Theoretical insight on the electronic structure and photophysical properties of three blue cyclometalated Ir(III) complexes based on the benchmark complex FIrpic

The electronic and photophysical properties of three blue cyclometalated Ir(III) complexes have been investigated by using the density functional theory (DFT) and time dependent density functional theory (TDDFT) methods. Both HOMO and LUMO values of complexes 1, 2 and 3 are in the order of 1 > 2 > 3. The lowest-lying singlet absorption for 1, 2 and three attributed to the configurations of the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO) with the d(Ir)+π(A)→π*(A) [MLCT/ILCT] character. Complexes 1, 2 and three possess almost the same phosphorescence wavelength and transition characters.</p

BV/TV

the raw data of BV/T

Passive Air Sampling of Organochlorine Pesticides, Polychlorinated Biphenyls, and Polybrominated Diphenyl Ethers Across the Tibetan Plateau

So far there are limited data on persistent organic pollutants (POPs) in the atmosphere of the Tibetan Plateau. XAD 2-resin based passive air samplers were therefore deployed for 1 year (between July 2007-June 2008) at 16 locations across the Tibetan Plateau. Based on previously reported sampling rates (R) derived in the north and south America, and their correlations with atmospheric temperature and pressure, R values in the present study were in the range of 2.2−3.3 m3 d−1 (average = 2.7 ± 0.3). Derived air concentrations (pg/m3) ranged as follows: DDTs, 5−75; HCHs, 0.1−36; α-endosulfan, 0.1−10; HCB, 2.8−80; sum of 15 PCBs, 1.8−8.2; and sum of 9 PBDEs, 0.1−8.3. The highest DDTs occurred at Qamdo, where the sampling site is near to farm land, indicating the spatial distribution of DDTs across the plateau may be influenced by scattered local usage of DDT. Higher levels of HCHs were observed at sites with high elevation (>4000 m) and close to the China-India border, indicating possible long-range atmospheric transport. The highest levels of HCB, PCBs, and PBDEs were found at a site impacted by forest fire during the sampling campaign

TBSP

the raw data of TB.S

Characterization of Tibetan Soil As a Source or Sink of Atmospheric Persistent Organic Pollutants: Seasonal Shift and Impact of Global Warming

Background soils are reservoirs of persistent organic pollutants (POPs). After decades of reduced primary emissions, it is now possible that the POPs contained in these reservoirs are being remobilized because of climate warming. However, a comprehensive investigation into the remobilization of POPs from background soil on the largest and highest plateau on Earth, the Tibetan Plateau (TP), is lacking. In this study, a sampling campaign was carried out on the TP at three background sites with different land cover types (forest, meadow and desert). Field measurements of the air–soil exchange of POPs showed that previous prediction using empirical models overestimated the values of the soil–air partitioning coefficient (KSA), especially for chemicals with KOA > 9. The direction of exchange for γ-HCH, HCB, and PCB-28 overlapped with the air–soil equilibrium range, but with a tendency for volatilization. Their emission fluxes were 720, 2935, and 538 pg m–2 day–1, respectively, and were similar in extent to those observed for background Arctic soil in Norway. Nam Co and Ngari are also permafrost regions, and most chemicals at these two sites exhibited volatilization. This is the first result showing that permafrost can also emit POPs. Seasonally, we found that chemicals tended to be re-emitted from soils to the atmosphere in winter and deposited from the air to the soil in summer. This finding is opposite to most previous results, possibly because of the higher air–soil concentration gradient caused by the prevailing transport of POPs in summer. Climate warming exerts a strong influence on air–soil exchange, with an increase of 1 °C in ambient temperature likely leading to an increase of Tibetan atmospheric inventories of POPs by 60–400%

Morpholino Monolayers: Preparation and Label-free DNA Analysis by Surface Hybridization

