Synthesis and evaluation of C-glycosides as hydrotropes and solubilizing agents

This work presents expeditious synthesis of C-glycoside amphiphiles in aqueous media from unprotected di- or mono-saccharides. A Horner-Wadsworth-Emmons/Michael addition/Barbier allylation sequence led to C-glycosides that exhibit hydrotropic properties. The hydrotropic and solubilizing properties of these homoallylic alcohols including a β-C-glycoside moiety as well as additional β-C-glycosidic ketones with a short (C₇) alkyl chain are also described and compared with those of commercial O-glucoside references.     

Molecular imaging of membrane proteins and microfilaments using atomic force microscopy

Atomic force microscopy (AFM) is an emerging technique for a variety of uses involving the analysis of cells. AFM is widely applied to obtain information about both cellular structural and subcellular events. In particular, a variety of investigations into membrane proteins and microfilaments were performed with AFM. Here, we introduce applications of AFM to molecular imaging of membrane proteins, and various approaches for observation and identification of intracellular microfilaments at the molecular level. These approaches can contribute to many applications of AFM in cell imaging.     

Quantum reactive scattering of H + hydrocarbon reactions

A practical quantum-dynamical method is described for predicting accurate rate constants for general chemical reactions. The ab initio potential energy surfaces for these reactions can be built from a minimal number of grid points (average of 50 points) and expressed in terms of analytical functionals. All the degrees of freedom except the breaking and forming bonds are optimised using the MP2 method with a cc-pVTZ basis set. Single point energies are calculated on the optimised geometries at the CCSD(T) level of theory with the same basis set. The dynamics of these reactions occur on effective reduced dimensionality hyper-surfaces accounting for the zero-point energy of the optimised degrees of freedom. Bonds being broken and formed are treated with explicit hyperspherical time independent quantum dynamics. Application of the method to the H + CH(4)--> H(2)+ CH(3), H + C(2)H(6)--> H(2)+ C(2)H(5), H + C(3)H(8)--> H(2)+n-C(3)H(7)/H(2)+i-C(3)H(7) and H + CH(3)OH --> H(2)+ CH(3)O/H(2)+ CH(2)OH reactions illustrate the potential of the approach in predicting rate constants, kinetic isotope effects and branching ratios. All studied reactions exhibit large quantum tunneling in the rate constants at lower temperatures. These quantum calculations compare well with the experimental results.     

The Ni + O2 reaction: a combined IR matrix isolation and theoretical study of the formation and structure of NiO2

The reaction of Ni atoms with molecular oxygen has been reinvestigated experimentally in neon matrices and theoretically at the DFT PW91PW91/6311G(3df) level. Experimental results show that i) the nature of the ground electronic state of the superoxide metastable product is the same in neon and argon matrices, ii) two different photochemical pathways exist for the conversion of the superoxide to the dioxide ground state (involving 1.6 or 4 eV photons) and iii) an important matrix effect exists in the Ni + O(2)--> Ni(O(2)) or ONiO branching ratios. Theoretical results confirm that the electronic ground state of the metastable superoxide corresponds to the singlet state, in agreement with former CCSD(T) calculations, but in contradiction with other recent works. Our results show that the ground electronic state of the dioxide is (1)Sigma(+)(g) with the lowest triplet and quintet states at slightly higher energy, consistent with the observation of weak vibronic transitions in the near infrared. The potential energy profiles are modelled for the ground state and nine electronic excited states and a pathway for the Ni(triplet) + O(2)(triplet) --> Ni(O(2)) or ONiO (singlet) reaction is proposed, as well as for the Ni(O(2)) --> ONiO photochemical reaction, accounting for the experimental observations.     

The Ni2+O2 reaction: the IR spectrum and structure of Ni2O2. A combined IR matrix isolation and theoretical study

