14,443 research outputs found
Copper(II)- and gold(III)-mediated cyclization of a thiourea to a substituted 2-aminobenzothiazole
Benzothiazole derivatives are a class of privileged molecules due to their biological activity and pharmaceutical applications. One route to these molecules is via intramolecular cyclization of thioureas to form substituted 2-aminobenzothiazoles, but this often requires harsh conditions or employs expensive metal catalysts. Herein, the copper(II)- and gold(III)-mediated cyclizations of thioureas to substituted 2-aminobenzothiazoles are reported. The single-crystal X-ray structures of the thiourea N-(3-methoxyphenyl)-N\u27- (pyridin-2-yl)thiourea, C13H13N3OS, and the intermediate metal complexes aquabis[5-methoxy-N-(pyridin-2-yl-κN)-1,3-benzothiazol-2-amine-κN3]copper(II) dinitrate, [Cu(C13H11N3OS)2(H2O)](NO3)2, and bis{2-[(5-methoxy-1,3-benzothiazol- 2-yl)amino]pyridin-1-ium} dichloridogold(I) chloride monohydrate, (C13H12N3OS)2[AuCl2]Cl⋅H2O, are reported. The copper complex exhibits a distorted trigonal–bipyramidal geometry, with direct metal-to-benzothiazoleligand coordination, while the gold complex is a salt containing the protonated uncoordinated benzothiazole, and offers evidence that metal reduction (in this case, AuIII to AuI) is required for the cyclization to proceed. As such, this study provides further mechanistic insight into the role of the metal cations in these transformations
Energies of Quantum QED Flux Tubes
In this talk I present recent studies on vacuum polarization energies and
energy densities induced by QED flux tubes. I focus on comparing three and four
dimensional scenarios and the discussion of various approximation schemes in
view of the exact treatment.Comment: 9 pages latex, Talk presented at the QFEXT 05 workshop in Barcelona,
Sept. 2005. To appear in the proceeding
Quantum stabilization of Z-strings, a status report on D=3+1 dimensions
We investigate an extension to the phase shift formalism for calculating
one-loop determinants. This extension is motivated by requirements of the
computation of Z-string quantum energies in D=3+1 dimensions. A subtlety that
seems to imply that the vacuum polarization diagram in this formalism is
(erroneously) finite is thoroughly investigated.Comment: Based on talk by O.S. at QFEXT07, Leipzig Sept. 2007. 8 page
Syndecan-4 knockout leads to reduced extracellular transglutaminase-2 and protects against tubulointerstitial fibrosis
Transglutaminase type 2 (TG2) is an extracellular matrix crosslinking enzyme with a pivotal role in kidney fibrosis. The interaction of TG2 with the heparan sulfate proteoglycan syndecan-4 (Sdc4) regulates the cell surface trafficking, localization, and activity of TG2 in vitro but remains unstudied in vivo. We tested the hypothesis that Sdc4 is required for cell surface targeting of TG2 and the development of kidney fibrosis in CKD. Wild-type and Sdc4-null mice were subjected to unilateral ureteric obstruction and aristolochic acid nephropathy (AAN) as experimental models of kidney fibrosis. Analysis of renal scarring by Masson trichrome staining, kidney hydroxyproline levels, and collagen immunofluorescence demonstrated progressive fibrosis associated with increases in extracellular TG2 and TG activity in the tubulointerstitium in both models. Knockout of Sdc-4 reduced these effects and prevented AAN-induced increases in total and active TGF-b1. In wild-type mice subjected to AAN, extracellular TG2 colocalized with Sdc4 in the tubular interstitium and basement membrane, where TG2 also colocalized with heparan sulfate chains. Heparitinase I, which selectively cleaves heparan sulfate, completely abolished extracellular TG2 in normal and diseased kidney sections. In conclusion, the lack of Sdc4 heparan sulfate chains in the kidneys of Sdc4-null mice abrogates injury-induced externalization of TG2, thereby preventing profibrotic crosslinking of extracellular matrix and recruitment of large latent TGF-b1. This finding suggests that targeting the TG2- Sdc4 interaction may provide a specific interventional strategy for the treatment of CKD
Cd-vacancy and Cd-interstitial complexes in Si and Ge
The electrical field gradient (EFG), measured e.g. in perturbed angular
correlation (PAC) experiments, gives particularly useful information about the
interaction of probe atoms like 111In / 111Cd with other defects. The
interpretation of the EFG is, however, a difficult task. This paper aims at
understanding the interaction of Cd impurities with vacancies and interstitials
in Si and Ge, which represents a controversial issue. We apply two
complementary ab initio methods in the framework of density functional theory
(DFT), (i) the all electron Korringa-Kohn-Rostoker (KKR) Greenfunction method
and (ii) the Pseudopotential-Plane-Wave (PPW) method, to search for the correct
local geometry. Surprisingly we find that both in Si and Ge the substitutional
Cd-vacancy complex is unstable and relaxes to a split-vacancy complex with the
Cd on the bond-center site. This complex has a very small EFG, allowing a
unique assignment of the small measured EFGs of 54MHz in Ge and 28MHz in Si.
Also, for the Cd-selfinterstitial complex we obtain a highly symmetrical split
configuration with large EFGs, being in reasonable agreement with experiments
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