Synthesis of telechelic oligomers by atom transfer radical polymerization: A study of acrylate monomers

Different acrylate oligomers were synthesized by atom transfer radical polymerization in the presence of a transfer agent and CuBr/1,1,4,7,10,10‐hexamethyltriethylenetetramine. The functionality in bromine was determined by ¹H NMR. These oligomers were coupled in the presence of Cu⁽⁰⁾ and the ligand 2,2′‐bipyridine. The coupling yield was determined by size exclusion chromatography and NMR analysis and depended on the nature of the monomer and not on the molecular weight. In other words, the preliminary functionalization of the brominated chain end with styrene increased the coupling yield. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2377‐2394, 2005     

Quantitative roughness of sputtered Fe-Cr superlattices

The European Physical Journal B - We obtained quantitative values of all significant parameters describing the roughness of Fe-Cr superlattices, both in the lateral and growth directions, by...     

Calix[n]arenes as components for the construction of micellar systems: synthesis and self-assembly properties of 5,11,17-Tris[(dimethylamino)methyl]-25-monoalkoxy-26,27,28-trihydroxycalix[4]arene derivatives

A series of mono-O-alkylated calix [4] arenes derivatives, with alkyl chain lengths of between 1 and 12 carbon atoms are reported. Monoalkylation is best achieved using potassium carbonate as the weak base and the respective alkyl iodide for chain lengths of one to three carbon atoms and using caesium fluoride as the base and the respective alkyl iodide for longer chain lengths. The mono-alkylated derivatives were converted into the tri-para-dimethylaminomethylene derivatives by the para-quinonemethide reaction in good yields. Surface tension measurements showed that at pH 2, 4, 6 and 8 all the tri-dimethylaminomethylene derivatives showed surfactant behaviour, and at pH 2 all show a Critical Micellar Concentration values. No correlation between Critical Micellar Concentration values and chain length is observed. Dynamic Light Scattering measurements showed that the CMC behaviour may be correlated with the observed aggregate sizes. The solid state structure of mono-O-ethoxy-calix[4]arene is described, in this structure a 1-D inclusion polymer is observed.     

Synthesis and in vivo evaluation of 4-deoxy-4,4-difluoro-KRN7000

The synthesis of 4-deoxy-4,4-difluoro-KRN7000 starting from phytosphingosine is described. Key steps include a regioselective benzylation of azidophytosphingosine and a deoxofluor-mediated fluorination of the corresponding 4-ketone. This fluorination failed completely when the adjacent 3-OH was protected as benzyl ether but proceeded well when a benzoyl group was used. The biological evaluation reveals a bias toward Th1 cytokine induction upon Natural Killer T cell activation.     

Imidazole-substituted oxoverdazyl radical as a mediator of intramolecular and intermolecular exchange interaction

The 3-(2'-imidazolyl)-1,5-dimethyl-6-oxoverdazyl radical (imvd(*)) and the corresponding tetrazane H3imvd were prepared and structurally characterized, the former as two different hydrates. Reaction of imvd(*) with [M(hfac)2] led to the formation of monometallic complexes [M(hfac)2(imvd(*))] (M = Ni and Mn). They were characterized by single-crystal X-ray diffraction. In the solid state, all four radical-containing compounds exhibit imidazole-oxoverdazyl pi stacking. Following the structural analysis, imvd(*) behaves as an antiferromagnetic (AF) coupled chain with J = -100 cm(-1) (H = -J summation operator SiS(i+1)). The magnetic behavior of [M(hfac)2(imvd(*))] complexes is interpreted with a four-coupled spin model with a metal ion radical intramolecular interaction (JMn = -62.5 cm(-1) and JNi = 193 cm(-1); H = -JSMSimvd) and an AF intermolecular interaction (JMn' = -12.6 cm(-1) and JNi' = -4.3 cm(-1)) related to imidazole-oxoverdazyl pi stacking.     