The formation of Ni2O2 can be observed from the condensation of effusive beams of Ni and O2 in neon or argon matrices. Observation of 58Ni(2)16O2, 58Ni60Ni16O2, 60Ni2(16)O2, Ni(2)18O2 and Ni(2)16O18O isotopic data for five fundamental transitions enable a discussion of structural parameters for matrix-isolated Ni2O2 in its cyclic ground state. Analysis of the nickel isotopic effects on the 58,60Ni2(16)O18O fundamentals suggest an elongated rhombic structure with a Ni-O bond force constant (240+/-10 N m-1) and NiONi bond angles around 79 degrees. The latter points to a Ni-Ni internuclear distance shorter than the O-O one. Low-lying singlet, triplet and quintet states have been studied using density functional theory with an unrestricted wave function and broken symmetry formalism. The high spin states and closed shell singlet states have been also investigated at the CCSD(T) level. The Ni2O2 ground state is calculated to be an antiferromagnetic singlet state with all the hybrid functionals. The first order properties (energies, geometry) calculated with a hybrid functional are very similar when different exchange-correlation functionals with different exact exchange fractions are used and the calculated ground state geometry (NiONi bond angle near 80 degrees, NiO bond distance around 179.5 pm) is in good agreement with the experimental estimate. Nevertheless, a correct reproduction of the experimental vibrational properties is found only when a hybrid functional containing an exact exchange fraction in the 0.4-0.5 range is used. The orbital and topological bonding analyses of Ni2O2 reveal that the relatively short Ni-Ni internuclear distance within the molecule should not be interpreted as a remaining metal-metal bonding interaction, but clearly indicate that the bonding driving force is due to the formation of four strong and highly polarized Ni-O bonds. Even in such an early stage of metal oxidation, the Ni-Ni interaction has virtually disappeared.     

The first total synthesis of xenitorins B and C: assignment of absolute configuration

Starting from (-)-beta-pinene, the first total synthesis of xenitorins B and C has been accomplished, which also allowed the assignment of their absolute configuration.     

Investigation of field emission and photoemission properties of high-purity single-walled carbon nanotubes synthesized by hydrogen arc discharge

Single-walled carbon nanotubes (SWCNTs) were directly synthesized by a hydrogen arc-discharge method by using only Fe catalyst. The synthesized carbon materials indicated high-purity SWCNTs without amorphous carbon materials from SEM observation. The SWCNTs had diameters of 1.5-2.0 nm from TEM and Raman observation. After a simple purification, TGA indicated that SWCNTs had a purity of ca. 90.1 wt %. Field emission from the SWCNT emitters which were fabricated by using a spray method was measured by a diode structure. The vertically aligned SWCNT emitters showed the low turn-on voltage of 0.86 V/microm and a high emission-current density of 3 mA/cm2 at an applied field of about 3 V/microm. From a Fowler-Nordheim plot, the vertically aligned SWCNT revealed a high field enhancement factor of 2.35 x 10(4). The photoemission measurements, excited by a photon energy of 360 eV, showed significantly delocalized graphite-pi states at the purified SWCNTs. Here, we investigated that the field-emission properties of SWCNTs would be attributed to the high electronic density of states near Fermi energy, including the delocalized graphite-pi states.     

Surface characterization of argon-plasma-modified perfluorosulfonic acid membranes

The perfluorosulfonic acid membranes which are used in direct methanol fuel cells were modified with argon plasma under various conditions, and the physicochemical and transport properties of the resulting membranes were investigated using various analytical techniques. The plasma treatment was found to change the surface morphology and physicochemical properties of the membranes. The surface roughness of the membranes was increased by the etching effect of plasma. From the FTIR and XPS analyses, the incorporation of new oxygen functionalities, such as the peroxide group, was confirmed. The breakage of both the sulfonic acid groups and ether linkages were also found to cause an increase in the equivalent weight of the modified skin layer of the membrane. The incident water contact angle of the modified membrane in a dry state decreased with an increased plasma treatment, because of the hydrophilic groups that developed on the membrane surface. The time-dependent water contact angle, however, increased in proportion to the extent of the plasma treatment, due to the reduced concentration of sulfonic acid groups. Although the equilibrium water uptake of the modified membrane was almost invariable because of the negligible thickness of the modified skin layer, the transport properties of the membrane such as methanol permeability and proton conductivity were significantly reduced.     

Viscosity Results for a Class of Evolution Inclusions with Maximal Monotone Operators

In the finite dimensional setting, we investigate the existence of viscosity subsolutions of Hamilton–Jacobi–Bellman equations related to control problems subject to evolution inclusions governed by time-dependent maximal monotone operators with Young measures.     

Favorite sites of randomly biased walks on a supercritical Galton–Watson tree

Erd?s and Révész (1984) initiated the study of favorite sites by considering the one-dimensional simple random walk. We investigate in this paper the same problem for a class of null-recurrent randomly biased walks on a supercritical Galton–Watson tree. We prove that there is some parameter $\kappa \in (1,\infty ]$ such that the set of the favorite sites of the biased walk is almost surely bounded in the case $\kappa \in (2,\infty ]$, tight in the case $\kappa =2$, and oscillates between a neighborhood of the root and the boundary of the range in the case $\kappa \in (1,2)$. Moreover, our results yield a complete answer to the cardinality of the set of favorite sites in the case $\kappa \in (2,\infty ]$. The proof relies on the exploration of the Markov property of the local times process with respect to the space variable and on a precise tail estimate on the maximum of local times, using a change of measure for multi-type Galton–Watson trees.