Yu Zhang
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Yu Zhang
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An Approach to Tetraphenylenes via Pd-Catalyzed C-H Functionalization.
Journal: Organic letters
May/5/2016
Description

Tetraphenylenes not only are theoretically and experimentally interesting but also have potential applications in a variety of fields such as materials science, supramolecular chemistry, and asymmetric catalysis. A facile and efficient approach is reported for the syntheis of tetraphenylene and its derivatives from 2-iodobiphenyls via Pd-catalyzed C-H activation. A range of substituted tetraphenylenes can be synthesized using this method, and the reaction can be performed on gram scale with relatively high efficiency, demonstrating its practical utility. This novel approach provides easy access to tetraphenylenes and should facilitate research on the application of this type of fascinating molecules.

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Scanning Tunneling Microscopy of the π Magnetism of a Single Carbon Vacancy in Graphene.
Journal: Physical review letters
October/29/2016
Description

Pristine graphene is strongly diamagnetic. However, graphene with single carbon atom defects could exhibit paramagnetism. Theoretically, the π magnetism induced by the monovacancy in graphene is characteristic of two spin-split density-of-states (DOS) peaks close to the Dirac point. Since its prediction, many experiments have attempted to study this π magnetism in graphene, whereas only a notable resonance peak has been observed around the atomic defects, leaving the π magnetism experimentally elusive. Here, we report direct experimental evidence of π magnetism by using a scanning tunneling microscope. We demonstrate that the localized state of the atomic defects is split into two DOS peaks with energy separations of several tens of meV. Strong magnetic fields further increase the energy separations of the two spin-polarized peaks and lead to a Zeeman-like splitting. Unexpectedly, the effective g factor around the atomic defect is measured to be about 40, which is about 20 times larger than the g factor for electron spins.

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Fe(II)EDTA-NO reduction coupled with Fe(II)EDTA oxidation by a nitrate- and Fe(III)-reducing bacterium.
Journal: Bioresource technology
December/17/2013
Description

The nitrate- and Fe(III)-reducing bacterium Paracoccus versutus LYM was characterized in terms of its ability to perform Fe(II)EDTA-NO reduction coupled with Fe(II)EDTA oxidation (NO-dependent Fe(II)EDTA oxidation, NDFO). It experienced a single anaerobic FeEDTA redox cycling through NDFO and dissimilatory Fe(III)EDTA reduction in FeEDTA culture. The increase in the Fe(II)EDTA concentration contributed to the ascending Fe(II)EDTA-NO reduction rate. The amount of glucose controlled the rate and extent of Fe(II) oxidation during NDFO. Without glucose addition, Fe(II)EDTA-NO reduction rate was at a rather slow rate even in presence of relatively sufficient Fe(II)EDTA. Unlike aqueous Fe(2+) and solid-phase Fe(II), Fe(II)EDTA could prevent cells from encrustations. These findings suggested the occurrence of NDFO preferred being beneficial via a mixotrophic physiology in the presence of an organic cosubstrate to being out of consideration for metabolic strategy.

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Superparamagnetic anisotropic nano-assemblies with longer blood circulation in vivo: a highly efficient drug delivery carrier for leukemia therapy.
Journal: Nanoscale
October/7/2016
Description

Leukemia, unlike solid tumors, has no definite shape and spreads throughout the whole circulatory system, therefore the therapy of leukemia requires medication to stay longer in the circulatory system. Anisotropic nanoparticles, showing longer blood circulating life than that of isotropic nanoparticles reported in previous research, meet the demands of leukemia therapy. Based on this strategy, superparamagnetic anisotropic nano-assemblies (SANs) were fabricated and loaded with vincristine (VCR) to form VCR-SANs. When compared to the same dose of VCR-loaded isotropic nano-assemblies (SINs), the decrease in the leukocytes count and the positive expression ratio of CD13 in the VCR-SANs group were 19.38% and 16.4%, respectively, which indicated the improved anti-leukemia activity of the VCR-SANs. From the results of the pharmacokinetics study, the VCR-SANs remarkably held the amount of drug removed from the whole body per unit time half of the isotropic group and the concentration of drug in blood plasma against time was 2.1 times the isotropic group, demonstrating the rapid and sustained release behavior and longer blood circulation when combined with the results of in vivo tissue distribution studies. In summary, anisotropic nano-assemblies were found to be more promising than isotropic nano-assemblies via our in vivo and in vitro examinations.