Surface hybridization, a reaction in which nucleic acid molecules in solution react with nucleic acid partners immobilized on a surface, is widely practiced in life science research. In these applications the immobilized partner, or “probe”, is typically single-stranded DNA. Because DNA is strongly charged, high salt conditions are required to enable binding between analyte nucleic acids (“targets”) in solution and the DNA probes. High salt, however, compromises prospects for label-free monitoring or control of the hybridization reaction through surface electric fields; it also stabilizes secondary structure in target species that can interfere with probe−target recognition. In this work, initial steps toward addressing these challenges are taken by introducing morpholinos, a class of uncharged DNA analogues, for surface-hybridization applications. Monolayers of morpholino probes on gold supports can be fabricated with methods similar to those employed with DNA and are shown to hybridize efficiently and sequence-specifically with target strands. Hybridization-induced changes in the interfacial charge organization are analyzed with electrochemical methods and compared for morpholino and DNA probe monolayers. Molecular mechanisms connecting surface hybridization state to the interfacial capacitance are identified and interpreted through comparison to numerical Poisson−Boltzmann calculations. Interestingly, positive as well as negative capacitive responses (contrast inversion) to hybridization are possible, depending on surface populations of mobile ions as controlled by the applied potential. Quantitative comparison of surface capacitance with target coverage (targets/area) reveals a nearly linear relationship and demonstrates sensitivities (limits of quantification) in the picogram per square millimeter range

BIC

the raw data of BI

Chemical Protein Polyubiquitination Reveals the Role of a Noncanonical Polyubiquitin Chain in DNA Damage Tolerance

Polyubiquitination of proteins regulates a variety of cellular processes, including protein degradation, NF-κB pathway activation, apoptosis, and DNA damage tolerance. Methods for generating polyubiquitinated protein with defined ubiquitin chain linkage and length are needed for an in-depth molecular understanding of protein polyubiquitination. However, enzymatic protein polyubiquitination usually generates polyubiquitinated proteins with mixed chain lengths in a low yield. We report herein a new chemical approach for protein polyubiquitination with a defined ubiquitin chain length and linkage under a mild condition that preserves the native fold of the target protein. In DNA damage tolerance, K63-polyubiquitinated proliferating cell nuclear antigen (PCNA) plays an important yet unclear role in regulating the selection of the error-free over error-prone lesion bypass pathways. Using the chemically polyubiquitinated PCNA, we revealed a mechanism of the K63 polyubiquitin chain on PCNA in promoting the error-free lesion bypass by suppressing the DNA translesion synthesis (TLS)

Transient Kinetic Analysis of USP2-Catalyzed Deubiquitination Reveals a Conformational Rearrangement in the K48-Linked Diubiquitin Substrate

Deubiquitination has emerged as an essential regulatory mechanism of a number of cellular processes. An in-depth understanding of deubiquitinating enzyme (DUB) catalysis, particularly the mode of ubiquitin binding and the individual steps in the DUB catalytic turnover, is imperative for exploiting DUBs for therapeutic intervention. In this work, we present a transient kinetic study of USP2 in hydrolyzing a model substrate Ub-AMC and a physiological substrate K48-linked diubiquitin. We conducted stopped-flow fluorescence analyses of the binding of mono- and diubiquitin to an inactive USP2 mutant and unveiled interesting differences in the binding kinetics between the two substrates. While a simple one-step binding of monoubiquitin to USP2 was observed, a biphasic binding was evident for diubiquitin. We further followed the deubiquitination reaction of Ub-AMC and K48-linked IQF-diubiquitin by USP2 using stopped-flow florescence under a single-turnover condition. Global fitting of the reaction traces revealed differences in the microscopic rate constants between Ub-AMC and the physiological diubiquitin substrate. Our binding and single-turnover data support a conformational rearrangement of the diubiquitin substrate in USP2-catalyzed deubiquitination. This finding is significant given the recent finding that the K48-linked diubiquitin is dynamic in its conformation. Our results provide useful insights into the mechanism of how USP recognizes ubiquitin moieties in a chain structure, which is important for understanding USP catalysis and developing inhibitors against USPs

Stereoselective Total Synthesis of (−)-Perrottetinene and Assignment of Its Absolute Configuration

The first stereoselective total synthesis of the bibenzyl tetrahydrocannabinol, (−)-perrottetinene, has been achieved from readily available starting materials. The absolute stereochemistry is derived from a chiral γ-hydroxy vinylstannane. The key reaction is the synthesis of the cis-disubstituted cyclohexene ring of perrottetinene by diastereoselective Ireland−Claisen rearrangement and a ring-closing metathesis reaction. The absolute configuration of (−)-perrottetinene is proposed