Direct measurement of the dynamics of excess electron transfer through consecutive thymine sequence in DNA

Charge transfer in DNA is an essential process in biological systems because of its close relation to DNA damage and repair. DNA is also an important material used in nanotechnology for wiring and constructing various nanomaterials. Although hole transfer in DNA has been investigated by various researchers and the dynamic properties of this process have been well established, the dynamics of a negative charge, that is, excess electron, in DNA have not been revealed until now. In the present paper, we directly measured the rate of excess electron transfer (EET) through a consecutive thymine (T) sequence in nicked-dumbbell DNAs conjugated with a tetrathiophene derivative (4T) as an electron donor and diphenylacetylene (DPA) as an electron acceptor at both ends. The selective excitation of 4T by a femtosecond laser pulse caused the excess electron injection into DNA, and led to EET in DNA by a consecutive T-hopping mechanism, which eventually formed the DPA radical anion (DPA(?-)). The rate constant for the process of EET through consecutive T was determined to be (4.4 ± 0.3) × 10(10) s(-1) from an analysis of the kinetic traces of the ΔO.D. during the laser flash photolysis. It should be emphasized that the EET rate constant for T-hopping is faster than the rate constants for oxidative hole transfers in DNA (10(4) to 10(10) s(-1) for A- and G-hopping).     

“Triple Observation Method (TOM)” to Discriminate Optically Autofluorescence from Porphyrins Versus that from Copper-Metallothioneins

We propose a conclusive difference observed between the excitation conditions required to observe porphyrins and copper-metallothioneins in cells and/or tissues using an ordinary fluorescence microscope. We have emphasized the importance of examining the spectral properties of the emissions to avoid any serious mistakes such as confusing porphyrins with copper-metallothioneins in the liver and kidneys. However, microspectrophotometry is not a conventional method for either histochemical, cytochemical, or pathological studies because microspectrophotometers are both expensive and difficult to operate. Therefore, we demonstrate a simple comparative method using ordinary excitation filter arrangements. When using our technique, it becomes possible to optically discriminate more accurately between the autofluorescence properties arising from porphyrins and those arising from copper-metallothioneins. We would like to name our simple technique “Triple Observation Method (TOM)”.     

Inhibitory effects of constituents from Morus alba var. multicaulis on differentiation of 3T3-L1 cells and nitric oxide production in RAW264.7 cells

A new arylbenzofuran, 3',5'-dihydroxy-6-methoxy-7-prenyl-2-arylbenzofuran (1), and 25 known compounds, including moracin R (2), moracin C (3), moracin O (4), moracin P (5), artoindonesianin O (6), moracin D (7), alabafuran A (8), mulberrofuran L (9), mulberrofuran Y (10), kuwanon A (11), kuwanon C (12), kuwanon T (13), morusin (14), kuwanon E (15), sanggenon F (16), betulinic acid (17), uvaol (18), ursolic acid (19), β-sitosterol (20), oxyresveratrol 2-O-β-D-glucopyranoside (21), mulberroside A (22), mulberroside B (23), 5,7-dihydroxycoumarin 7-O-β-D-glucopyranoside (24), 5,7-dihydroxycoumarin 7-O-β-D-apiofuranosyl-(1→6)-O-β-D-glucopyranoside (25) and adenosine (26), were isolated from Morus alba var. multicaulis Perro. (Moraceae). Their structures were determined by spectroscopic methods. The prenyl-flavonoids 11-14, 16, triterpenoids 17,18 and 20 showed significant inhibitory activity towards the differentiation of 3T3-L1 adipocytes. The arylbenzofurans 1-10 and prenyl-flavonoids 11-16 also showed significant nitric oxide (NO) production inhibitory effects in RAW264.7 cells.     

Reconstitution of bacterial photosynthetic unit in a lipid bilayer studied by single-molecule spectroscopy at 5 K

As a model of photosynthetic unit (PSU), self-assembled aggregates of pigment-protein complexes from photosynthetic bacteria were prepared in a lipid bilayer by reconstitution of the light-harvesting 2 (LH2) complex and light-harvesting 1-reaction center (LH1-RC) complex through detergent removal of their micelles in the presence of lipids. By performing polarization-controlled fluorescence and fluorescence-excitation spectroscopy on single aggregates at a temperature of 5 K, the composition of individual aggregates was determined and excitation energy transfer (EET) between constituent complexes was observed. LH2 and LH1-RC from a bacterium, Rhodobacter (Rb.) sphaeroides, were found to form a trimeric aggregate in which EET takes place from one LH2 to two LH1-RCs. In contrast, a heterodimer of LH2 and LH1-RC in which EET works was found to assemble from a combination of complexes of different bacterial species, that is, LH2 from Rb. sphaeroides and LH1-RC from Rhodopseudomonas (Rps.) palustris.     

Discrimination in festival games with limited observability and accessibility

This paper provides an analysis of discrimination and prejudices from the perspective of inductive game theory. We extend the festival game, originally given by Kaneko-Matsui, to include new constraints on the observability of ethnic identities and on accessible locations for players. We characterize the Nash equilibrium set, which reveals a different variety of segregation patterns and discriminatory behavior. In order to facilitate the analysis of discrimination and prejudices, we introduce a measure of discrimination, which chooses a representative equilibrium with the smallest degree of discrimination. Using this measure, we discuss various new phenomena, such as discrimination in an ethnic hierarchy; similar ethnicities as discriminated and as discriminating; and mutual discrimination. The introduction of limited observability and accessibility enables us to obtain those results.     

