Ultrafast dynamics of photoactive yellow protein via the photoexcitation and emission processes

Pump-dump fluorescence spectroscopy was performed for photoactive yellow protein (PYP) at room temperature. The effect of the dump pulse on the population of the potential energy surface of the electronic excited state was examined as depletion in the stationary fluorescence intensity. The dynamic behavior of the population in the electronic excited state was successfully probed in the various combinations of the pump-dump delay, the dump-pulse wavelength, the dump-pulse energy and the observation wavelength. The experimental results were compared with the results obtained by the femtosecond time-resolved fluorescence spectroscopy.     

Coherent oscillations in ultrafast fluorescence of photoactive yellow protein

The ultrafast photoinduced dynamics of photoactive yellow protein in aqueous solution were studied at room temperature by femtosecond fluorescence spectroscopy using an optical Kerr-gate technique. Coherent oscillations of the wave packet were directly observed in the two-dimensional time-energy map of ultrafast fluorescence with 180 fs time resolution and 5 nm spectral resolution. The two-dimensional map revealed that four or more oscillatory components exist within the broad bandwidth of the fluorescence spectrum, each of which is restricted in the respective narrow spectral region. Typical frequencies of the oscillatory modes are 50 and 120 cm(-1). In the landscape on the map, the oscillatory components were recognized as the ridges which were winding and descending with time. The amplitude of the oscillatory and winding behaviors is a few hundred cm(-1), which is the same order as the frequencies of the oscillations. The mean spectral positions of the oscillatory components in the two-dimensional map are well explained by considering the vibrational energies of intramolecular modes in the electronic ground state of the chromophore. The entire view of the wave packet oscillations and broadening in the electronic excited state, accompanied by fluorescence transitions to the vibrational sublevels belonging to the electronic ground state, was obtained.     

Pd-catalyzed asymmetric allylic amination of Morita-Baylis-Hillman adduct derivatives using chiral diaminophosphine oxides: DIAPHOXs

[reaction: see text] Asymmetric allylic amination of allylic carbonates prepared from racemic Morita-Baylis-Hillman adducts proceeded in the presence of Pd catalyst, chiral diaminophosphine oxide (DIAPHOX), and BSA, affording the corresponding chiral aza-Morita-Baylis-Hillman adduct derivatives in excellent yield with up to 99% ee. The cyclic reaction products could be converted into various synthetically useful compounds such as chiral cyclic beta-amino acids.     

Solvent dependence of absorption intensities and wavenumbers of the fundamental and first overtone of NH stretching vibration of pyrrole studied by near-infrared/infrared spectroscopy and DFT calculations

Near-infrared (NIR) and IR spectra were measured for pyrrole in CCl(4), CHCl(3), and CH(2)Cl(2) to study solvent dependence of absorption intensities and wavenumbers of the fundamental and first overtone of NH stretching vibration. It was found that the wavenumbers of the NH fundamental and its first overtone decrease in the order of CCl(4), CHCl(3), and CH(2)Cl(2), which is the increasing order for of the dielectric constant of the solvents. Their absorption intensities increase in the same order, and the intensity increase is more significant for the fundamental than the overtone. These results for the solvent dependence of the wavenumbers and absorption intensities of NH stretching bands of pyrrole are quite different from those due to the formation of hydrogen bonds. Quantum chemical calculations of the wavenumbers and absorption intensities of NH stretching bands by using the 1D Schr?dinger equation based on the self-consistent reaction field (SCRF)/isodensity surface polarized continuum model (IPCM) suggest that the decreases in the wavenumbers of both the fundamental and the overtone of the NH stretching mode with the increase in the dielectric constant of the solvents arise from the anharmonicity of vibrational potential and their intensity increases come from the gradual increase in the slope of the dipole moment function.     

Grafting of Polymers from Carbon Fiber. Anionic Graft Polymerization of Vinyl Monomers Initiated by Metallized Aromatic Rings on Carbon Fiber

The anionic graft polymerization of vinyl monomers onto carbon fiber initiated by metallized carbon fiber was investigated. The metalation of polycondensed aromatic rings of the carbon fiber surface was achieved by the treatment of carbon fiber with n-butyl-lithium (BuLi) in N, N, N′, N′ -tetramethylethylenediamine (TMEDA) or hexamethylphosphorous triamide (HMPT) at 0°C. The anionic polymerization of methyl methacrylate (MMA) and styrene (St) was initiated by the metallized carbon fiber, and these polymers were grafted onto the surface. The conversion and the percentage of grafting increased with increasing amount of BuLi used for the metalation of carbon fiber. When 0.20 g carbon fiber was treated with 0.3 mmol BuLi in TMEDA, the percentage of grafting of PMMA and PSt reached a maximum value (PMMA, 34.5%; PSt, 37.1 %). Furthermore, the metalation of aromatic rings of carbon fiber also proceeds by the treatment with BuLi in HMPT. On the contrary, no grafting was observed when carbon fiber was treated with BuLi in tetrahydrofuran (THF) or toluene. This may be due to the fact that metalation of carbon fiber does not proceed in THF or toluene.     

