Search

We conducted femtosecond transient absorption spectroscopy of oxymyoglobin (MbO2) in the wavelength region of 450–750 nm to observe the charge transfer (CT) state of the heme in MbO2. The transient absorption spectrum just after photoexcitation (t= 0–0.25 ps) was assigned to superposition of S1–Snabsorption (450–750 nm) and ground-state bleaching (540 and 580 nm) of MbO2. At t> 0.25 ps, a new absorption band appeared at around 680 nm with the decay time of ∼5 ps. This broad absorption band was similar to that of a porphyrin cation. Hence, we concluded that this absorption band was attributed to the ligand-to-metal charge transfer (LMCT) state of the heme. The proposed photophysical pathways suggested that formation of the LMCT state was the key event in the excited state relaxation of the heme in MbO2. [ABSTRACT FROM AUTHOR]

Genetic factors have been suggested to be involved in suicide. Although some genetic factors, such as serotonergic transduction, have been associated with suicide, the results are inconsistent. There is a possibility that various signaling anomalies are involved in the biological vulnerability to suicide. We carried out a genome-wide gene-expression study in the brains of suicide victims using DNA microarrays;14-3-3 ε, which is related to neurogenesis, was one of the genes upregulated in the brains of suicide victims in the microarray analysis. This was confirmed by Western blot analysis. To examine the possibility of the involvement of 14-3-3 ε in the pathogenesis of suicide, we investigated the association of the 14-3-3 ε gene and completed suicide. We used three high-frequency SNPs (rs1532976, rs3752826, and rs9393) and found a significant association of two alleles (rs1532976 and rs3752826) with completed suicide ( p< 0.05). Moreover, the distribution of haplotype revealed a more significant difference between completed suicide and controls ( p=0.0005). This finding suggests that 14-3-3 ε is a potential suicide susceptibility gene and implies that dysregulation of neurogenesis may be involved in suicide. [ABSTRACT FROM AUTHOR]

Hybridization of complementary single-stranded DNAs (ssDNA) at a water/CCl4 interface was studied on the basis of picosecond total internal reflection fluorescence spectroscopy. Complementary ssDNAs dissolved in water were shown to produce the relevant double-stranded DNA (dsDNA) at a water/CCl4 interface in the presence of octadecylamine (ODA) in the oil phase, while hybridization between ssDNAs did not proceed in the water phase, as demonstrated by the fluorescence dynamics of ethidium bromide as a probe for the DNA structure. The structures of dsDNA and the roles of ODA in hybridization of ssDNA at the interface were discussed. [ABSTRACT FROM AUTHOR]

Temperature (T)-dependent emission from [{Mo6X8}(n-C3F7COO)6]2- (X = Cl (1), Br (2), and I (3)) in optically transparent polyethylene glycol dimethacrylate matrices were studied in 3 K < T < 300 K to elucidate the spectroscopic and photophysical properties of the clusters, in special reference to zero-magnetic-field splitting (zfs) in the lowest-energy excited triplet states (T1) of the clusters. The cluster complexes 1 and 2 showed the T-dependent emission characteristics similar to those of [{Mo6Cl8}Cl6]2-, while 3 exhibited emission properties different completely from those of 1 and 2. Such T-dependent emission characteristics of 1, 2, and 3 were explained successfully by the excited triplet state spin-sublevel (Φn, n = 1-4) model. The zfs energies between the lowest-energy (Φ1) and highest-energy (Φ4) spin sublevels, ΔE14, resulted by the first-order spin-orbit coupling, were evaluated to be 650, 720, and 1000 cm-1 for 1, 2, and 3, respectively. The emission spectra of 1, 2, and 3 in CH3CN at 298 K were reproduced very well by the ΔE14 values and the population percentages of Φn at 300 K. We also report that the ΔE14 values of the clusters correlate linearly with the fourth power of the atomic number (Z) of X: ΔE14 ∝ {Z(X)}4. [ABSTRACT FROM AUTHOR]

The dynamic and static phase separation behavior in aqueous poly(N-isopropylacrylamide) (PNIPAM) solutions is highly sensitive to the tacticity of PNIPAM. We investigated the phase separation dynamics of aqueous solutions of PNIPAM with different tacticities (atactic and syndiotactic-rich types) and found that the phase separation dynamics of syndiotactic-rich PNIPAM was much different from that of atactic-type PNIPAM. First, phase separation in syndiotactic-rich PNIPAM was faster. Second, there was a critical point (Ccp) in the concentration dependence of the phase separation rate: the phase separation accelerated dramatically when the solution concentration was higher than 2.0 wt % (= Ccp). Third, syndiotactic-rich PNIPAM required a higher thermal energy for phase separation compared to atactic PNIPAM. Such behavior can be explained on the basis of the high hydrophobicity of syndiotactic-rich PNIPAM in a dehydrated state and a diffusion-controlled aggregation model. The present study shows that precise control of the stereoregularity will open new channels toward the design and development of stimuli-responsive-polymer-based smart materials. [ABSTRACT FROM AUTHOR]