Synthesis of uniform and dispersive calcium carbonate nanoparticles in a protein cage through control of electrostatic potential

We have synthesized calcium carbonate nanoparticles (Ca-NPs) in the cavity of a cage-shaped protein, apoferritin, by regulating the electrostatic potential of the molecule. The electrostatic potential in the cavity was controlled by pH changes resulting from changes in the dissolved carbon dioxide (CO(2)) concentration in the reaction solution. Recombinant L-apoferritin was mixed with a suspension of calcium carbonate (CaCO(3)), and the mixture was pressurized with gaseous CO(2) at 2 MPa. The pH of the solution decreased from 9.3 to 4.4; the CaCO(3) dissolved during pressurization, and then precipitated after the pressure was reduced to ambient. After repeating the pressurization/depressurization process three times, about 70% of the apoferritin molecules were found to contain nanoparticles with an average diameter of 5.8 ± 1.2 nm in their cavity. Energy-dispersive X-ray spectroscopy and electron diffraction analysis showed that the nanoparticles were calcite, one of the most stable crystal forms of CaCO(3). Electrostatic potential calculations revealed a transition in the potential in the apoferritin cavity, from negative to positive, below pH 4.4. The electrostatic potential change because of the change in pH was crucial for ion accumulation. Since the Ca-NPs synthesized by this method were coated with a protein shell, the particles were stably dispersed in solution and did not form aggregates. These Ca-NPs may be useful for medical applications such as synthetic bone scaffolds.     

Tandem addition-cyclization of o-ethynylphenyllithiums and isoselenocyanates: a convenient preparation of functionalized benzo[c]selenophenes

The o-bromoethynylbenzenes were lithiated with tert-BuLi in Et₂O followed by treatment with isoselenocyanate, and then EtOH was added as a proton source, producing the desired (Z)-3-methylidenebenzo[c]selenophenes as the sole 5-exo-dig mode cyclization products in one-pot with yields ranging from 54-87%. The iodocyclization of the o-ethynylphenyllithium with isoselenocyanate stereoselectively gave the (E)-1′-iodo-3-methylidenebenzo[c]selenophene, which was converted into the more functionalized benzo[c]selenophenes via the Suzuki- and Sonogashira-coupling reactions.     

Optimizing coverage of metal oxide nanoparticle prepared by pulsed laser deposition on nonenzymatic glucose detection

Metal oxide nanoparticles prepared by pulsed laser deposition (PLD) were applied to nonenzymatic glucose detection. NiO nanoparticles with size of 3 nm were deposited on glassy carbon (GC) and silicon substrates at room temperature in an oxygen atmosphere. Transmission electron microscope (TEM) image showed nanoparticles with the size of 3 nm uniformly scattered on the Si(0 0 1) substrate. Unlike co-sputtering nanoparticle and carbon simultaneously, the PLD method can easily control the surface coverage of nanoparticles on the surface of substrate by deposition time. Cyclic voltammetry was performed on the samples deposited on the GC substrates for electrochemical detection of glucose. The differences between peak currents with and without glucose was used to optimize the coverage of nanoparticles on carbon electrode. The results indicated that optimal coverage of nanoparticles on carbon electrode.     

Behavior of oxygen in zinc oxide films through thermal annealing and its effect on sheet resistance

Behavior of oxygen in sputtering deposited ZnO films through thermal annealing and its effect on sheet resistance of the films were investigated. The crystallinities of the ZnO film were improved by post-deposition annealing in vacuum. However, the sheet resistance of ZnO film was dramatically decreased after post-deposition annealing in vacuum at more than 300 °C, while O₂ desorbed from the film. The oxygen vacancies which acted as donors were formed by the thermal annealing in vacuum. The sheet resistance of the films was recovered by annealing in oxygen ambient. In this paper, ¹⁸O₂ gas as an oxygen isotope was used as the annealing ambient in order to distinguish from ¹⁶O, which was constituent atom of the ZnO films. SIMS analysis revealed that ¹⁸O diffused into the ZnO film from the top surface by ¹⁸O₂ annealing. Therefore oxygen vacancies formed by the post-deposition annealing in vacuum could be compensated by the annealing in oxygen ambient.     

Photodissociation of pyrene dimer radical cation during the pulse radiolysis–laser flash photolysis combined method

Photodissociation of pyrene (Py) dimer radical cation (Py ₂ ^?+ ) giving pyrene radical cation (Py^?+) and Py and subsequent regeneration of Py ₂ ^?+ by association of Py^?+ and Py were directly observed during the pulse radiolysis–laser flash photolysis combined method at room temperature. When Py ₂ ^?+ was excited at the local excitation band with the 532-nm laser flash, the rapid growth and decay of monomeric Py^?+ were observed at 460 nm. The dissociation of Py ₂ ^?+ proceeded via a one-photon process to give the ground-state Py^?+(D₀) and Py in the quantum yield (Φ_diss) of (2.9 ± 0.9) × 10^?3. It was shown that Py^?+ decayed with a time constant of several tens of nanoseconds, indicating that the association of Py^?+ with Py regenerating Py ₂ ^?+ proceeds at a diffusion-controlled rate. The photodissociation proceeded from the lowest excited state of Py ₂ ^?+ , even when Py ₂ ^?+ was excited to the higher excited state. The difference between the Φ_diss value of Py ₂ ^?+ and that previously reported for naphthalene dimer radical cation (Np ₂ ^?+ ) is discussed.