Linear dichroism of Zn(II)-tetrapyridylporphine aggregates formed at the toluene/water interface

The apparent circular dichroism (CD) and the linear dichroism (LD) spectra of the aggregates of achiral zinc(II)-5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (ZnTPyP), formed at the toluene/water interface in a centrifugal liquid membrane (CLM) cell, were investigated by comparison with the microscopic CD and LD spectra of a single interfacial aggregate of ZnTPyP about 100 mum in length, measured by a microscope-spectropolarimeter. The interfacial ZnTPyP aggregate showed two types of flat trapezoidal shapes, one had a seedlike core at an edge (type I) and another a needlelike core at an edge (type II). The microscopic CD and LD spectra were observed by varying the angle between the parallel axis of the trapezoidal aggregate and the perpendicular axis of a polarized light for LD. The plot of the CD intensity against the LD intensity for a single aggregate, observed at a given wavelength, showed a rotated elliptical shape with a long axis through the origin, when the orientation angle was changed. From these results, it was concluded that the apparent CD spectra observed by the CLM-CD method were mainly due to the large linear dichroism of the aggregate. Both type I and type II structures showed two transition dipole moments, parallel and perpendicular to the long axis of the structure, but suggesting a more developed J-aggregate in type II structure. AFM measurements showed that the interfacial ZnTPyP aggregate had a multilayer structure, in which the unit monolayer thickness was 1.58 +/- 0.23 nm. Finally, the orientation angle of the interfacial aggregate in the CLM cell was estimated as 41 degrees -44 degrees to the rotating axis of the cell.     

Preparation of poly(N-isopropylacrylamide) emulsion gels and their drug release behaviors

Stimuli-sensitive drug delivery systems (DDSs) have attracted considerable attention in medical and pharmaceutical fields; thermosensitive DDS dealing with poly(N-isopropylacrylamide) (poly(NIPA)) have been widely studied. Novel NIPA emulsion gels, i.e., NIPA hydrogels containing distributed oil (oleyl alcohol) microdroplets, were synthesized by means of an emulsion-gelation method in which the polymerization of hydrogels in an aqueous phase in an oil-in-water (O/W) emulsion and the loading of a lipophilic drug (indomethacin) dissolved in an oil phase were accomplished simultaneously. The pulsatile (on-off) drug release from the NIPA emulsion gel loading indomethacin to a phosphate buffered saline (PBS) solution was successfully controlled by a temperature swing between 25 degrees C (release off) and 40 degrees C (release on). The mechanism of the pulsatile drug release was discussed in relation to the diffusion rate, distribution ratio, solvent exchange of NIPA hydrogels, and drug release from an NIPA organogel. The mechanism was as follows: the solvent exchange occurred within the NIPA emulsion gel (the NIPA gel-network absorbed oleyl alcohol with indomethacin) at temperatures above the LCST, and the diffusion rate of indomethacin through the solvent-exchanged gel was higher at 40 degrees C than at 25 degrees C.     

Enantioselective C--C bond formation to sulfonylimines through use of the 2-pyridinesulfonyl group as a novel stereocontroller

Enantioselective C--C bond formation to 2-pyridinesulfonylimines afforded products with good enantioselectivity. Dynamic induction of chirality on the sulfur by coordination of a chiral Lewis acid to the pyridine nitrogen and one of the prochiral sulfonyl oxygens induces enantioselectivity. Since the 2-pyridinesulfonyl group can easily be removed after the reaction, it acts not only as an activating group but also as an efficient stereocontroller.     

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.     

Dynamic interaction among the platform domain and two membrane-proximal immunoglobulin-like domains of class I major histocompatibility complex: normal mode analysis

Class I major histocompatibility complex (MHC) molecules have three domains, a platform domain and two membrane-proximal immunoglobulin-like domains, an alpha3 domain and a beta2-immunoglobulin (beta2m). To understand the dynamic interactions among the three domains, we simulated the behavior of a partial model deficient in beta2m and another model deficient in the alpha3 domain, by normal mode analysis. As a result, the partial model deficient in beta2m was more flexible in interdomain conformation than the other model. The lowest frequency modes (<2 cm(-1)) observed for the simulations of the partial model deficient in beta2m showed clear interdomain motions as if each domain moved like a rigid body. Such low frequencies and clear interdomain motions were not observed for the simulations of the other model, therefore the interdomain flexibility of the partial model deficient in beta2m may be due to the lowest frequency modes (<2 cm(-1)). These results suggest that beta2m contributes to maintaining the interdomain conformation of class I MHC molecules more than the alpha3 domain does, and may offer convincing evidence to support the notion that the alpha3 domain and beta2m do not have an equal influence on the structural stability of class I MHC molecules.     

