H2O2: a Ca2+ or Mg2+‐sensing function in statin passive diffusion

In a previous paper Guillaume's group demonstrated that magnesium (Mg²⁺ concentration range 0.00–2.60 mm ) increased the passive diffusion of statins and thus played a role in their potential toxicity. In order to confirm an increase in this passive diffusion by divalent salt cations, the role of calcium chloride (CaCl₂) on the statin–immobilized artificial membrane (IAM) association was studied. It was demonstrated that calcium supplementation (Ca²⁺ concentration range 0.00–3.25 mm ) increases the statin passive diffusion. In addition, it was shown that the Ca²⁺ effect on the statin–IAM association is higher than that of Mg²⁺. These results show that Ca²⁺ enhances the passive diffusion of drugs into biological membranes and thus their potential toxicity. Also, addition of H₂O₂ to the medium showed a hyperbolic response for the statin passive diffusion and this effect was enhanced for the highest Ca²⁺ or Mg²⁺ concentrations in the medium. H₂O₂ is likely to interact with the polar head groups of the IAM through dipole–dipole interactions. The conformational changes in H₂O₂–IAM result in a higher degree of exposure of hydrophobic areas, thus explaining why the binding of pravastatin, which showed the lowest logP value, was less affected by H₂O₂. This result shows the significant contribution of H₂O₂ and thus the oxidative stress on the statin passive diffusion. Much of the sensitivity derives from the action of Ca²⁺ or Mg²⁺, in turn supported the idea that H₂O₂ may serve a Ca²⁺ or Mg²⁺ sensing function in statin passive diffusion Copyright © 2015 John Wiley & Sons, Ltd.     

Hybrids of silver nanoparticles with amphiphilic hyperbranched macromolecules exhibiting antimicrobial properties

Hybrids of silver particles of 1 to 2 nm in size with highly branched amphiphilically modified polyethyleneimines adhere effectively to polar substrates providing environmentally friendly antimicrobial coatings.     

Crystallographic and spectroscopic evidence for high affinity binding of FeEDTA(H2O)- to the periplasmic nickel transporter NikA

Because nickel is both essential and toxic to a great variety of organisms, its detection and transport is highly regulated. In Escherichia coli and other related Gram-negative bacteria, high affinity nickel transport depends on proteins expressed by the nik operon. A central actor of this process is the periplasmic NikA transport protein. A previous structural report has proposed that nickel binds to NikA as a pentahydrate species. However, both stereochemical considerations and X-ray absorption spectroscopic results are incompatible with that interpretation. Here, we report the 1.8 A resolution structure of NikA and show that it binds FeEDTA(H2O)- with very high affinity. In addition, we provide crystallographic evidence that a metal-EDTA complex was also bound to the previously reported NikA structure. Our observations strongly suggest that nickel transport in E. coli requires the binding of this metal ion to a metallophore that bears significant resemblance to EDTA. They also provide a basis for the potential use of NikA in the bioremediation of toxic transition metals and the design of artificial metalloenzymes.     

Synthesis, relaxometric and photophysical properties of a new pH-responsive MRI contrast agent: the effect of other ligating groups on dissociation of a p-nitrophenolic pendant arm

Two gadolinium(III) chelates, GdNP-DO3A (1-methlyene-(p-NitroPhenol)-1,4,7,10-tetraazacycloDOdecane-4,7,10-triAcetate) and GdNP-DO3AM (1-methlyene(p-NitroPhenol)-1,4,7,10-tetraazacycloDOdecane-4,7,10-triacetAMide), containing a single nitrophenolic pendant arm plus either three acetate or three amide pendant arms were synthesized and characterized. The properties of the gadolinium, terbium, and dysprosium complexes of these ligands were examined as a function of pH. The extent and mechanism of the changes in water relaxivity with pH of each gadolinium complex was found to differ substantially for the two complexes. The water relaxivity of Gd(NP-DO3A) increases from 4.1 mM(-1) s(-1) at pH 9 to 7.0 mM(-1) s(-1) at pH 5 as a result of acid-catalyzed dissociation of the nitrophenol from the lanthanide. The nitrophenol group in Gd(NP-DO3AM) does not dissociate from the metal center even at pH 5; therefore, the very modest increase in relaxivity in this complex must be ascribed to an increase in prototropic exchange rate of the bound water and/or phenolic protons.     

新颖结构的钛锆钒异核双金属配合物[Cp_2V(μ-η~2:η~4-PhC_4Ph)MCp_2](M=Ti，Zr)

室温下，[Cp_2Ti(C≡CPh)_2]和[Cp_2Zr(C≡CPh)_2]分别与二茂钒作用，首次 合成了[Cp_2V(μ-η~2:η~4-PhC_4Ph)MCp_2] 1 (M = Ti), 2 (M = Zr)。用元素 分析、质谱、磁矩、红外和拉曼光谱对配合物进行了表征，两个配合物具有相似的 磁化率，配合物2的晶体结构分析表明PhC_4Ph通过内部两个碳原子键合到Cp_2V上 ，内部两个碳原子和外部两个碳原子均与Cp_2Zr键合，丁二烯骨架内部的两个碳原 子都具有四配位的平面结构。用核磁跟踪技术初步探讨了合成反应机理。     

Complexation diastereoselective d''alcools benzyliques par le chrome hexacarbonyle. Difference de reactivite des diastereoisomeres en milieu acide.

Reaction of ortho alkyl or alkoxy phenyl carbinol with Cr(CO)₆ affords arene chromium tricarbonyl complexes with 38 to 86% of diastereoisomeric excess. The behavior of the two diastereoisomers shows a striking difference. Equimolar mixture of (RR,SS) and (RS,SR) diastereoisomers treated with concentrated sulfuric acid and methanol gives (RS,SR) ether while (RR,SS) alcool remains unchanged.     

Use of ionic liquids in sol-gel; ionogels and applications

The current strong interest in ionic liquids is motivated by their unique combination of properties such as negligible vapour pressure, thermal stability, non-flammability, high ionic conductivity and wide electrochemical stability window. The first part of this short review deals with all the specific aspects of sol-gel in the presence of ionic liquid, which can act as drying control chemical additive, catalyst, porogenous agent and solvent or co-solvent. The second part is devoted to the properties of the gels in which the ionic liquid is kept confined (ionogels) and their applications as electrolyte membranes, optical devices, catalysts and sensors.