The electrochemical, spectroscopic, and phophysical properties of a series of Ru(II) complexes having a triarylborane-appended 2,2′-bipyridine (bpy) ligand(s) (RuBbpys: [Ru(Bbpy)n(bpy)3–n]2+ (B1n) and [Ru(B2bpy)n(bpy)3–n]2+ (B2n), B = (dimesityl)boryldurylethynyl group(s) at the 4- or 4,4′-position(s) in bpy, n = 1–3) are described. In the excited states of the complexes, the intramolecular charge transfer transitions between the π-orbital of the aryl group and the vacant p-orbital on the boron atom (π(aryl)–p(B) CT) synergistically interact with the metal-to-ligand charge transfer (MLCT) transitions. The molar absorption coefficient of the MLCT band (ε(MLCT)) of the complex increased with increasing n, and B23 showed extremely intense absorption with ε(MLCT) = 5.6 × 104 M–1 cm–1 at 488 nm. Furthermore, B23 showed the highest emission quantum yield (0.43) among those of the polypyridine Ru(II) complexes hitherto reported. As one of the interesting results, we report that the radiative rate constant of B2n shows the correlation with ε(MLCT). The effects of the synergistic MLCT/π(aryl)–p(B) CT interactions on the spectroscopic and photophysical characteristics of RuBbpys are discussed in detail. [ABSTRACT FROM AUTHOR]

Strongly luminescent mixed-metallic copper(I)–silver(I) coordination polymers with various Cu/Ag ratio were prepared by utilizing the isomorphous relationship of the luminescent parent homometallic coordination polymers (Φem = 0.65 and 0.72 for the solid Cu and Ag polymers, respectively, at room temperature). The mixed-metallic polymer with the mole fraction of copper even as low as 0.005 exhibits a strong emission (Φem = 0.75) from only the copper sites as the result of the efficient energy migration from the silver to the copper sites. The migration rates between the two sites were evaluated from the dependence of emission decays upon the mole fraction of copper. [ABSTRACT FROM AUTHOR]

Background: Cytogenomic mutations and chromosomal abnormality are implicated in the neuropathology of several brain diseases. Cell heterogeneity of brain tissues makes their detection and validation difficult, however. In the present study, we analyzed gene dosage alterations in brain DNA of schizophrenia patients and compared those with the copy number variations (CNVs) identified in schizophrenia patients as well as with those in Asian lymphocyte DNA and attempted to obtain hints at the pathological contribution of cytogenomic instability to schizophrenia. Results: Brain DNA was extracted from postmortem striatum of schizophrenia patients and control subjects (n = 48 each) and subjected to the direct two color microarray analysis that limits technical data variations. Disease-associated biases of relative DNA doses were statistically analyzed with Bonferroni's compensation on the premise of brain cell mosaicism. We found that the relative gene dosage of 85 regions significantly varied among a million of probe sites. In the candidate CNV regions, 26 regions had no overlaps with the common CNVs found in Asian populations and included the genes (i.e., ANTXRL, CHST9, DNM3, NDST3, SDK1, STRC, SKY) that are associated with schizophrenia and/or other psychiatric diseases. The majority of these candidate CNVs exhibited high statistical probabilities but their signal differences in gene dosage were less than 1.5-fold. For test evaluation, we rather selected the 10 candidate CNV regions that exhibited higher aberration scores or larger global effects and were thus confirmable by PCR. Quantitative PCR verified the loss of gene dosage at two loci (1p36.21 and 1p13.3) and confirmed the global variation of the copy number distributions at two loci (11p15.4 and 13q21.1), both indicating the utility of the present strategy. These test loci, however, exhibited the same somatic CNV patterns in the other brain region. Conclusions: The present study lists the candidate regions potentially representing cytogenomic CNVs in the brain of schizophrenia patients, although the significant but modest alterations in their brain genome doses largely remain to be characterized further. [ABSTRACT FROM AUTHOR]