Tareciliosides A--G: Cycloartane glycosides from leaves of Tarenna gracilipes (HAY.) OHWI

From the 1-BuOH-soluble fraction of a MeOH extract of leaves of Tarenna gracilipes, collected in Okinawa, seven new cycloartane glycosides, named tareciliosides A--G (4--10), were isolated together with three known compounds, D-mannitol (1), (R)-linalool 6-O-alpha-L-arabinopyranosyl-beta-D-glucopyranoside (2), and mussaenoside (3). Their structures were elucidated through a combination of spectroscopic analyses.     

Evaluation of single-base substitution rate in DNA by affinity capillary electrophoresis

Capillary electrophoretic separation of 60 mer single-stranded DNA (ssDNA) and a single-base-substituted ssDNA was demonstrated using a size- and composition-controlled poly(ethylene glycol)-oligodeoxyribonucleotide block copolymer (PEG-b-ODN) as an affinity ligand. Under appropriate conditions, PEG-b-ODN and ssDNA with a complementary sequence formed a reversible complex via hybridization during the electrophoresis, while the copolymer did not interact with the single-base-substituted ssDNA. The copolymer's PEG length determined the electrophoretic mobility of the ssDNA; upon formation of the complex, the electrically neutral PEG added hydrodynamic friction to ssDNA. Simultaneously using two types of PEG-b-ODN copolymers whose PEG segments were of different lengths, we achieved the complete separation of the 60 mer ssDNA, its single-base-substituted ssDNA, and impurities. This method was sensitive enough to quantify a slight amount (approximately 1%) of the single-base-substituted ssDNA. The present results suggest that our approach is applicable to quantitative detection of minor genotypes.     

Computation of the reduction free energy of coenzyme in aqueous solution by the QM/MM-ER method

In a recent development we proposed a quantum chemical approach to compute free energy change for chemical reactions in condensed phases by combining the QM/MM method with the theory of energy representation (QM/MM-ER). We extend in this Letter the novel approach to compute reduction free energy of isoalloxazine ring of FAD (flavin adenine dinucleotide) immersed in water within the framework of the QM/MM-ER method. The characteristic feature of our approach is that the excess electron to be attached on the FAD is identified as a solute. The reduction free energy has been obtained as −80.1 kcal/mol in the aqueous solution.     

Stability of atomic oxygen chemisorption on Pt‐alloy surfaces

A density functional theory calculation is used to investigate the atomic oxygen (O) stability over platinum (Pt) and Pt‐based alloy surfaces. Here, the stability is connected with the preferential adsorption sites for O chemisorptions and the adsorption energy. Thus, the interaction mechanism between atomic O and metal surfaces is studied by using charge transfer analysis. In this present paper, atomic structure and binding energy of oxygen adsorption on the Pt(111) are in a very good agreement with experiment and previous density functional theory calculations. Furthermore, we obtained that the addition of ruthenium (Ru) and molybdenum (Mo) on the pure Pt surface enhances the adsorption energy. Our charge transfer analysis shows that the largest charge transfer contributing to the metal‐O bonding formation is observed in the case of O/PtRuMo surface followed by O/PtRu surface. This is in consistency with metal d‐orbital characteristic, where Mo has much more empty d‐orbital than Ru in correspondence to accept electrons from atomic oxygen. Copyright © 2016 John Wiley & Sons, Ltd.     

Officinalioside,a new lignan glucoside from Borago officinalis L.

A new lignan glucoside, officinalioside (1), was isolated from n-BuOH fraction of the aerial parts of Borago officinalis L., together with four known compounds: actinidioionoside (2), roseoside (3), crotalionoside C (4) and kaempferol 3-O-β-D-galactopyranoside (5). The structure of the new compound was established by means of spectroscopic and chemical analyses. Compounds 1 and 2 showed a moderate DPPH radical scavenging activity (IC₅₀: 52.6 ± 1.70 and 41.3 ± 0.25 μM, respectively) comparable with that of the standard trolox (16.6 ± 2.2 μM) without any significant cytotoxicity towards human cell line A549 (IC₅₀ > 100 μM).