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61.
The directional energy transport, i.e. exciton migration, in nanostar dendritic systems composed of two-state monomer units is studied using a quantum master equation approach. We examine the effects of the variation in the excitation energy of the monomer in the core region (core monomer) on the multistep exciton migration from the periphery to the core based on the relaxation factors among exciton states originating in weak exciton-phonon coupling. It turns out that when the core monomer possesses both an excitation energy slightly lower than that of the first generation and a partial exciton overlap with the first generation, more efficient and rapid exciton migration to the core is expected as compared with other core monomer cases with the energy level closer to or much lower than that of the first generation. 相似文献
62.
Let a set {Xλ; λ Λ} of subspaces of a topological space X be a cover of X. Mathematical conditions are proposed for each subspace Xλ to define a map gXλ:Xλ→X which has the following property specific to the tent map known in the baker’s transformation. Namely, for any infinite sequence ω0, ω1, ω2, … of Xλ, λ Λ, we can find an initial point x0 ω0 such that gω0(x0)ω1,gω1(gω0(x0))ω2,…. The conditions are successfully applied to a closed cover of a weak self-similar set. 相似文献
63.
Lars Lauterbach Hongxin Wang Marius Horch Leland B. Gee Yoshitaka Yoda Yoshihito Tanaka Ingo Zebger Oliver Lenz Stephen P. Cramer 《Chemical science》2015,6(2):1055-1060
Hydrogenases are complex metalloenzymes that catalyze the reversible splitting of molecular hydrogen into protons and electrons essentially without overpotential. The NAD+-reducing soluble hydrogenase (SH) from Ralstonia eutropha is capable of H2 conversion even in the presence of usually toxic dioxygen. The molecular details of the underlying reactions are largely unknown, mainly because of limited knowledge of the structure and function of the various metal cofactors present in the enzyme. Here, all iron-containing cofactors of the SH were investigated by 57Fe specific nuclear resonance vibrational spectroscopy (NRVS). Our data provide experimental evidence for one [2Fe2S] center and four [4Fe4S] clusters, which is consistent with the amino acid sequence composition. Only the [2Fe2S] cluster and one of the four [4Fe4S] clusters were reduced upon incubation of the SH with NADH. This finding explains the discrepancy between the large number of FeS clusters and the small amount of FeS cluster-related signals as detected by electron paramagnetic resonance spectroscopic analysis of several NAD+-reducing hydrogenases. For the first time, Fe–CO and Fe–CN modes derived from the [NiFe] active site could be distinguished by NRVS through selective 13C labeling of the CO ligand. This strategy also revealed the molecular coordinates that dominate the individual Fe–CO modes. The present approach explores the complex vibrational signature of the Fe–S clusters and the hydrogenase active site, thereby showing that NRVS represents a powerful tool for the elucidation of complex biocatalysts containing multiple cofactors. 相似文献
64.
65.
Synthetic hydrogels can be used as scaffolds that not only favor endothelial cells(ECs) proliferation but also manipulate the behaviors and functions of the ECs.In this review paper,the effect of chemical structure,Young’s modulus (E) and zeta potential(ξ) of synthetic hydrogel scaffolds on static cell behaviors,including cell morphology,proliferation, cytoskeleton structure and focal adhesion,and on dynamic cell behaviors,including migration velocity and morphology oscillation,as well as on EC function such as anti-platelet adhesion,are reported.It was found that negatively charged hydrogels,poly(2-acrylamido-2-methylpropanesulfonic sodium)(PNaAMPS) and poly(sodium p-styrene sulphonate) (PNaSS),can directly promote cell proliferation,with no need of surface modification by any cell-adhesive proteins or peptides at the environment of serum-containing medium.In addition,the Young’s modulus(E) and zeta potential(ξ) of hydrogel scaffolds are quantitatively tuned by copolymer hydrogels,poly(NaAMPS-co-DMAAm) and poly(NaSS-co-DMAAm), in which the two kinds of negatively charged monomers NaAMPS and NaSS are copolymerized with neutral monomer,N,N-dimethylacrylamide(DMAAm).It was found that the critical zeta potential of hydrogels manipulating EC morphology,proliferation,and motility isξcritical= -20.83 mV andξcritical= -14.0 mV for poly(NaAMPS-co-DMAAm) and poly(NaSS-co-DMAAm),respectively.The above mentioned EC behaviors well correlate with the adsorption of fibronectin, a kind of cell-adhesive protein,on the hydrogel surfaces.Furthermore,adhered platelets on the EC monolayers cultured on the hydrogel scaffolds obviously decreases with an increase of the Young’s modulus(E) of the hydrogels,especially when E>60 kPa.Glycocalyx assay and gene expression of ECs demonstrate that the anti-platelet adhesion well correlates with the EC-specific glycocalyx.The above investigation suggests that understanding the relationship between physic-chemical properties of synthetic hydrogels and cell responses is essential to design optimal soft and wet scaffolds for tissue engineering. 相似文献
66.
