The Unexpected and Exceptionally Facile Chemical Modification of the Phenolic Hydroxyl Group of Tyrosine by Polyhalogenated Quinones under Physiological Conditions

The phenolic hydroxyl group of tyrosine residue plays a crucial role in the structure and function of many proteins. However, little study has been reported about its modification by chemical agents under physiological conditions. In this study, we found, unexpectedly, that the phenolic hydroxyl group of tyrosine can be rapidly and efficiently modified by tetrafluoro-1,4-benzoquinone and other polyhalogenated quinones, which are the major genotoxic and carcinogenic quinoid metabolites of polyhalogenated aromatic compounds. The modification was found to be mainly due to the formation of a variety of fluoroquinone–<i>O</i>-tyrosine conjugates and their hydroxylated derivatives via nucleophilic substitution pathway. Analogous modifications were observed for tyrosine-containing peptides. Further studies showed that the blockade of the reactive phenolic hydroxyl group of tyrosine in the substrate peptide, even by very low concentration of tetrafluoro-1,4-benzoquinone, can prevent the kinase catalyzed tyrosine phosphorylation. This is the first report showing the exceptionally facile chemical modification of the phenolic hydroxyl group of tyrosine by polyhalogenated quinones under normal physiological conditions, which may have potential biological and toxicological implications

Implicit learning and emotional responses in nine-month-old infants

<p>To study the interplay between motor learning and emotional responses of young infants, we developed a contingent learning paradigm that included two related, difficult, operant tasks. We also coded facial expression to characterise emotional response to learning. In a sample of nine-month-old healthy Chinese infants, 44.7% achieved learning threshold during this challenging arm-conditioning test. Some evidence of learning was observed at the beginning of the second task. The lowest period of negative emotions coincided with the period of maximum movement responses after the initiation of the second task, and movement responses negatively correlated with the frequency of negative emotions. Positive emotions, while generally low throughout the task, increased during peak performance especially for learners. Peak frequency of movement responses was positively correlated with the frequency of positive emotions. Despite the weak evidence of learning this difficult task, our results from the learners would suggest that increasing positive emotions, and perhaps down-regulating negative emotional responses, may be important for improving performance and learning a complex operant task in infancy. Further studies are necessary to determine the role of emotions in learning difficult tasks in infancy.</p

Layer-by-Layer Polyelectrolyte Assisted Growth of 2D Ultrathin MoS₂ Nanosheets on Various 1D Carbons for Superior Li-Storage

Transitional metal sulfide/carbon hybrids with well-defined structures could not only maximize the functional properties of each constituent but engender some unique synergistic effects, holding great promise for applications in Li-ion batteries and supercapacitors and for catalysis. Herein, a facile and versatile approach is developed to controllably grow 2D ultrathin MoS₂ nanosheets with a large quantity of exposed edges onto various 1D carbons, including carbon nanotubes (CNTs), electrospun carbon nanofibers, and Te-nanowire-templated carbon nanofibers. The typical approach involves the employment of layer-by-layer (LBL) self-assembled polyelectrolyte, which controls spatially the uniform growth and orientation of ultrathin MoS₂ nanosheets on these 1D carbons irrespective of their surface properties. Such unique structures of the as-prepared CNTs@MoS₂ hybrid are significantly favorable for the fast diffusions of both Li-ions and electrons, satisfying the kinetic requirements of high-power lithium ion batteries. As a result, CNTs@MoS₂ hybrids exhibit excellent electrochemical performances for lithium storage, including a high reversible capacity (1027 mAh g^–1), high-rate capability (610 mAh g^–1 at 5 C), and excellent cycling stability (negligible capacity loss after 200 continuous cycles)

Mechanism of Intrinsic Chemiluminescence Production from the Degradation of Persistent Chlorinated Phenols by the Fenton System: A Structure–Activity Relationship Study and the Critical Role of Quinoid and Semiquinone Radical Intermediates