A [Ru(phen)3]2+ complex (phen = 1,10-phenanthroline) having an arylethynyl group at the 4-position of one of the three phen ligands (aryl: (dimesityl)borylduryl group = [RuBE]2+ or duryl group = [RuDE]2+) showed dual emissions at low temperature in propylene carbonate (PC). The shorter emission lifetime components (τem(s) ≈ 13 μs) that originated from the lowest-energy excited triplet states (T1) of the complexes were almost independent of temperature (T = 77-320 K), while the longer emission lifetime components (τem(l)), as the T2 emissions appeared below the fluid-to-glass transition temperature (Tg ≈ 220 K) in PC, were almost constant at 27 μs in the range of T = 77-220 K. The τem(s) components of the complexes were assigned to the emissions from the metal-to-ligand charge transfer (MLCT) excited states possessing relatively large ligand-centered (LC) excited-state characters (T1(MLCT/LC)), while the τem(l) components were shown to be originating from the T2(MLCT) excited states. The T2(MLCT) states of the complexes became nonemissive above Tg in PC due to fast nonradiative decay through solvent reorganization around the T2(MLCT) excited states. The photophysical properties of the complexes were also shown to be characterized by the presence of the arylethynyl units at the 4-positions of the phen ligands. [ABSTRACT FROM AUTHOR]

The hexarhenium cluster complexes with benzotriazolate apical ligands [{Re6(μ3-Q)8}(BTA)6]4- (Q = S, Se; BTA = benzotriazolate ion) were obtained by the reaction of [{Re6(μ3-Q)8}(OH)6]4- with molten 1H-BTA (1H-benzotriazole). The clusters were crystallized as potassium salts and characterized by X-ray single-crystal diffraction, elemental analyses, and UV-vis and luminescence spectroscopy. In addition, their cellular uptake and toxicity were evaluated. It was found that both clusters exhibited luminescence with high lifetimes and quantum yield values; they were taken up by the cells illuminating them under UV irradiation and, at the same time, did not exhibit acute cytotoxic effects. [ABSTRACT FROM AUTHOR]

Solvent effects on the spectroscopic and photophysical properties of tris{[p-(N,N-dimethylamino)phenylethynyl]duryl}borane (TMAB) and tris[(phenylethynyl)duryl]borane (TPhB) were studied in detail. Both TMABand TPhBexhibited broad and structureless absorption and fluorescence bands ascribed to the charge transfer (CT) transition between the π-orbital of the aryl group (π(aryl)) and the vacant p-orbital on the boron atom (p(B)): π(aryl)-p(B) CT. The fluorescence spectra of TMABand TPhBwere dependent on a solvent polarity, and the Stokes shifts of the compounds (ΔνS) were shown to correlate linearly with a solvent polarity parameter: f(X) = (Ds− 1)/(2Ds 1) − (n2− 1)/(2n2 1) where Dsand nare the dielectric constant and refractive index of a solvent, respectively. The slope value of the ΔνSversus f(X) plot gave the excited singlet state dipole moment of TMABor TPhBto be ∼60 or ∼30 D, respectively, demonstrating that the excited singlet state of TMABpossessed an extremely large dipole moment. The fluorescence quantum yields (Φf) and lifetimes (τf) of the compounds were also dependent on f(X). Detailed analysis of the present results demonstrated that the photophysical properties of TMABwere governed by the magnitude of the fluorescence rate constant (kf) and the kfvalue decreased almost one-tenth with an increase in f(X), which was the primary origin of the f(X) dependences of Φfand τf. The results were discussed in terms of the characteristic π(aryl)-p(B) CT excited states of the derivatives. [ABSTRACT FROM AUTHOR]

Poly(N-isopropylacrylamide) and poly(vinyl methyl ether) are well-known thermoresponsive polymers. The aqueous solutions of these polymers exhibit a phase transition followed by phase separation with LCST ∼ 305−310 K. In the present study, the dynamic behavior of the phase separation was analyzed by a laser T-jump method. Two different T-jump methodologies were employed:  the first was a dye-photosensitized T-jump technique (indirect heating) using 532 nm laser pulses, while the other was a direct heating T-jump technique using 1.2 m laser pulses. Both methods gave similar results. The time constants () of the phase separation were systematically determined for 1−10 wt % aqueous solutions of the polymers, and a hydrodynamic radius (R) dependence for was clearly observed. The values of increased linearly with increasing square of R. The present behavior is interpretable in the framework of Tanaka's model for the volume phase transition of a gel, since each of the polymer chains are entangled in the present sample solutions, which can be regarded as approximating to a gel in solution. [ABSTRACT FROM AUTHOR]

The direction of excitation energy migration is reversed in a system composed of {Ru(bpy)2}-{pyridylporphyrin}2 by the addition of a Zn2+ ion. The Zn2+ system shows an excitation-wavelength dependent emission. [ABSTRACT FROM AUTHOR]