Millisecond analysis of double stranded DNA with fluorescent intercalator by micro-thermocontrol-device

Study of interaction between DNA and intercalator at molecular level is important to understand the mechanisms of DNA replication and repair. A micro-fabricated local heating thermodevice was adapted to perform denaturation experiments of DNA with fluorescent intercalator on millisecond time scale. Response time of complete unzipping of double stranded DNA, 16 μm in length, was measured to be around 5 min by commercial thermocycler. Response time of quenching of double stranded DNA with fluorescent intercalator SYBR Green was measured to be 10 ms. Thus, quenching properties owing to strand unzipping and denaturation at base pair level were distinguished. This method has provided easy access to measure this parameter and may be a powerful methodology in analyzing biomolecules on millisecond time scale.     

Bounding the Size of Equimatchable Graphs of Fixed Genus

A graph G is said to be equimatchable if every matching in G extends to (i.e., is a subset of) a maximum matching in G. In an earlier paper with Saito, the authors showed that there are only a finite number of 3-connected equimatchable planar graphs. In the present paper, this result is extended by showing that in a surface of any fixed genus (orientable or non-orientable), there are only a finite number of 3-connected equimatchable graphs having a minimal embedding of representativity at least three. (In fact, if the graphs considered are non-bipartite, the representativity three hypothesis may be dropped.) The proof makes use of the Gallai-Edmonds decomposition theorem for matchings.      

Magneto‐Structural Correlations in a 1,3,2‐Dithiazolyl Radical Crystal,BBDTA⋅GaBr4: Structure and Magnetic Properties of its Three Polymorphs

Three attractions in one cage : Various magnetic networks are formed in the three polymorphs of an organic magnet, BBTDA(=benzo[1,2‐d:4,5‐d′]bis[1,3,2]dithiazole)?GaBr₄. The three phases show quite different magnetic behaviors in spite of having the same chemical formula. Their magnetic differences originate from the relative configuration of the neighboring organic radical molecules in their crystals.

     

Copper(I) complexes with fluorinated hydrotris(pyrazolyl)borate: Influence of electronic effects on their structure,physicochemical properties,and reactivity

Copper(I) coordination complexes of the anionic fluorinated ligand, hydrotris(3-trifluoromethyl-5-methyl-1-pyrazolyl)borate (L0f⁻), i.e. the copper(I) carbonyl complex, [Cu^I(L0f)(CO)] (1), the copper(I) triphenylphosphine complex, [Cu^I(L0f)(PPh₃)] (2), the copper(I) acetonitrile complex, [Cu^I(L0f)(NCMe)] (3), and the corresponding copper(I) triphenylphosphine complex with hydrotris(3,5-diisopropyl-1-pyrazolyl)-borate anion (L1⁻), i.e. [Cu^I(L1)(PPh₃)] (4), were synthesized in order to investigate the influence of the electron-withdrawing groups on the pyrazolyl rings. The structures of complexes 1, 2, and 4 were determined by X-ray crystallography. While X-ray crystallography did not show definitive trends in terms of copper(I) atom geometry, the clear influence of the electronic structure of the pyrazolyl rings is observed by spectroscopic techniques, namely, IR and multinuclear NMR spectroscopy. Finally, the relative stability of the copper(I) complexes is discussed.     

Two-photon-excited fluorescence from silicate glass containing tantalum ions pumped by a near-infrared femtosecond pulsed laser

We report a novel phenomenon in sodium-calcium-silicate glass doped with Ta(5+). Under irradiation with a 780 nm femtosecond pulsed laser, strong blue emission centered at about 420 nm could be observed. The spectral characteristics are similar to those pumped by ultraviolet photons. The log-log correlation between integrated emission intensity and pump power reveals that a two-photon absorption process is involved in the phenomenon. It is suggested that the presence of localized Ta(5+)5d(0) energy levels is responsible for the appearance of the blue emission. The results indicate that transition metal ions without d electrons play an important role in fields of optics when embedded into glass hosts.     