Touge T Hakamata T Nara H Kobayashi T Sayo N Saito T Kayaki Y Ikariya T 《Journal of the American Chemical Society》2011,133(38):14960-14963
Newly developed oxo-tethered Ru amido complexes (R,R)-1 and their HCl adducts (R,R)-2 exhibited excellent catalytic performance for both asymmetric transfer hydrogenation and the hydrogenation of ketonic substrates under neutral conditions without any cocatalysts to give chiral secondary alcohols with high levels of enantioselectivity. 相似文献
67.
Nakano M Kishi R Yoneda K Inoue Y Inui T Shigeta Y Kubo T Champagne B 《The journal of physical chemistry. A》2011,115(31):8767-8777
The third-order nonlinear optical (NLO) properties, at the molecular level, the static second hyperpolarizabilities, γ, of supermolecular systems composed of phenalenyl and pyrene rings linked by acetylene units are investigated by employing the long-range corrected spin-unrestricted density functional theory, LC-UBLYP, method. The phenalenyl based superethylene, superallyl, and superbutadiene in their lowest spin states have intermediate diradical characters and exhibit larger γ values than the closed-shell pyrene based superpolyene systems. The introduction of a positive charge into the phenalenyl based superallyl radical changes the sign of γ and enhances its amplitude by a factor of 35. Although such sign inversion is also observed in the allyl radical and cation systems in their ground state equilibrium geometries, the relative amplitude of γ is much different, that is, |γ(regular allyl cation)/γ(regular allyl radical)| = 0.61 versus |γ(phenalenyl based superallyl cation)/γ(phenalenyl based superallyl radical)| = 35. In contrast, the model ethylene, allyl radical/cation, and butadiene systems with stretched carbon-carbon bond lengths (2.0 ?), having intermediate diradical characters, exhibit similar γ features to those of the phenalenyl based superpolyene systems. This exemplifies that the size dependence of γ as well as its sign change by introducing a positive charge on the phenalenyl based superpolyene systems originate from their intermediate diradical characters. In addition, the change from the lowest to the highest π-electron spin states significantly reduces the γ amplitudes of the neutral phenalenyl based superpolyene systems. For phenalenyl based superallyl cation, the sign inversion of γ (from negative to positive) is observed upon switching between the singlet and triplet states, which is predicted to be associated with a modification of the balance between the positive and negative contributions to γ. The present study paves the way toward designing a variety of open-shell NLO supermolecular systems composed of phenalenyl radical building blocks. 相似文献
68.
Kaname Ohyama Kana Oyamada Naoya Kishikawa Mitsuhiro Wada Yoshihito Ohba Kenichiro Nakashima Naotaka Kuroda 《Chromatographia》2011,74(5-6):467-470
Characteristics of the chiral stationary phase with poly(l-phenylalanine) peptide selector, which was in ??-helical state, was reported. Since environmental factors affect peptide conformation, the changes in enantioselectivity were examined depending on column temperature and mobile phase conditions (ionic strength, pH, mobile phase composition). Column temperature and pH drastically affected the enantioselectivity. Based on these changes, the relation between chiral recognition and secondary structure of the peptide selector was discussed. The column stability during sequential analysis under different separation conditions was also evaluated. 相似文献
69.
Shiraishi T Kitamura Y Ueno Y Kitade Y 《Chemical communications (Cambridge, England)》2011,47(9):2691-2693
We synthesised aryl acetylene derivatives as versatile probes for labelling of oligonucleotides. RNA oligomers bearing an aryl acetylene molecule rapidly reacted with benzylazide derivatives under ligand-free click reaction conditions. 相似文献
70.
Kidera M Seto Y Takahashi K Enomoto S Kishi S Makita M Nagamatsu T Tanaka T Toda M 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,78(3):1215-1219
We developed a detection technology for vapor forms of chemical warfare agents (CWAs) with an element analysis system using an electron cyclotron resonance ion source. After the vapor sample was introduced directly into the ion source, the molecular material was decomposed into elements using electron cyclotron resonance plasma and ionized. The following CWAs and stimulants were examined: diisopropyl fluorophosphonate (DFP), 2-chloroethylethylsulfide (2CEES), cyanogen chloride (CNCl), and hydrogen cyanide (HCN). The type of chemical warfare agents, specifically, whether it was a nerve agent, blister agent, blood agent, or choking agent, could be determined by measuring the quantities of the monatomic ions or CN(+) using mass spectrometry. It was possible to detect gaseous CWAs that could not be detected by a conventional mass spectrometer. The distribution of electron temperature in the plasma could be closely controlled by adjusting the input power of the microwaves used to generate the electron cyclotron resonance plasma, and the target compounds could be detected as molecular ions or fragment ions, enabling identification of the target agents. 相似文献