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Micellar nanoparticle formation via electrostatic interactions for delivering multinuclear platinum(II) drugs.
Journal: Chemical communications (Cambridge, England)
November/11/2013
Description

Nanoparticles formed via electrostatic interactions between methoxy-polyethylene glycol-block-poly(glutamic acid) (MPEG-PGA) and a multinuclear platinum(II) drug, di-cisPt, exhibit efficient platinum loading, improved cellular uptake, in vitro cytotoxicity, and enhanced in vivo efficacy.

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Sepsis-Induced Thymic Atrophy Is Associated with Defects in Early Lymphopoiesis.
Journal: Stem cells (Dayton, Ohio)
November/23/2016
Description

Impaired T lymphopoiesis is associated with immunosuppression of the adaptive immune response and plays a role in the morbidity and mortality of patients and animal models of sepsis. Although previous studies examined several intrathymic mechanisms that negatively affect T lymphopoiesis, the extrathymic mechanisms remain poorly understood. Here, we report a dramatic decrease in the percentage of early T lineage progenitors (ETPs) in three models of sepsis in mice (cecal ligation and puncture, lipopolysaccharide continuous injection, and poly I:C continuous injection). However, septic mice did not show a decrease in the number of bone marrow (BM) precursor cells. Instead, the BM progenitors for ETPs expressed reduced mRNA levels of CC chemokine receptor (CCR) 7, CCR9 and P-selectin glycoprotein ligand 1, and exhibited impaired homing capacity in vitro and in vivo. Furthermore, RNA-Seq analysis and real-time PCR showed a marked downregulation of several lymphoid-related genes in hematopoietic stem and progenitor cells. Hematopoietic stem and progenitor cells differentiated into myeloid cells but failed to generate T lymphocytes in vitro and in vivo. Our results indicate that the depletion of ETPs in septic mice might be a consequence of an impaired migration of BM progenitors to the thymus, as well as a defect in lymphoid lineage commitment. Stem Cells 2016;34:2902-2915.

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Sirt1 protects pig oocyte against in vitro aging.
Journal: Animal science journal = Nihon chikusan Gakkaiho
August/10/2016
Description

Sirtuins have been widely reported to be involved in multiple biological processes. However, their function during pig oocyte aging has not been reported yet. Here, we first identify that sirt1 expression is dramatically reduced in pig in vitro-aged oocytes. Furthermore, by confocal scanning and quantitative analysis, we find the increased frequency of spindle defects and chromosome misalignment, disturbed redistribution of cortical granules and mitochondria during oocyte in vitro-aging. Importantly, these aging-associated defective phenotypes can be ameliorated through resveratrol (sirt1 activator) treatment during pig oocyte maturation, providing the evidence for the hypothesis that decreased sirt1 is one of a number of factors contributing to oocyte in vitro-aging. In summary, our data indicate a role for sirt1 in pig oocytes and uncover a striking beneficial effect of sirt1 expression on aged oocytes.