Linearly polarized 100-kW-Peak-power pulsed fiber laser with a novel master oscillator

We report progress in the design and fabrication of a monolithic, linearly polarized, pulsed, Yb-doped fiber laser. This laser has a peak power of more than 100 kW, a tunable repetition rate from 100 kHz to 1 MHz, a tunable pulse duration from 2 ns to 2.5 μs, and a diffraction-limited, linearly polarized output beam with a mean power of 21 W and a wavelength of 1064 nm. A seed source that consists of a microchip Nd:YVO₄ laser and an electro optic deflector is developed. Using this source, the repetition rate and pulse duration are varied independently of each other. In addition, an excellent pulse-to-pulse repeatability is achieved.     

Separation‐free single‐base extension assay with fluorescence resonance energy transfer for rapid and convenient determination of DNA methylation status at specific cytosine and guanine dinucleotide sites

A separation‐free single‐base extension (SBE) assay utilizing fluorescence resonance energy transfer (FRET) was developed for rapid and convenient interrogation of DNA methylation status at specific cytosine and guanine dinucleotide sites. In this assay, the SBE was performed in a tube using an allele‐specific oligonucleotide primer (i.e., extension primer) labeled with Cy3 as a FRET donor fluorophore at the 5′‐end, a nucleotide terminator (dideoxynucleotide triphosphate) labeled with Cy5 as a FRET acceptor, a PCR amplicon derived from bisulfite‐converted genomic DNA, and a DNA polymerase. A single base‐extended primer (i.e., SBE product) that was 5′‐Cy3‐ and 3′‐Cy5‐tagged was formed by incorporation of the Cy5‐labeled terminator into the 3′‐end of the extension primer, but only if the terminator added was complementary to the target nucleotide. The resulting SBE product brought the Cy3 donor and the Cy5 acceptor into close proximity. Illumination of the Cy3 donor resulted in successful FRET and excitation of the Cy5 acceptor, generating fluorescence emission from the acceptor. The capacity of the developed assay to discriminate as low as 10% methylation from a mixture of methylated and unmethylated DNA was demonstrated at multiple cytosine and guanine dinucleotide sites.     

A new constitutive analysis of hexagonal close-packed metal in equal channel angular pressing by crystal plasticity finite element method

Most of hexagonal close-packed (HCP) metals are lightweight metals. With the increasing application of light metal products, the production of light metal is increasingly attracting the attentions of researchers worldwide. To obtain a better understanding of the deformation mechanism of HCP metals (especially for Mg and its alloys), a new constitutive analysis was carried out based on previous research. In this study, combining the theories of strain gradient and continuum mechanics, the equal channel angular pressing process is analyzed and a HCP crystal plasticity constitutive model is developed especially for Mg and its alloys. The influence of elevated temperature on the deformation mechanism of the Mg alloy (slip and twin) is novelly introduced into a crystal plasticity constitutive model. The solution for the new developed constitutive model is established on the basis of the Lagrangian iterations and Newton Raphson simplification.     

Imaging Doxorubicin Free Radical in Mice with Overhauser Enhanced MRI and its Tumor Suppression Effect in Mice

In the treatment with anticancer drugs, it is important to deliver an anticancer agent to target site of the tumor at an appropriate concentration. However, it is difficult to directly measure the distribution amount of the agent and effect of anticancer drug is evaluated using its tumor suppression effect. In this study, we report an approach to visualizing an anticancer agent distribution in tumor-bearing mouse model using Overhauser enhanced magnetic resonance imaging (OMRI). The agent, doxorubicin, is one of anthracycline anticancer drugs and can form a free radical at its quinone sites and could be visualized using OMRI. After direct injection into a tumor, doxorubicin free radical was successfully imaged in tumor-bearing mouse, demonstrating practical usefulness of OMRI in the study of pharmacodynamics of free radical compounds. Imaging of antitumor agent would be potentially useful as a guidance tool for image-guided-therapy of cancer local chemotherapy.