Search results for "cyclic"

Dual Role of Vinyl Sulfonamides as N -Nucleophiles and Michael Acceptors in the Enantioselective Synthesis of Bicyclic δ-Sultams

2018

A peptide inhibiting the collagen binding function of integrin alpha2I domain.

1999

Integrin alpha2 subunit forms in the complex with the beta1 subunit a cell surface receptor binding extracellular matrix molecules, such as collagens and laminin-1. It is a receptor for echovirus-1, as well. Ligands are recognized by the special "inserted" domain (I domain) in the integrin alpha2 subunit. Venom from a pit viper, Bothrops jararaca, has been shown to inhibit the interaction of platelet alpha2beta1 integrin with collagen because of the action of a disintegrin/metalloproteinase named jararhagin. The finding that crude B. jararaca venom could prevent the binding of human recombinant ralpha2I domain to type I collagen led us to study jararhagin further. Synthetic peptides represe…

Crystal structure of human gamma-butyrobetaine hydroxylase.

2010

Gamma-butyrobetaine hydroxylase (GBBH) is a 2-ketoglutarate-dependent dioxygenase that catalyzes the biosynthesis of l-carnitine by hydroxylation of gamma-butyrobetaine (GBB). l-carnitine is required for the transport of long-chain fatty acids into mitochondria for generating metabolic energy. The only known synthetic inhibitor of GBBH is mildronate (3-(2,2,2-trimethylhydrazinium) propionate dihydrate), which is a non-hydroxylatable analog of GBB. To aid in the discovery of novel GBBH inhibitors by rational drug design, we have solved the three-dimensional structure of recombinant human GBBH at 2.0A resolution. The GBBH monomer consists of a catalytic double-stranded beta-helix (DBSH) domai…

2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents in extracts of Baltic white-tailed sea eagles

1997

Concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin-(TCDD) equivalents were measured in extracts of Baltic white-tailed sea eagle tissues. Extracts of salmon, ringed seal, and grey seal were analyzed as other predatory species of the same area. Concentrations in eagle and seal tissues were greater than those in salmon. Concentrations of TCDD equivalents (TCDD-EQs) determined by the H4IIE bioassay were compared with toxic equivalents (TEQs) derived from instrumental chemical analyses in fractions containing polychlorinated dibenzo-P-dioxins and polychlorinated dibenzofurans (PCDD/PCDF) or coplanar polychlorinated biphenyls (PCBs). Toxic equivalents were calculated by use of an additive mod…

Seismic behavior of exterior RC beam-column joints without code-specified ties in the joint core

2021

Abstract Beam-column joint design for reinforced concrete (RC) buildings is a critical issue for modern earthquake engineering, because for these structural elements, the current codes provide several geometrical constraints and reinforcement provisions, which may be very complex to implement during the construction phase. To investigate how a construction error might influence the joint behavior, two identical full-scale exterior beam-column joints specimens are built, according to Italian Building Code specifications for the high ductility class, but without the required horizontal ties inside the joint panel. This construction error could be plausible because, according to the design dra…

Two atropisomers of tricarbonyl[η6-7-chloro-3-(3-chloro-2-methylphenyl)-2,4,8-trimethyl-1,2,3,4-tetrahydro-2,4-dibora-1,3-diazanaphthalene]chromium(0)

2001

The structures of two atropisomers of the title compound, [Cr(C16H18B2Cl2N2)(CO)3], are reported. For both compounds, the Cr(CO)3 moiety is bound to the C6 aromatic ring of the mol­ecule; the existence of atropisomers resulting from the non-equivalence of both faces of the C6 aromatic ring is a consequence of the 3-chloro-2-methylphenyl ring being nearly perpendicular to the mean plane of the 2,4-dibora-1,3-di­aza­naphthalene ring. The orientation of the Cr(CO)3 tripod relative to the C6 aromatic ring is such that it is nearly eclipsed in one isomer (2.4° rotation from being eclipsed with C—N, C—Cl and C—H) and slightly twisted (16.2°) from an eclipsed conformation in the other.

Basel III: Countercyclical Capital Buffer Proposal-the Case of Baltics

2014

Abstract The objective of countercyclical capital buffer is to encourage banks to build up buffers in good times that can be drawn down in bad times. The aim of the report is to assess such decisions by banks derived from two approaches. The approaches are the aggregate credit-to-GDP ratio as well as credit growth. The approaches are implemented for Estonia, Latvia and Lithuania for the time period 2000–2012. The report compares two approaches and analyses their relevance to the Baltic states by testing the correlation between a growth in studied variables and a growth of corresponding gaps. Methods used in the empirical part of the report are econometric analysis as well as economic analys…

Thermal 1,6-Electrocyclization Reactions of Acceptor-Substituted 2,3-Divinyl-1H-indoles Yielding Functionalized Carbazoles

1990

Three new synthetic procedures for and thermal 1,6-electrocyclizations of acceptor-substituted 2,3-divinyl-1H-indoles leading to functionalizing carbazoles are described. The scope and limitations as well as some mechanistic aspects of the methodologies are discussed. The key strategies employed include Pd(II)-catalyzed coupling and Wittig procedures.

A comparative evaluation of palladium and platinum nanoparticles as catalysts in proton exchange membrane electrochemical cells

2008

The goal of the present study is the development and comparative characterisation of carbon-supported and nanostructured Pd- and Pt-based electrocatalysts for hydrogen oxidation in Proton Exchange Membrane (PEM) H2/O2(air) fuel cells and proton reduction in PEM water electrolysers. Catalysts have been synthesised in a solution using a combined impregnation/reduction polyol method. They have been characterised using X-ray Diffraction (XRD) analysis, Transmission Electron Microscopy (TEM), Thermogravimetric Analysis (TGA) and cyclic voltammetry. NanoPt, nanoPd and nanoPt-Pd catalysts deposited onto a carbon carrier have been used to prepare Membrane-Electrode Assemblies (MEAs) which, in turn,…

Experimental analysis of materials in proton exchange membrane electrolysis cells

2019

Abstract An accelerated supply and demand of energy has resulted in an increased need for efficient energy storage options, where storing energy in hydrogen gas emerges as one of the most attractive. In this study, a singular proton exchange membrane (PEM) electrolysis cell was designed using adequately low-cost materials, and tested using polarisation curves, cyclic voltammetry and AC impedance. A comparative study of various micro porous layer (MPL) materials was performed in an effort to find suitable options which are able to steadily operate under anodic conditions. The best performance was achieved using carbon cloth, however this material was unstable. Untreated porous titanium and n…