Estimated effects of silicone glue on protein crystal growth

Silicone glue (modified silicone polymer) is widely used for both experiments involving inorganic crystal growth and those involving organic materials like proteins. This material is very useful for building a hand-made experiment setup or for fixing protein crystals to specific locations. Though silicone glue is regarded as harmful to proteins, no systematic verification was performed to investigate its impurity effects on protein crystal growth. We focused on and estimated the impurity effects of silicone glue on protein crystal growth.     

Organotin perfluorooctanesulfonates as air-stable Lewis acid catalysts: synthesis, characterization, and catalysis

The reactions of 1,3-dichloro-1,1,3,3-tetrabutyldistannoxane and dialkyltin dihalides with silver perfluorooctanesulfonate provided the corresponding sulfonates as hydrates. The number of water molecules (n) of hydration was dependent on the conditions. The distannoxane derivative was identified as n from 0.5 to 6, while in the hydrated mononuclear species and DMSO complexes n varied widely from 4 to 13. 119Sn NMR spectroscopy and conductivity measurements indicated the ionic dissociation of these compounds in solution. These compounds exhibited unusually high solubility in polar organic solvents. The ionic dissociation together with facile hydration probably causes the unusual solubility. The Lewis acidity of these compounds was found to be high among organotin derivatives on the basis of ESR spectra of superoxide/metal-ion complexes. In contrast to well-known organotin triflates, these compounds suffered no hydrolysis upon storage in open air. The high catalytic activity of the distannoxane 1 was exemplified for various carbon-carbon bond-forming reactions, such as Mukaiyama-aldol as well as -Michael reactions and allylation of aldehydes.     

X-ray magnetic circular dichroism of size-selected, thiolated gold clusters

We report herein the X-ray magnetic circular dichroism (XMCD) at the Au L2,3 edges of a series of Au clusters protected by glutathione (GSH). The samples used here included AuN(SG)M with (N, M) = (10, 10), (15, 13), (18, 14), (22, 16), (25, 18), (29, 20), (39, 24) and a sodium gold(I) thiomalate (SGT) as a reference. Magnetic moments per cluster were found to be increased with size, whereas those per Au-S bond were nearly constant. This finding suggests that a localized hole created by Au-S bonding at the gold/glutathione interface, rather than the quantum size effect, is responsible for the spin polarization of gold clusters.     

Visible light sensitive photocatalyst, delafossite structured alpha-AgGaO(2)

Delafossite structured alpha-AgGaO(2) powder was successfully synthesized through a cation exchange reaction. alpha-AgGaO(2) has a band gap of 2.4 eV, absorbs visible light up to 520 nm, and effectively decomposes 2-propanol to CO2 via acetone by irradiating with either UV light (300-400 nm) or visible light (420-530 nm). The values of the quantum efficiency are similar (ca. 0.6%) under light irradiations with wavelengths of 365, 390, 430, 470, and 510 +/- 10 nm, but steeply decrease with wavelengths longer than 530 +/- 10 nm, which support a 2.4 eV band gap. In contrast, the other polymorph, alpha-AgGaO(2) powder, which has a band gap of 2.1 eV, shows a negligible activity when irradiating with either UV light or visible light. The higher oxidation activity of alpha-AgGaO(2) is probably due to its larger band gap, which is formed at the top of its valence band in a lower energy region as compared to alpha-AgGaO(2). Moreover, the first-principle calculations of alpha-AgGaO(2) and alpha-AgGaO(2) clearly indicate that alpha-AgGaO(2) has a remarkably larger dispersed valence band as compared to alpha-AgGaO(2), which is advantageous to the photocatalytic activity due to the efficient hole conduction.     

system with chiral SU(3) effective interaction

The K⁻pp system is investigated using a variational approach with realistic two-body interactions: the Argonne v18 NN potential and an energy dependent effective interaction derived from chiral SU(3) coupled-channel dynamics. Uncertainties in subthreshold extrapolations of the interaction are considered. A weakly bound K⁻pp state is found, with a binding energy B=(19±3) MeV substantially smaller than suggested in previous calculations. The decay width Γ(K⁻pp→πΣN) is estimated to range between about 40 and 70 MeV.     

Kinetics of Photoinduced Reactions at the Single-Molecule Level: The KACB Method

The kinetics of photoinduced reactions can be approached by laser flash photolysis techniques. Although such techniques allow for a detailed understanding of the important photophysics of molecules, they normally require a substantial amount of sample for measurements (>1 nmol), and thus, they are difficult to apply to analytical and diagnostic applications. The photophysics of a fluorescent molecule can be accessed by monitoring the kinetics of the fluctuation of fluorescence, which is called blinking. Blinking is a phenomenon that can be monitored only if molecules are observed at the single-molecule level. In bulk solution, blinking kinetics can be measured by using fluorescence correlation spectroscopy (FCS), which normally requires more than 10⁵ times less sample than that required for laser flash photolysis. Blinking is controlled to extract fruitful microenvironmental information around a fluorescent molecule, by using a method named kinetic analysis based on the control of fluorescence blinking (KACB). This Concept highlights the adaption of the KACB method to investigate the local conformation of DNA with less than 1 pmol of DNA sample.     

Radical grafting from glass fiber surface: Graft polymerization of vinyl monomers initiated by azo groups introduced onto the surface

This paper describes the radical graft polymerization of vinyl monomers from glass fiber surface initiated by alkylazo groups introduced onto the fiber surface. The introduction of azo groups onto the glass fiber surface was achieved by reaction of isocyanate groups which were previously attached onto the surface with two kinds of azo initiators, 4,4′-azobis(4-cyanopentanoic acid) (ACPA) and 2,2′-azobis(2-cyanopropanol) (ACP). The amounts of surface azo groups introduced by ACPA and ACP were both determined to be 1.3 × 10⁻⁵ mol g⁻¹ by nitrogen analysis. The radical graft polymerization of methyl methacrylate (MMA) was found to be initiated in the presence of the glass fiber having surface azo groups. During the polymerization, part of resultant poly(MMA) grafted onto the fiber surface through propagation of the polymer from the surface radicals produced by the decomposition of the azo groups. The percentage of grafting of poly(MMA) reached 48.1% after 24 h. The graft polymerizations of other monomers, such as styrene, N-vinylcarbazole, and acrylic acid, were also initiated by the surface azo groups, and the corresponding polymer effectively grafted onto the surface. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2121–2128, 1999     

The measured energy loss of high energy electrons in various metals

The energy distribution of electrons of about 53, 75 and 93 MeV has been measured before and after passing through Be, Sn and Gd absorbers of various thicknesses. Earlier data for Al, Cu and Pb absorbers are reviewed. The electrons were accelerated by the LINAC of the Naval Postgraduate School. The most probable energy loss and the half widths agree with the theory of Blunck and Westphal. An improved semi-empirical formula for the most probable energy loss is presented.