA), supporting the alpha form of PLLA specific binding of the selected phage. Amino acid residues with proton-donor lateral groups and hydrophobic alkyl groups were relatively enriched in a sequence of heptapeptides on the specific phage clones, thereby suggesting the presence of hydrogen bonding as well as hydrophobic interactions between the alpha form of PLLA and the peptides. Surface plasmon resonance (SPR) analysis revealed that the binding constant of the freed c22 heptapeptide (Gln-Leu-Met-His-Asp-Tyr-Arg) for the alpha form of PLLA was greater than those for reference at-PMMA, amorphous PLLA, and the beta form of PLLA. It was found that c22 peptide can recognize slight differences in PLLA polymorphs such as a crystalline state and an arrangement of PLLA functional groups.     

Photocatalytic conversion of methane

Various efforts have been carried out to convert methane to more useful chemicals and hydrogen. However, due to its high stability, high energy is usually consumed for its conversion, which still remains as a problem to be solved. Recently, photocatalysis has been proposed to be one of the answers to break the thermodynamic barrier. This tutorial review provides a brief history about developments in the methane conversion and specially highlights the developments in the photocatalytic conversion of methane, such as methane coupling and methane conversion with other molecules.     

A new NCN pincer ruthenium complex and its catalytic activity for enantioselective hydrogenation of ketones

New bis(oxazolinyl)phenyl-ruthenium(II) complexes, which were synthesized by C-H bond activation with RuCl(3).3H(2)O in zinc powder and 1,5-cyclooctadine followed by ligand exchange reaction with sodium acetylacetonate or acetylacetone, exhibited enantioselective hydrogenation of ketones in up to 90% ee.     

Simultaneous determination of five polyether ionophores using liquid chromatography with one-step fluorescent derivatization

We present a selective method for simultaneous determination of five polyether ionophores such as salinomycin (SAL), monensin (MON), narasin (NAR), semduramicin (SEM) and lasalocid (LAS) in aquatic samples using a liquid chromatography with one-step fluorescent derivatization of 2-(4-hydrazinocarbonyl-phenyl) 4,5-diphenylimidazole (HCPI) and 4-(4,5-diphenyl-1H-imidazol-2-yl) benzoyl chloride hydrochloride (DIB-Cl). Fluorescent one-step derivatization for SAL, MON, NAR and SEM using HCPI and for LAS using DIB-Cl was monitored by an LC/fluorescence detector (E(x), 340 nm; E(m), 465 nm). Chromatographic separation was performed on a TSK-GEL ODS-120T (4.6 × 150 mm, 3 μm) column using a mobile phase of 0.1% formic acid in acetonitrile and 0.5 mM ammonium formate in water (70/30, v/v). The limits of detections were 0.01 μg/mL (50 pg) for LAS, 0.05 μg/mL (250 pg) for SAL, NAR and SEM, and 0.1 μg/mL (500 pg) for MON, respectively. The recoveries for water samples were indicated to be the range of 79.6 ± 6.4 - 99.0 ± 4.4% with associated precision values (between-day for 3 days) for repeatability. Based on solid-phase extraction, the limit of quantitation values indicated 0.1 ng/mL for SAL, MON, NAR and SEM, and 0.01 ng/mL for LAS in water samples.     

Investigation of the structure of cellulose in LiCl/DMAc solution and its gelation behavior by small-angle X-ray scattering measurements

Cellulose gels were prepared from cellulose in lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) solution. When the cellulose concentration in the solution is above the one at which cellulose molecules overlap, cellulose gels were formed. While the gel prepared by the addition of water was turbid, the one prepared by the ion exchange was colorless, transparent, and optically anisotropic. In order to explain this gelation behavior of cellulose, small-angle X-ray scattering (SAXS) measurements of the cellulose solutions and the gels were performed. The SAXS profiles of the cellulose solutions and the gels suggested that the large-scale fluctuation of the molecular chain density in the solution can be the origin of the molecular aggregates formed in the gel. Furthermore, the differences in the structure of the gels at the macroscopic and the molecular level were discussed in terms of the phase separation and the molecular association.     

High yielding methyl esterification catalyzed by indium(III) chloride

The carboxylic acids are efficiently converted into the methyl esters in methanol using indium(III) chloride as the catalyst. This method is applicable for aromatic and aliphatic carboxyl moieties as well as amino acids in high yields.     

Light-induced transformation of alkylurea derivatives in aqueous TiO2 dispersion

The light-induced degradation of alkylurea derivatives under simulated solar irradiation has been investigated in aqueous solutions containing TiO(2) as a photocatalyst. Herein, we will focus on how the presence of one or more methyl (or ethyl) groups on urea modifies the kinetics of disappearance and influences both the ratio and the extent of the inorganic nitrogen formation caused by different degradation pathways. In the present work, we have elucidated a mechanism for the formation of transformation products of the alkyl derivatives by combining several analytical and spectroscopic procedures and the theoretical simulation of ab initio calculations. In all cases, N-demethylation represents only a secondary pathway, while the main transformation proceeds through an unexpected cyclization, involving (m)ethyl- and di(m)ethylureas with the formation of (methyl)amino-2,3-dihydro-1,2,4-oxadiazol-3-one as the principal intermediate of the reaction (with a yield of 60 %). This behaviour is rather unexpected and in contrast with the typical photocatalyzed transformation pathways, which proceed through the formation of more simple structures.     

Synthesis of alpha-amino acid precursors directly from aldehydes using masked acyl cyanide reagents and N,O-dialkylated hydroxylamines

A synthetic methodology for the synthesis of alpha-amino acid precursors directly from the corresponding aldehydes using N,O-dialkylated hydroxylamines and masked acyl cyanide (MAC) reagents was developed. The one-pot reaction can be carried out under mild conditions and without a separate purification step of the imino species. The method was applied to the synthesis of optically pure (+)-4-methylphenylglycine and the derivatives by using an Abiko-Masamune's tricyclic 1,2-oxazolidine as the chiral auxiliary.