Specific adenine alkylation by pyrrole-imidazole CBI conjugates

We examined DNA alkylation by pyrrole (Py)-imidazole (Im) hairpin polyamides, which possess 1,2,9,9a-tetrahydrocyclopropa[1,2-c]benz[1,2-e]indol-4-one (CBI) or cyclopropapyrroloindole (CPI) as DNA alkylating moieties. High-resolution denaturing gel electrophoresis revealed that alkylation by CBI conjugates 2 and 4 occurred specifically at adenines (A) in matched sequences, whereas CPI conjugates 1 and 3 alkylated both A and guanines (G) in matched sequences. The origin of the different reactivity of CBI and CPI conjugates is discussed in relation to the electrophilicity of the cyclopropane moiety. The high selectivity of the CBI conjugate gives additional sequence specificity relative to CPI conjugates that would be useful for the biological applications.     

Analysis of Vicinal Water in Soft Contact Lenses Using a Combination of Infrared Absorption Spectroscopy and Multivariate Curve Resolution

In this paper, we propose a new spectroscopic method to explore the behavior of molecules near polymeric molecular networks of water-containing soft materials such as hydrogels. We demonstrate the analysis of hydrogen bonding states of water in the vicinity of hydrogels (soft contact lenses). In this method, we apply force to hydrated contact lenses to deform them and to modulate the ratio between the signals from bulk and vicinal regions. We then collect spectra at different forces. Finally, we extracted the spectra of the vicinal region using the multivariate curve resolution-alternating least square (MCR-ALS) method. We report the hydration states depending on the chemical structures of hydrogels constituting the contact lenses.     

Mechanistic dichotomy in the solvent dependent access to E vs. Z-allylic amines via decarboxylative vinylation of amino acids

The solvent plays an important role in the photophysical properties of donor–acceptor based photocatalysts. The solvent-dependent access to E vs. Z-allylic amines was achieved via decarboxylative vinylation of amino acids with vinyl sulfones. Detailed experimental studies have been conducted to understand the role of the solvent in the reactivity and stereoselectivity of the vinylation reactions.

A solvent-dependent access to E vs. Z-allylic amines was achieved via decarboxylative vinylation of amino acids. Detailed experimental studies have been conducted to understand the role of the solvent in the reactivity and stereoselectivity of the vinylation reactions.     

Anvil design for slip-free high pressure deformation experiments in a rotational diamond anvil cell

A rotational diamond anvil cell is the most suitable deformation apparatus with which to investigate the rheological properties of deep-Earth materials at pressures similar to those found in the lower mantle and core. However, slip between the sample and piston is still a problem, since the slip prevents the attainment of a constant strain rate and interferes with the uniform deformation of a sample. In this paper, we report that using a diamond anvil with deep grooves results in a marked improvement in the coupling between the sample and the diamond anvils.     

Thermodynamic Control of Intramolecular Singlet Fission and Exciton Transport in Linear Tetracene Oligomers

We newly synthesized a series of homo- and hetero-tetracene (Tc) oligomers to propose a molecular design strategy for the efficient exciton transport in linear oligomers by promoting correlated triplet pair (TT) dissociation and controlling sequential exciton trapping process of individual doubled triplet excitons (T+T) by intramolecular singlet fission. First, entropic gain effects on the number of Tc units are examined by comparing Tc-homo-oligomers [(Tc)_n: n=2, 4, 6]. Then, a comparison of (Tc)_n and Tc-hetero-oligomer [TcF₃-(Tc)₄-TcF₃] reveals the vibronic coupling effect for entropic gain. Observed entropic effects on the T+T formation indicated that the exciton migration is rationalized by number of possible TT states increased both by increasing the number of Tc units and by the vibronic levels at the terminal TcF₃ units. Finally, we successfully observed high-yield exciton trapping process (trapped triplet yield: Φ_TrT=176 %).     