We found recently that intrinsic chemiluminescence (CL) could be produced by all 19 chlorophenolic persistent organic pollutants during environmentally friendly advanced oxidation processes. However, the underlying mechanism for the structure–activity relationship (SAR, i.e., the chemical structures and the CL generation) remains unclear. In this study, we found that, for all 19 chlorophenol congeners tested, the CL increased with an increasing number of chlorine atoms in general; and for chlorophenol isomers (such as the 6 trichlorophenols), the CL decreased in the order of meta- > ortho-/para-Cl-substituents with respect to the −OH group of chlorophenols. Further studies showed that not only chlorinated quinoid intermediates but also, more interestingly, chlorinated semiquinone radicals were produced during the degradation of trichlorophenols by the Fenton reagent; and the type and yield of which were determined by the directing effects, hydrogen bonding, and steric hindrance effect of the OH- and/or Cl-substitution groups. More importantly, a good correlation was observed between the formation of these quinoid intermediates and CL generation, which could fully explain the above SAR findings. This represents the first report on the structure–activity relationship study and the critical role of quinoid and semiquinone radical intermediates, which may have broad chemical and environmental implications for future studies on remediation of other halogenated persistent organic pollutants by advanced oxidation processes

Low-Temperature Reversible Hydrogen Storage Properties of LiBH₄: A Synergetic Effect of Nanoconfinement and Nanocatalysis

LiBH₄ has been loaded into a highly ordered mesoporous carbon scaffold containing dispersed NbF₅ nanoparticles to investigate the possible synergetic effect of nanoconfinement and nanocatalysis on the reversible hydrogen storage performance of LiBH₄. A careful study shows that the onset desorption temperature for nanoconfined LiBH₄@MC-NbF₅ system is reduced to 150 °C, 225 °C lower than that of the bulk LiBH₄. The activation energy of hydrogen desorption is reduced from 189.4 kJ mol^–1 for bulk LiBH₄ to 97.8 kJ mol^–1 for LiBH₄@MC-NbF₅ sample. Furthermore, rehydrogenation of LiBH₄ is achieved under mild conditions (200 °C and 60 bar of H₂). These results are attributed to the active Nb-containing species (NbH_<i>x</i> and NbB₂) and the function of F anions as well as the nanosized particles of LiBH₄ and high specific surface area of the MC scaffold. The combination of nanoconfinement and nanocatalysis may develop to become an important strategy within the nanotechnology for improving reversible hydrogen storage properties of various complex hydrides

Proliferation of colorectal cancer cells is mediated by both ErbB3/ErbB2 and ErbB3/c-MET signaling Pathways.

<p>(A) Detection of ErbB3, ErbB2 and c-MET in the human colorectal cancer cell lines LoVo, sw948 and sw480 by western-blot. (B, C, D) Cell viability measured by MTS assay in the colorectal cancer cell lines LoVo, sw948 and sw480 treated as indicated in the figure. The data are presented as mean ± SD, and *P<0.05, **P<0.01 by unpaired Student’s t test.</p

AKT and MAPK are the two cell signaling pathways governing viability of colorectal cancer cell lines with different receptor expression patterns.

<p>Differences in cell viability in LoVo (A, B) and SW948 (C, D) cells following treatment with different agonists or inhibitors, as indicated. The data are presented as mean±SD, and **P<0.01 by unpaired Student’s t test.</p

Low-Cost Synthesis of Hierarchical V₂O₅ Microspheres as High-Performance Cathode for Lithium-Ion Batteries

Hierarchical V₂O₅ microspheres composed of stacked platelets are fabricated through a facile, low-cost, and energy-saving approach. The preparation procedure involves a room-temperature precipitation of precursor microspheres in aqueous solution and subsequent calcination. Because of this unique structure, V₂O₅ microspheres manifest a high capacity (266 mA h g^–1), excellent rate capability (223 mA h g^–1 at a current density 2400 mA g^–1), and good cycling stability (200 mA h g^–1 after 100 cycles) as cathode materials for lithium-ion batteries

Activation of MAPK or AKT signaling in colorectal cancer cells with different molecular patterns of expression.

<p>(A, B) Detection of AKT and MAPK signaling in SW948 and LoVo cells by western-blot, with the treatment indicated in the figure. (C, D) Detection of AKT and MAPK signaling by western-blot in LoVo and SW948 cells with HGF or HRG1-β1 treatment, with or without different agonists or antagonists, as indicated.</p

Heterogeneous expression of ErbB3, ErbB2 and c-MET in human colorectal cancer.

<p>(A) Ratio of strong/moderate/weak/negative staining of ErbB3, ErbB2 and c-MET in human colorectal cancer. (B) Detection of ErbB3, ErbB2 and c-MET in protein extracted from tissue samples of 4 cases of colorectal cancer. (C) Venn diagram showing co-expression of ErbB3, ErbB2 and c-MET.</p