Glycopolymers obtained by chemical modification of well‐defined block copolymers

Well‐defined di and triblock copolymers based on 2‐hydroxyethyl methacrylate, HEMA, and n‐butyl acrylate, BA, have been synthesized by atom transfer radical polymerization, ATRP. Two copolymers have been selected to prepare glycopolymers containing D ‐(+)‐glucosamine or N‐(4‐aminobutyl)‐D ‐gluconamide, NABG, by chemical modification of HEMA units. The chemical modification occurs by activation of the hydroxyl groups of the HEMA units with highly reactive p‐nitrophenyl carbonate groups. The block copolymers structure and self‐assembly have been comprehensively studied in solid state and in solution by differential scanning calorimetry, X‐ray diffraction, atomic force microscopy and dynamic light scattering. The resulting glycopolymers obtained upon chemical modification turned out to be water soluble. Therefore, their carbohydrate‐lectin interactions of have been analyzed by turbidimetry measurements. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Experimental study of a SmA*-SmC*A phase transition

We have performed a detailed experimental study of the electroclinic behaviour in the SmA* phase above a SmA*-SmC*_A phase transition. The tilt angle and polarization were measured as a function of the applied a.c. electric field, and the dielectric constant was obtained under different values of the bias field (0≤E _d.c.≤ 3 V μm^-1). In the region of linear regime, the behaviour observed for this SmA*-SmC*_A phase transition is very similar to the one previously described for SmA*-SmC* phase transitions. The experimental results obtained under high bias field are in good agreement with the predictions of the simple theoretical model considered.     

Controlled block glycopolymers able to bind specific proteins

The syntheses of a variety of amphiphilic block glycopolymers based on 2‐{[(D ‐glucosamin‐2‐N‐yl)carbonyl]oxy}ethyl acrylate and n‐butyl acrylate or methyl methacrylate by single‐electron transfer‐living radical polymerization (SET‐LRP) are described. In a first step, the homopolymerization of unprotected acrylic glycomonomer to obtain well‐controlled glycopolymers is studied. Posterior and based on these studies, di‐ and triblock glycopolymers were synthesized via SET‐LRP of the glycomonomer from different hydrophobic blocks, varying the hydrophilic block lengths. All the copolymers are characterized by nuclear magnetic resonance spectroscopy and GPC. Moreover, their water solution behavior by dynamic light scattering and their capacity of interaction with Concanavalin A lectin by turbidimetry are analyzed. The effect on the block glycopolymers behavior of hydrophobic block nature and the length of glycopolymer segments is evaluated. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Spectral Properties of Interval Exchange Maps

 In [7], Nogueira and Rudolph proved that for irreducible permutations not of rotation class almost every (a.e.) interval exchange transformation (i.e.t.) is topological weak mixing. It is conjectured that the claim holds if topological weak mixing is replaced by weak mixing. Here we study the behaviour of eigenfunctions of i.e.t. Our analysis gives alternative proofs of results due to Katok and Stepin [4] and Veech [10]: for certain permutations a.e. i.e.t. is weak mixing and for irreducible permutations a.e. i.e.t. is totally ergodic.     

New Tris(hydroxypyridinones) as Iron and Aluminium Sequestering Agents: Synthesis,Complexation and In Vivo Studies

Two new tripodal tris(3‐hydroxy‐4‐pyridinone) hexadentate chelators—NTA(BuHP)₃ and NTP(PrHP)₃ (NTA=nitrilotriacetic acid, NTP=nitrilotripropionic acid, HP=hydroxypyridone)—have been developed and studied in solution for their iron and aluminium binding affinity, and also assayed in vivo for their capacity to remove metal from an animal model that is overloaded. These chelators are positional isomers, possessing identical general structures based on aminotricarboxylic acid skeletons attached to three bidentate 3‐hydroxy‐4‐pyridinones (3,4‐HPs), but differing in the position of the amide linkage along the chelating “arm”. In spite of expected differences in the tripodal ligands, such as acidity and hydrogen‐bonding networks, they share important properties, namely, a mild hydrophilic character (log P ca. ?1.2 to ?1.4) and a strong chelating affinity for Fe and Al (pFe=27.9 and pAl=22.0 for NTA(BuHP)₃; pFe=29.4 and pAl=22.4 for NTP(PrHP)₃). They also evidenced identical effects on the biodistribution and on the excretion of a radiotracer (⁶⁷Ga) previously administered to mice, as models of iron overload animals. Comparison of the new compounds with reported analogues shows good improvement in terms of solution and in vivo sequestering properties, thus giving support to expectations about their potential clinical application as metal removal agents.     

Phenolic Derivatives from Fruits of Dipteryx lacunifera Ducke and Evaluation of Their Antiradical Activities

The fruits of Dipteryx lacunifera, known as ‘fava de morcego’ and ‘garampara’, comprise pleasant tasting kernels that contain high amounts of fatty acids (mainly oleic acid) and are commonly consumed by inhabitants of the northeast of Brazil. In the present study, the crude EtOH extract of the fruit kernels was separated into hexane‐, Et₂O‐, AcOEt‐, and H₂O‐soluble fractions. The Et₂O fraction was found to exhibit the highest 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical‐scavenging activity in vitro, and was subjected to further fractionation. Column chromatography over silica gel and Sephadex LH‐20, followed by preparative HPLC‐C₁₈, afforded (?)‐eriodictyol ( 1 ), (?)‐butin ( 2 ), luteolin ( 3 ), 3′,4′,7‐trihydroxyflavone ( 4 ), butein ( 5 ), and sulfuretin ( 6 ). The antiradical activities of compounds 1, 2, 4 , and 6 , together with the positive controls rutin, butylated hydroxy toluene (BHT), and tert‐butylhydroquinone (TBHQ), were evaluated with the DPPH assay and were found to decrease in the order rutin> 4 > 1 > 6 > 2 >TBHQ>BHT.     

Organic metabolites in exhaled human breath—A multivariate approach for identification of biomarkers in lung disorders

The gas chromatographic profiles of exhaled air from lung cancer patients have been investigated. The breath from healthy volunteers, smokers and non-smokers, and lung cancer patients without treatment and under radio and/or chemotherapy, was collected using Tedlar bags. Different profiles for healthy people and cancer patients could be recognized by multivariate analysis and significant diagnostic compounds could be established. Target compounds showed to be linear and branched hydrocarbons between C₁₄ and C₂₄. Solid phase microextraction (SPME) coupled to gas chromatography mass spectrometry GC–(TOF)-MS was used. The method showed good precision (RSD below 26%) and limit of detection ranged from 0.04 to 8.0 ppb. These findings show a high potential for establishment of laboratorial screening methods. Validation studies in a larger number of patients are being done.     

Toward an alternative hardness kernel matrix structure in the Electronegativity Equalization Method (EEM)

This study presents an alternative of the Electronegativity Equalization Method (EEM), where the usual Coulomb kernel has been transformed into a smooth function. The new framework, as the classical EEM, permits fast calculations of atomic charges in a given molecule for a small computational cost. The original EEM procedure needs to previously calibrate the different implied atomic hardness and electronegativity, using a chosen set of molecules. In the new EEM algorithm half the number of parameters needs to be calibrated, since a relationship between electronegativities and hardnesses has been found.