Tetracyanoresorcin[4]arene selectively recognises trimethyllysine and inhibits its enzyme-catalysed demethylation

Abstract

Nε-methylation of lysine within proteins is a critical biological process that, among other roles, is involved in the control of gene expression. Compounds that recognise Nε-methylated lysine may therefore be useful probes for the study of the associated biological mechanisms and have therapeutic potential. Here, we show that tetracyanoresorcin[4]arene (1) selectively recognises Nε-trimethyllysine and binds to Nε-trimethyllysine within the context of a short peptide. Its binding properties compare favourably to a previously characterised Nε-trimethyllysine binder, p-sulfonatocalix[4]arene (2). We also show that both 1 and 2 inhibit the demethylation of Nε-trimethyllysine within a histone-derived peptide by the histone demethylase KDM4A.     

Concerted proton-electron transfer reactions in water. are the driving force and rate constant depending on pH when water acts as proton donor or acceptor?

The competition between stepwise and concerted (CPET) pathways in proton-coupled electron-transfer reactions in water is discussed on thermodynamic and kinetic bases. In the case where water is the proton acceptor, the CPET pathway may compete favorably with the stepwise pathway. The main parameter of the competition is pK of the oxidized form of the substrate being smaller or larger than 0. The driving force of the forward reaction is however independent of pH, despite the equilibrium redox potential of the proton-electron system being a function of pH. At high pH values, CPET reactions involving OH- as proton acceptor may likewise compete favorably with stepwise pathways. The overall reaction rate constant is an increasing function of pH, not because the driving force depends on pH but because OH- is a reactant. In buffered media, association of the substrate with the basic components of the buffer offers an alternative CPET route; the driving force comes closer to that offered by the pH-dependent equilibrium redox potential.     

A stereoselective entry into functionalized 1,2-diamines by zinc-mediated homologation of alpha-aminoacids

A general, stereoselective synthesis of 4,5-disubstituted imidazolidines-2-ones from alpha-aminoacids has been developed: the key steps are a Blaise reaction of bromoacetate on alpha-aminonitriles and further reduction. Although reduction with sodium cyanoborohydride afforded a mixture of cis and trans isomers 6a-e with moderate to good stereoselectivity, reduction with sodium in liquid ammonia gave the trans isomers 8a-e with complete stereoselectivity. Acidic hydrolysis of the urea gave 4-amino-pyrrolidinones, which can be precursors to beta,gamma-diaminoacids or 3-aminopyrrolidines.     

A multi-channel bioluminescent bacterial biosensor for the on-line detection of metals and toxicity. Part II: technical development and proof of concept of the biosensor

This research study deals with the on-line detection of heavy metals and toxicity within the context of environmental pollution monitoring. It describes the construction and the proof of concept of a multi-channel bioluminescent bacterial biosensor in immobilized phase: Lumisens3. This new versatile device, designed for the non-stop analysis of water pollution, enables the insertion of any bioluminescent strains (inducible or constitutive), immobilized in a multi-well removable card. The technical design of Lumisens3 has benefited from both a classical and a robust approach and includes four main parts: (1) a dedicated removable card contains 64 wells, 3 mm in depth, arranged in eight grooves within which bacteria are immobilized, (2) this card is incubated on a Pelletier block with a CCD cooled camera on top for bioluminescence monitoring, (3) a fluidic network feeds the card with the sample to be analyzed and finally (4) a dedicated computer interface, BIOLUX 1.0, controls all the elements of the biosensor, allowing it to operate autonomously. The proof of concept of this biosensor was performed using a set of four bioluminescent bacteria (Escherichia coli DH1 pBzntlux, pBarslux, pBcoplux, and E. coli XL1 pBfiluxCDABE) in the on-line detection of CdCl₂ 0.5 μM and As₂O₃ 5 μM from an influent. When considering metals individually, the “fingerprints” from the biosensor were as expected. However, when metals were mixed together, cross reaction and synergistic effects were detected. This biosensor allowed us to demonstrate the simultaneous on-line cross detection of one or several heavy metals as well as the measurement of the overall toxicity of the sample.