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631.
Rani-Beeram S Meyer K McCrate A Hong Y Nielsen M Swavey S 《Inorganic chemistry》2008,47(23):11278-11283
When the new porphyrin 5,10-(4-pyridyl)-15,20-(pentafluorophenyl)porphyrin is reacted with 2 equiv of Ru(bipy)(2)Cl(2) (where bipy = 2,2'-bipyridine) formation of the target ruthenated porphyrin is achieved with 40% yield. Strong electronic transitions are observed in the visible region of the spectrum associated with the porphyrin Soret and four Q-bands. A shoulder at slightly higher energy than the Soret band is attributed to the Ru(dpi) to bipy(pi*) metal to ligand charge transfer (MLCT) band. The bipyridyl pi to pi* transition occurs at 295 nm. Cyclic voltammetry experiments reveal two single-electron redox couples in the cathodic region at E(1/2) = -0.80 and -1.18 V vs Ag/AgCl associated with the porphyrin. Two overlapping redox couples at E(1/2) = 0.83 V vs Ag/AgCl due to the Ru(III/II) centers is also observed. DNA titrations using calf thymus (CT) DNA and the ruthenium porphyrin give a K(b) = 7.6 x 10(5) M(-1) indicating a strong interaction between complex and DNA. When aqueous solutions of supercoiled DNA and ruthenium porphyrin are irradiated with visible light (energy lower than 400 nm), complete nicking of the DNA is observed. Cell studies show that the ruthenated porphyrin is more toxic to melanoma skin cells than to normal fibroblast cells. When irradiated with a 60 W tungsten lamp, the ruthenium porphyrin preferentially leads to apoptosis of the melanoma cells over the normal skin cells. 相似文献
632.
Intramolecular arylation of benzimidazoles via Pd(II)/Cu(I) catalyzed cross-dehydrogenative coupling
Electron poor benzimidazole substrates were arylated via an intramolecular cross-dehydrogenative coupling (CDC) reaction. These CDC reactions were catalyzed by a Pd(II)/Cu(I) catalyst system, capable of producing moderate yields on a large library of substrates. The substrate scope consisted of tethered arene-benzimidazoles that upon coupling, produced a fused polycyclic motif. 相似文献
633.
Peng Wang Chang‐xin Huo Shuyao Lang Kyle Caution Setare Tahmasebi Nick Purnima Dubey Rajendar Deora Xuefei Huang 《Angewandte Chemie (International ed. in English)》2020,59(16):6451-6458
With the infection rate of Bordetella pertussis at a 60‐year high, there is an urgent need for new anti‐pertussis vaccines. The lipopolysaccharide (LPS) of B. pertussis is an attractive antigen for vaccine development. With the presence of multiple rare sugars and unusual glycosyl linkages, the B. pertussis LPS is a highly challenging synthetic target. In this work, aided by molecular dynamics simulation and modeling, a pertussis‐LPS‐like pentasaccharide was chemically synthesized for the first time. The pentasaccharide was conjugated with a powerful carrier, bacteriophage Qβ, as a vaccine candidate. Immunization of mice with the conjugate induced robust anti‐glycan IgG responses with IgG titers reaching several million enzyme‐linked immunosorbent assay (ELISA) units. The antibodies generated were long lasting and boostable and could recognize multiple clinical strains of B. pertussis, highlighting the potential of Qβ‐glycan as a new anti‐pertussis vaccine. 相似文献
634.
Roberto M. Tovar Kyle P. Johnson Keith Ashline Jorge M. Seminario 《International journal of quantum chemistry》2008,108(9):1546-1554
The current–voltage characteristics of small aliphatic chains of alkanes, alkenes, alkynes, and oligophenylene‐ethylenes, with and without substituents and terminated in sulfur attached nanosized gold electrodes are determined using ab initio procedures for discrete and extended systems in a density functional theory‐Green function's approach where most of the chemistry is considered. It is found that the current–voltage characteristics of small molecules can be tailored by the addition of substituents. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 相似文献
635.
We report the real-time and label-free detection of direct disaccharide binding to a lectin using a differential surface plasmon resonance detection method that allows for measurement of nanomolar concentrations of disaccharides. 相似文献
636.