Crystal structure refinement of ReSi1.75 with an ordered arrangement of silicon vacancies

The crystal structure and microstructure of ReSi_1.75 were investigated by synchrotron X-ray diffraction combined with scanning transmission electron microscopy. ReSi_1.75 contains an ordered arrangement of vacancies in Si sites in the underlying tetragonal C11_b lattice of the MoSi₂-type and the crystal structure is monoclinic with the space group Cm. Atomic positions of Si atoms near vacancies are considerably displaced from the corresponding positions in the parent C11_b structure, and they exhibit anomalously large local thermal vibration accompanied by large values of atomic displacement parameter. There are four differently-oriented domains with two of them being related to each other by the 90° rotation about the c-axis of the underlying C11_b lattice and the other two being their respective twins. The habit planes for domain boundaries observed experimentally are consistent with those predicted with ferroelastic theory.     

Sequence-specific alkylation of double-strand human telomere repeat sequence by pyrrole-imidazole polyamides with indole linkers

We designed and synthesized pyrrole (Py)-imidazole (Im) hairpin polyamide 1-(chloromethyl)-5-hydroxy-1,2-dihydro-3H-benz[e]indole (seco-CBI) conjugates 1 and 2, which target both strands of the double-stranded region of the human telomere repeat sequences, 5'-d(TTAGGG)(n)-3'/5'-d(CCCTAA)(n)-3'. High-resolution denaturing polyacrylamide gel electrophoresis demonstrated that conjugates 1 and 2 alkylated DNA at the 3' A of 5'-ACCCTA-3' and 5'-AGGGTTA-3', respectively. Cytotoxicities of conjugates 1 and 2 were evaluated using 39 human cancer cell lines; averages of log IC(50) values for conjugates 1 and 2 were -6.96 (110 nM) and -7.24 (57.5 nM), respectively. Conjugates 1 and 2 have potential as antitumor drugs capable of targeting telomere repeat sequence.     

Total synthesis of (+/-)-clavubicyclone

[reaction: see text] The total synthesis of racemic clavubicyclone (1), which was isolated from Okinawan soft coral by our group, is described. The bicyclo[3.2.1]octane skeleton was prepared by Cope rearrangement of a divinylcyclopropane derivative. Three functional groups on the skeleton were constructed by Barton decarboxylation, Wittig reaction, and alkylation.     

Pressure effect on the electromotive force of the type R thermocouple

ABSTRACT

The pressure effect on the electromotive force (EMF) of a Pt13Rh–Pt (type R) thermocouple was examined to determine the temperature measurement accuracy of solid pressure medium apparatuses in high-pressure experiments. Single-wire EMFs were measured up to pressure of 13?GPa and temperature of 1173?K with a Kawai-type multi-anvil apparatus for Pt13Rh and Pt based on the single-wire method. The pressure conditions along the wires were evaluated by in situ X-ray diffraction using synchrotron X-ray radiation. The pressure effect of the Seebeck coefficients of Pt13Rh and Pt were determined by the analysis of the single-wire EMFs and pressure–temperature profiles along the wires and was virtually consistent with those determined in previous studies at lower pressures and temperatures. For type R thermocouple, the difference between the nominal and real temperatures was determined to be as large as –75?K at 13?GPa and 873?K.     

Cobalt‐Catalyzed Allylic Alkylation Enabled by Organophotoredox Catalysis

Co‐catalyzed allylic substitution reactions have received little attention, arguably because of the lack of any known advantage of Co catalysis over either Rh or Ir catalysis. Described here is a general and regioselective Co‐catalyzed allylic alkylation using an in situ catalyst activation by organophotoredox catalysis. This noble‐metal‐free catalytic system exhibits unprecedentedly high reactivities and regioselectivities for the allylation with an allyl sulfone, for the first time, representing the unique synthetic utility of the Co‐catalyzed method compared to the related Rh‐ and Ir‐catalyzed reactions.