Search results for "HeLa"
showing 10 items of 738 documents
Synthesis of C-17-functionalized spongiane diterpenes: diastereoselective synthesis of (-)-spongian-16-oxo-17-al, (-)-acetyldendrillol-1, and (-)-apl…
2003
The diastereoselective synthesis of spongiane diterpenes (-)-spongian-16-oxo-17-al 2, (-)-acetyldendrillol-1 15, and (-)-aplyroseol-14 16 has been completed efficiently via the common intermediate 14. Compound 14 was prepared in five synthetic steps from (+)-podocarp-8(14)-en-13-one 13, easily available from commercial (-)-abietic acid. The key steps in the syntheses were a regioselective reduction of a 1,4-dialdehyde unit, a one-pot acetalization-acetylation, and a translactonization. The synthesis of 15 and 16 has led us to a revision of the configuration at C-17 for natural (-)-acetyldendrillol-1 and a structural reassignment for aplyroseol-14. Thus, aplyroseol-14 16 presents an unpreced…
Bioinspired manganese(II) complexes with a clickable ligand for immobilisation on a solid support.
2014
International audience; Clickable ligands like N,N′-bis((pyridin-2-yl)methyl)prop-2-yn-1-amine (L1) and N-((1-methyl-1H-imidazol-2-yl)methyl)-N-(pyridin-2-ylmethyl)prop-2-yn-1-amine (L2) have been used to synthesise a series of manganese(II) complexes for grafting onto appropriate solid supports. These ligands mimic the 2-His-1-carboxylate facial chelation present in the active site of the manganese-dependent dioxygenase (MndD), while the alkyne side function allows grafting of the ligand onto an azido-functionalised support using “click chemistry” methodologies. Such synthetic analogues of the MndD crystallise in the solid state as double halide or pseudohalide-bridged dinuclear manganese(…
Asymmetric synthesis of chloroisothreonine derivatives via syn-stereoselective Mannich-type additions across N-sulfinyl-α- chloroimines
2014
Mannich-type reactions of O-Boc glycolic esters across chiral N-sulfinyl-α-chloroaldimines resulted in the efficient and syn-stereoselective synthesis of new γ-chloro-α-hydroxy-β-amino esters (dr > 99:1). The α-coordinating ability of the chlorine atom was of great importance for the diastereoselectivity of the Mannich-type reaction and overruled the chelation of the sulfinyl oxygen with the lithium ion of the incoming E-enolate in the transition state model. These novel chloroisothreonine derivatives proved to be excellent building blocks in asymmetric synthesis of novel syn-β,γ-aziridino-α-hydroxy esters and biologically relevant trans-oxazolidinone carboxylic esters.
Coordination Chemistry of 6-Thioguanine Derivatives with Cobalt: Toward Formation of Electrical Conductive One-Dimensional Coordination Polymers
2013
In this work we have synthetized and characterized by X-ray diffraction five cobalt complexes with 6-thioguanine (6-ThioGH), 6-thioguanosine (6-ThioGuoH), or 2'-deoxy-6-thioguanosine (2'-d-6-ThioGuoH) ligands. In all cases, these ligands coordinate to cobalt via N7 and S6 forming a chelate ring. However, independently of reagents ratio, 6-ThioGH provided monodimensional cobalt(II) coordination polymers, in which the 6-ThioG(-) acts as bridging ligand. However, for 2'-d-6-ThioGuoH and 6-ThioGuoH, the structure directing effect of the sugar residue gives rise to mononuclear cobalt complexes which form extensive H-bond interactions to generate 3D supramolecular networks. Furthermore, with 2'-d…
Chelate Cooperativity and Spacer Length Effects on the Assembly Thermodynamics and Kinetics of Divalent Pseudorotaxanes
2011
Homo- and heterodivalent crown-ammonium pseudorotaxanes with different spacers connecting the two axle ammonium binding sites have been synthesized and characterized by NMR spectroscopy and ESI mass spectrometry. The homodivalent pseudorotaxanes are investigated with respect to the thermodynamics of divalent binding and to chelate cooperativity. The shortest spacer exhibits a chelate cooperativity much stronger than that of the longer spacers. On the basis of crystal structure, this can be explained by a noninnocent spacer, which contributes to the binding strength in addition to the two binding sites. Already very subtle changes in the spacer length, i.e., the introduction of an additional…
Identification and relevance of the CD95-binding domain in the N-terminal region of ezrin.
2003
The CD95 (Fas/APO-1) linkage to the actin cytoskeleton through ezrin is an essential requirement for susceptibility to the CD95-mediated apoptosis in CD4+ T cells. We have previously shown that moesin was not involved in the binding to CD95. Here we further support the specificity of the ezrin/CD95 binding, showing that radixin did not bind CD95. The ezrin region specifically and directly involved in the binding to CD95 was located in the middle lobe of the ezrin FERM domain, between amino acids 149 and 168. In this region, ezrin, radixin, and moesin show 60-65% identity, as compared with the 86% identity in the whole FERM domain. Transfection of two different human cell lines with a green …
Monitoring the formation of biosilica catalysed by histidine-tagged silicatein.
2004
Surface bound silicatein retains its biocatalytic activity, which was demonstrated by monitoring the immobilisation of silicatein using a histidine-tag chelating anchor and the subsequent biosilicification of SiO(2) on surfaces by surface plasmon resonance spectroscopy, atomic force microscopy and scanning electron microscopy.
Synthesis, structure and reactivity of trans-UO22+ complexes of OH-containing ligands †
2000
trans-Dioxouranium dinuclear complexes of a few OH-containing ligands possessing N-, O-binding sites were synthesized and characterised. Seven of these were also structurally characterised by single crystal X-ray diffraction. All these complexes exhibit symmetric U2O2 core structures in addition to having a seven-co-ordinated environment about each uranium centre. Even when the ligand possessed more than one CH2OH group, only one such group was found to be involved both in chelation as well as in bridging. These complexes exhibited facile transmetallation reactions with vanadium and molybdenum precursors. Though their core structures are alike, the complexes differ in their lattice arrangem…
Stereoselective Synthesis and Cytoselective Toxicity of Monoterpene-Fused 2-Imino-1,3-thiazines
2014
Starting from pinane-, apopinane- and carane-based 1,3-amino alcohols obtained from monoterpene-based β-amino acids, a library of monoterpene-fused 2-imino-1,3-thiazines as main products and 2-thioxo-1,3-oxazines as side-products were prepared via two- or three-step syntheses. When thiourea adducts prepared from 1,3-amino alcohols and aryl isothiocyanates were reacted with CDI under mild conditions, O-imidazolylcarbonyl intermediates were isolated which could be transformed to the desired 1,3-thiazines under microwave conditions. 1,3-Thiazines and 2-thioxo-1,3-oxazine side-products could also be prepared in one-step reactions through the application of CDI and microwave irradiation. The rin…
Toxicological properties of two fluorescent carbon quantum dots with onion ring morphology and their usefulness as bioimaging agents
2016
In the present work, two carbon quantum dots with onion ring morphology, C-NOR and C-NOR(Eu) with an average size of 40 nm differing in the absence or presence of Eu3+ as Lewis acids during their preparation were synthesized and fully characterized by several techniques. These nanoparticles can be internalized into human HeLa and Hep3B carcinoma cells where they exhibit interesting photoluminescent properties, in the same manner as in solution, confirming their utility as bioimaging agents. To address this possibility, a complete in vitro toxicological study has been performed here. Viability, proliferation, apoptosis and oxidative stress assessments upon limited or continuous exposure were…