Complex Formation between the Lumenal Domain of Adenovirus E3–19k Protein and the Extracellular Domain of Class I MHC Molecule In Vitro

The Ad2 E3–19k protein inhibits the transport of newly synthesized class I MHC molecules to the cell surface, thereby interfering with antigen presentation. The details of the interaction between E3–19k protein and class I MHC molecules have not been well‐defined. In this present study, we describe the use of gel filtration HPLC for confirming the binding interaction of two domain proteins, E3–19k and MHC class I antigen, and subsequently the characterization of protein complex by SDS‐PAGE. Our results demonstrate the complex formation between Ad2 lumenal E3–19k (108 amino acids, wt 108) and HLA‐A*0201 molecule in vitro. Titration experiments will be employed in the future to determine stoichiometry and verify the specific interactions.     

Topological analysis and charge density studies of an alpha-diimine macrocyclic complex of cobalt(II)--a combined experimental and theoretical study

A combined experimental and theoretical study of the paramagnetic [Co(II)(C12H20N8)(H2O)2] x 2 ClO4 complex was made on the basis of the electron density distribution and topological analysis. Accurate single-crystal diffraction data were measured on a suitable crystal with Mo(K alpha) radiation at 125 K. The CoII ion is coordinated in a square bipyramidal fashion with four imino nitrogen atoms at the equatorial plane and two water molecules at the axial positions. The hydrogen-bonding interaction at 125 K between the coordinated water molecule and the ClO(4)(-) ion makes the space group different from that at 298 K. Parallel MO calculations were made at UHF and DFT/UB3LYP. The agreement between experiment and theory is reasonably good. The chemical bonding characterization is presented in terms of the topological properties associated with bond critical points and the natural bond orbital (NBO) analysis as well. The Co-N(imino) and Co-O(water) bonds are dative bonds, where the lone-pair electrons of N or O serve as a -donor; however, a certain covalent character is identified in the Co-N(imino) bond. A delocalized C-N, N-N pi-bond model is proposed. The d-orbital energies of Co in this complex are such that E(d(xz)) is approximately equal to E(d(yz)) is approximately equal to E(dx(2-y2)) < E(d(z2)) < E(d(xy)); notice that d(xy) and d(z2) are d(sigma) orbitals in this case. The Co(II) ion is in a low-spin d7 state with the singly occupied d(z2) orbital. The asphericity in electron density at Co and Cl nuclei is nicely demonstrated by the Laplacian of electron density. The envelope plot of the isovalue Laplacian surface around the nucleus gives the exact shape of such asphericity. The isovalue Laplacian surfaces of these two nuclei show significantly different VSCC character in both experimental and theoretical results.     

Direct and simultaneous determination of arsenic, manganese, cobalt and nickel in urine with a multielement graphite furnace atomic absorption spectrometer

A simple method was developed for the direct and simultaneous determination of arsenic (As), manganese (Mn), cobalt (Co), and nickel (Ni) in urine by a multi-element graphite furnace atomic absorption spectrometer (Perkin-Elmer SIMAA 6000) equipped with the transversely heated graphite atomizer and longitudinal Zeeman-effect background correction. Pd was used as the chemical modifier along with either the internal furnace gas or a internal furnace gas containing hydrogen and a double stage pyrolysis process. A standard reference material (SRM) of Seronorm™ Trace Elements in urine was used to confirm the accuracy of the method. The optimum conditions for the analysis of urine samples are pyrolysis at 1350 °C (using 5% H₂ v/v in Ar as the inter furnace gas during the first pyrolysis stage and pure Ar during the second pyrolysis stage) and atomization at 2100 °C. The use of Ar and matrix-free standards resulted in concentrations for all the analytes within 85% (As) to 110% (Ni) of the certified values. The recovery for As was improved when mixture of 5% H₂ and 95% Ar (v/v) internal furnace gas was applied during the first step of a two-stage pyrolysis at 1350 °C, and the found values of the analytes were within 91-110% of the certified value. The recoveries for real urine samples were in the range 88-95% for these four elements. The detection limits were 0.78 μg l⁻¹ for As, 0.054 μg l⁻¹ for Mn, 0.22 μg l⁻¹ for Co, and 0.35 μg l⁻¹ for Ni. The upper limits of the linear calibration curve are 60 μg l⁻¹ (As); 12 μg l⁻¹ (Mn); 12 μg l⁻¹ (Co) and 25 μg l⁻¹ (Ni), respectively. The relative standard deviations (R.S.D.s) for the analysis of SRM were 2% or less. The R.S.D.s of a real urine sample are 1.6% (As), 6.3% (Mn), 7.0% (Ni) and 8.0% (Co), respectively.     