Millimeter-sized gel particles loaded with camphor and floating at the interface between water and air generate convective flows around them. These flows give rise to repulsive interparticle interactions, and mediate dynamic self-assembly of nonequilibrium particle formations. When the numbers of particles, N, are small, particle motions are uncorrelated. When, however, N exceeds a threshold value, particles organize into ordered lattices. The nature of hydrodynamic forces underlying these effects and the dynamics of the self-assembling system are modeled numerically using Navier-Stokes equations as well as analytically using scaling arguments. 相似文献
637.
When we study the architecture of networks of spatially extended systems the nodes in the network are subject to local correlation structures. In this case, we show that for scale-free networks the traditional way to estimate the clustering coefficient may not be meaningful. Here we explain why and propose an approach that corrects this problem. 相似文献
638.
David J. Kyle Charles J. Arntzen Fabrice Franck† Y. Inoue 《Photochemistry and photobiology》1983,38(5):609-614
Abstract— Light-induced quenching of the low temperature fluorescence emission from photosystem II (PS II) at 695 nm ( F 695 ) has been observed in chloroplasts and whole leaves of spinach. Photosystem I (PS I) fluorescence emission at 735 nm ( F 735 ) is quenched to a lesser degree but this quenching is thought to originate from PS II and is manifest in a reduced amount of excitation energy available for spillover to PS I. Differential quenching of these two fluorescence emissions leads to an increase in the F 735 / F 685 ratio on exposure to light at 77 K. Rewarming the sample from -196°C discharges the thermoluminescence Z-band and much of the original unquenched fluorescence is recovered. The relationship between the thermoluminescence Z-band and the quenching of the low temperature fluorescence emission ( F 695 ) is discussed with respect to the formation of reduced pheophytin in the PS II reaction center at 77 K. 相似文献
639.
Crabtree KN Kauffman CA Tom BA Beçka E McGuire BA McCall BJ 《The Journal of chemical physics》2011,134(19):194311
The nuclear spin dependence of the chemical reaction H(3)(+)+ H(2) → H(2)?+ H(3)(+) has been studied in a hollow cathode plasma cell. Multipass infrared direct absorption spectroscopy has been employed to monitor the populations of several low-energy rotational levels of ortho- and para-H(3)(+) (o-H(3)(+) and p-H(3)(+)) in hydrogenic plasmas of varying para-H(2) (p-H(2)) enrichment. The ratio of the rates of the proton hop (k(H)) and hydrogen exchange (k(E)) reactions α ≡ k(H)/k(E) is inferred from the observed p-H(3)(+) fraction as a function of p-H(2) fraction using steady-state chemical models. Measurements have been performed both in uncooled (T(kin) ~ 350 K) and in liquid-nitrogen-cooled (T(kin) ~ 135 K) plasmas, marking the first time this reaction has been studied at low temperature. The value of α has been found to decrease from 1.6 ± 0.1 at 350 K to 0.5 ± 0.1 at 135 K. 相似文献
640.
Agnieszka Litomska Dr. Keishi Ishida Dr. Kyle L. Dunbar Marco Boettger Dr. Sébastien Coyne Prof. Dr. Christian Hertweck 《Angewandte Chemie (International ed. in English)》2018,57(36):11574-11578
6‐Thioguanine (6TG) is a DNA‐targeting therapeutic used in the treatment of various cancers. While 6TG was rationally designed as a proof of concept for antimetabolite therapy, it is also a rare thioamide‐bearing bacterial natural product and critical virulence factor of Erwinia amylovorans, plant pathogens that cause fire blight. Through gene expression, biochemical assays, and mutational analyses, we identified a specialized bipartite enzyme system, consisting of an ATP‐dependent sulfur transferase (YcfA) and a sulfur‐mobilizing enzyme (YcfC), that is responsible for the peculiar oxygen‐by‐sulfur substitution found in the biosynthesis of 6TG. Mechanistic and phylogenetic studies revealed that YcfA‐mediated 6TG biosynthesis evolved from ancient tRNA modifications that support translational fidelity. The successful in vitro reconstitution of 6TG thioamidation showed that YcfA employs a specialized sulfur shuttle that markedly differs from universal RNA‐related systems. This study sheds light on underexplored enzymatic C?S bond formation in natural product biosynthesis. 相似文献