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Hydrogel patterning by diffusion through the matrix and subsequent light-triggered chemical immobilization.
Journal: ACS applied materials & interfaces
November/22/2015
Description

A novel approach to hyaluronic acid (HA) hydrogel with a chemical gradient of the matrix-linked bisphosphonate (BP) groups is presented. The method consists of two steps, including initial generation of physical gradient patterns of BPs by diffusion of BP acrylamide reagent into HA matrix carrying thiol groups and subsequent chemical immobilization of the BP groups by UV light-triggered thiol-ene addition reaction. This gradient hydrogel permits spatial three-dimensional regulation of secondary interactions of different molecules with the polymer matrix. In particular, graded amounts of cytochrome c (cyt c) were reversibly absorbed in the hydrogel, thus enabling the subsequent spatially controlled release of the therapeutic protein. The obtained patterned hydrogel acts also as a unique reactor in which peroxidase-catalyzed oxidation of a substrate is determined by spatial position of the enzyme (cyt c) in the matrix resulting in a range of product concentrations. As an example, matrix template-assisted oxidation of 3,3',5,5'-tetarmethylbenzydine (TMB) in the presence of H2O2 occurs simultaneously at different rates within the gradient hydrogel. Moreover, calcium binding to the gradient HABP hydrogel reflects the pattern of immobilized BP groups eventually leading to the graded biomineralization of the matrix. This approach opens new possibilities for use of hydrogels as dynamic models for biologic three-dimensional structures such as extracellular matrix.

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An ultrathin self-humidifying membrane for PEM fuel cell application: fabrication, characterization, and experimental analysis.
Journal: The journal of physical chemistry. B
September/9/2007
Description

An ultrathin poly(tetrafluoroethylene) (PTFE)-reinforced multilayer self-humidifying composite membrane (20 microm, thick) is developed. The membrane is composed of Nafion-impregnated porous PTFE composite as the central layer, and SiO2 supported nanosized Pt particles (Pt-SiO2) imbedded into the Nafion as the two side layers. The proton exchange membrane (PEM) fuel cell employing the self-humidifying membrane (Pt-SiO2/NP) turns out a peak power density of 1.40 W cm(-2) and an open circuit voltage (OCV) of 1.032 V under dry H2/O2 condition. The excellent performance is attributed to the combined result of both the accelerated water back-diffusion in the thin membrane and the adsorbing/releasing water properties of the Pt-SiO2 catalyst in the side layers. Moreover, the inclusion of the hygroscopic Pt-SiO2 catalyst inside the membrane results in an enhanced anode self-humidification capability and also the decreased cathode polarization (accordingly an improved cell OCV). Several techniques, such as transmission electronic microscopy, scanning electronic microscopy, energy dispersive spectroscopy, thermal analysis and electrochemical impedance spectroscopy etc., are employed to characterize the Pt-SiO2/NP membrane. The results are discussed in comparison with the plain Nafion/PTFE membrane (NP). It is established that the reverse net water drag (from the cathode to the anode) across the Pt-SiO2/NP membrane reaches 0.16 H2O/H+. This implies a good hydration of the Pt-SiO2/NP membrane and thus ensures an excellent PEM fuel cell performance under self-humidification operation.

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On the difference of the properties between the blue-shifting halogen bond and the blue-shifting hydrogen bond.
Journal: The journal of physical chemistry. A
September/23/2010
Description

The difference of the properties between the blue-shifting halogen bond and the blue-shifitng hydrogen bond has been investigated at the M06/6-311++G(d,p) theory level. It was found that the three lone electron pairs on the halogen atom play an important role for the difference of the properties between the blue-shifting halogen bond and the blue-shifitng hydrogen bond. The additional electron-density transfer from the three lone electron pairs on the halogen atom to the remote part of the halogen atom donor (i.e., the antibonding orbitals of the bonds other than X-Hal) makes the blue-shifting halogen bond much more ubiquitous in the halogen-bonded complexes than the blue-shifitng hydrogen bond in the hydrogen-bonded complexes, and it also makes the values of the X-Hal bond contraction generally much larger than the values of the X-H bond contraction. The difference of the properties between the X-Cl...Y blue-shifting halogen bond and the X-Br...Y blue-shifting halogen bond was also discussed.

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