Conflict in a changing climate

A growing body of research illuminates the role that changes in climate have had on violent conflict and social instability in the recent past. Across a diversity of contexts, high temperatures and irregular rainfall have been causally linked to a range of conflict outcomes. These findings can be paired with climate model output to generate projections of the impact future climate change may have on conflicts such as crime and civil war. However, there are large degrees of uncertainty in such projections, arising from (i) the statistical uncertainty involved in regression analysis, (ii) divergent climate model predictions, and (iii) the unknown ability of human societies to adapt to future climate change. In this article, we review the empirical evidence of the climate-conflict relationship, provide insight into the likely extent and feasibility of adaptation to climate change as it pertains to human conflict, and discuss new methods that can be used to provide projections that capture these three sources of uncertainty.     

Moenomycin Biosynthesis: Structure and Mechanism of Action of the Prenyltransferase MoeN5

The structure of MoeN5, a unique prenyltransferase involved in the biosynthesis of the antibiotic moenomycin, is reported. MoeN5 catalyzes the reaction of geranyl diphosphate (GPP) with the cis‐farnesyl group in phosphoglycolipid 5 to form the (C₂₅) moenocinyl‐sidechain‐containing lipid 7 . GPP binds to an allylic site (S1) and aligns well with known S1 inhibitors. Alkyl glycosides, glycolipids, can bind to both S1 and a second site, S2. Long sidechains in S2 are “bent” and co‐locate with the homoallylic substrate isopentenyl diphosphate in other prenyltransferases. These observations support a MoeN5 mechanism in which 5 binds to S2 with its C6–C11 group poised to attack C1 in GPP to form the moenocinyl sidechain, with the more distal regions of 5 aligning with the distal glucose in decyl maltoside. The results are of general interest because they provide the first structures of MoeN5 and a structural basis for its mechanism of action, results that will facilitate the design of new antibiotics.     

PtII Complexes with 6‐(5‐Trifluoromethyl‐Pyrazol‐3‐yl)‐2,2′‐Bipyridine Terdentate Chelating Ligands: Synthesis,Characterization, and Luminescent Properties

A series of Pt^II complexes Pt(fpbpy)Cl ( 1 ), Pt(fpbpy)(OAc) ( 2 ), Pt(fpbpy)(NHCOMe) ( 3 ), Pt(fpbpy)(NHCOEt) ( 4 ), and [Pt(fpbpy)(NCMe)](BF₄) ( 5 ) with deprotonated 6‐(5‐trifluoromethyl‐pyrazol‐3‐yl)‐2,2′‐bipyridine terdentate ligand are prepared, among which 1 is converted to complexes 2 – 5 by a simple ligand substitution. Alternatively, acetamide complex 3 is prepared by hydrolysis of acetonitrile complex 5 , while the back conversion from 3 to 1 is regulated by the addition of HCl solution, showing the reaction sequence 1 → 5 → 3 → 1 . Multilayer OLED devices are successfully fabricated by using triphenyl‐(4‐(9‐phenyl‐9H‐fluoren‐9‐yl)phenyl) silane (TPSi‐F) as host material and with doping concentrations of 1 varying from 7 to 100 %. The electroluminescence showed a substantial red‐shifting versus the normal photoluminescence detected in solution. Moreover, at a doping concentration of 28 %, the device showed a saturated red luminescence with a maximum external quantum yield of 8.5 % at 20 mA cm^?2 and a peak luminescence of 47 543 cd m^?2 at 18.5 V.     

Oligonucleotide-stabilized Ag nanocluster fluorophores

Single-stranded oligonucleotides stabilize highly fluorescent Ag nanoclusters, with emission colors tunable via DNA sequence. We utilized DNA microarrays to optimize these scaffold sequences for creating nearly spectrally pure Ag nanocluster fluorophores that are highly photostable and exhibit great buffer stability. Five different nanocluster emitters have been created with tunable emission from the blue to the near-IR and excellent photophysical properties. Ensemble and single molecule fluorescence studies show that oligonucleotide encapsulated Ag nanoclusters exhibit significantly greater photostability and higher emission rates than commonly used cyanine dyes.