Oxidative kinetic resolution of racemic alkyl aryl carbinols by an electronically tuned chiral nitroxyl radical

A method for oxidative kinetic resolution of racemic alcohols catalyzed by chiral nitroxyl radical (R,R)-1 has been developed. This method is especially effective for the kinetic resolution of tert-butyl aryl carbinols (s = up to 23).     

Synthesis of fused-tricyclic indole derivatives through an acid-promoted skeletal rearrangement

We developed a novel method for synthesizing fused-tricyclic indole derivatives with a 3-aminomethyl indole motif through a reaction cascade involving ipso-Friedel–Crafts alkylation of phenols, rearomatization of the spirocyclohexadienone unit, and iso-Pictet–Spengler reaction. Using TFA as an acid promoter, six-, seven-, and eight-membered ring-fused indoles were obtained in 31–99% yield.     

Roles of surface nitrogen oxides in propene activation and NO reduction on Ag/Al2O3

The activation of propene in selective catalytic reduction (SCR) of NO on 4% Ag/Al₂O₃ has been studied by in situ infrared (IR) spectroscopy. Distinctive propene activation products were detected in the SCR of NO, depending on the nature of surface oxygen and nitrogen oxide species on Ag/Al₂O₃. C₃H₆ was oxidized to acetate species in an O₂ + C₃H₆ atmosphere on Ag/Al₂O₃ above 573 K. The addition of NO to the C₃H₆ + O₂ feed gas suppressed the formation of acetate species but increased the proportion of acrylate species. Acrylate species were further confirmed to be formed preferentially from C₃H₆ oxidation without the O₂ atmosphere on Ag/Al₂O₃ or nitrate-adsorbed Ag/Al₂O₃. On the other hand, adsorption of NO led to the formation of nitrito species on Ag/Al₂O₃, but the nitrito was barely oxidized to nitrate species unless there was an O₂ atmosphere at 473–673 K. Thus, the oxidation of propene to acetate species, or the formation of nitrate from nitrito, is attributed to two competitive electrophilic reactions. The formation of nitrate from nitrito species decreased electrophilic oxygen species that oxidized propene to acetate. Nevertheless, the first dehydrogenation of propene to form acrylate species on nitrate-adsorbed Ag/Al₂O₃ is a nucleophilic reaction, as it is on Ag/Al₂O₃. Furthermore, there was no decrease in reaction activity for formation of acrylate species on nitrate-adsorbed Ag/Al₂O₃ compared to Ag/Al₂O₃. This led to the total reaction occurring easily through the propene nucleophilic oxidation branch because the presence of the adsorbed nitrogen oxides changed selectively the formation rates of the surface reductants. IR spectra data further demonstrate that acrylate and acetate species, as the surface reductants, reacted with nitrate to generate isocyanate intermediates in the SCR of NO. The effect of structures of different reductants on NO reduction is discussed.     

Synthesis, characterization, DNA-binding study and anticancer properties of ternary metal(II) complexes of edda and an intercalating ligand

A series of ternary metal(ii) complexes {M(phen)(edda); 1a (Cu), 1b (Co), 1c (Zn), 1d (Ni); H(2)edda = N,N(')-ethylenediaminediacetic acid} of N,N'-ethylene-bridged diglycine and 1,10-phenanthroline were synthesized and characterized by elemental analysis, FTIR, UV-visible spectroscopy and magnetic susceptibility measurement. The interaction of these complexes with DNA was investigated using CD and EPR spectroscopy. MTT assay results of 1a-1c , screened on MCF-7 cancer cell lines, show that synergy between the metal and ligands results in significant enhancement of their antiproliferative properties. Preliminary results from apoptosis and cell cycle analyses with flow cytometry are reported. seems to be able to induce cell cycle arrest at G(0)/G(1). The crystal structure of 1a is also included.     

An artificial virus-like nano carrier system: enhanced endosomal escape of nanoparticles via synergistic action of pH-sensitive fusogenic peptide derivatives

We previously reported that transferrin (Tf)-modified liposomes (Tf-L) additionally modified with a cholesterylated pH-sensitive fusogenic peptide (Chol-GALA) can release an encapsulated aqueous phase marker to cytosol via endosomal membrane fusion. However, further obstacles need to be overcome to bring the Tf-L to the level of a viral-like gene delivery system. In this study, we developed a novel packaging method to encapsulate condensed plasmid DNA into PEgylated Tf-L (Tf-PEG-L) to form a core–shell-type nanoparticle. The most difficult challenge was to provide a mechanism of escape for the condensed core from endosome to cytosol in the presence of polyethylene glycol (PEG). We hypothesized that a membrane-introduced Chol-GALA and a PEgylated GALA would interact synergistically to induce membrane fusion between liposome and endosome. By simultaneously incorporating Chol-GALA into the membrane of Tf-PEG-L and GALA at tips of PEG chains, a condensed core was released into cytosol, and transfection acitivty increased 100-fold. We concluded that topological control was responsible for the synergistic effect of GALA derivatives introduced on Tf-PEG-L. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Kentaro Sasaki and Kentaro Kogure contributed equally to this work.