Interactions of cationic porphyrins with double-stranded oligodeoxynucleotides: a study by electrospray ionisation mass spectrometry

Electrospray ionisation mass spectrometry (ESI-MS), electrospray ionisation tandem mass spectrometry (ESI-MS/MS) and Ultraviolet-visible (UV-vis) spectroscopy were used to investigate the non-covalent interactions between small oligonucleotide duplexes with the GC motif and a group of cationic meso(N-methylpyridynium-4-yl)porphyrins (four free bases with one to four positive charges, and the zinc complex of the tetracationic free base).The results obtained point to outside binding of the porphyrins, with the binding strength increasing with the number of positive charges. Fragmentations involving losses from both chains were observed for the porphyrins with N-methylpyridinium-4-yl groups in opposite meso positions.     

Synthesis and Some Reactions of 2‐Acyl‐2‐alkyl‐1,3‐dithiolane 1,1‐Dioxides

The selective formation of optically active 2‐acyl‐2‐alkyl‐1,3‐dithiolane 1,1‐dioxides from the corresponding 2‐acyl‐2‐alkyl‐1,3‐dithiolane 1‐oxides, by reaction with OsO₄ and NMO in acetone, is reported. These compounds underwent stereoselective reactions at the carbonyl group of the acyl group with organometallic reagents. These reactions were completely regioselective, and no attack at either of the S‐atoms was observed, unlike similar reactions with the corresponding sulfoxides. The nature of the metal atom had a direct effect upon the configuration of the product alcohols.     

Preparation of nanocomposites by reversible addition‐fragmentation chain transfer polymerization from the surface of quantum dots in miniemulsion

Herein, we report the synthesis of quantum dots (QDs)/polymer nanocomposites by reversible addition‐fragmentation chain transfer (RAFT) polymerization in miniemulsions using a grafting from approach. First, the surfaces of CdS and CdSe QDs were functionalized using a chain transfer agent, a trisalkylphosphine oxide incorporating 4‐cyano‐4‐(thiobenzoylsulfanyl)pentanoic acid moieties. Using a free radical initiator (AIBN) to activate the RAFT process, a polystyrene (PS) block was grafted from the surface of the QDs. Quantum confinement effects were identified for the nanocomposite obtained, so attesting to the integrity of the QDs after the polymerization. Free PS chains were also present in the final nanocomposite, indicating that the RAFT polymerization from the surface of the QDs was accompanied by conventional free radical polymerization. After isolating the nanocomposite particles, a second poly(n‐butyl acrylate) block was tentatively grown from the initial PS block. The first results indicated a successful polymerization of the second polymer and show the potential of the current strategy to prepare block copolymers from the surface of the RAFT‐modified QDs. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5367–5377, 2009     

Synthesis and structure elucidation of three series of nitro‐2‐styrylchromones using 1D and 2D NMR spectroscopy

2‐Styrylchromones, although scarce in nature, constitute a group of oxygen heterocyclic compounds which have shown significant biological activities. New nitro‐2‐styrylchromones have been synthesised by the Baker–Venkataraman method, and the structure elucidation was accomplished using extensive 1D (1H, 13C) and 2D NMR spectroscopic studies (COSY, HSQC and HMBC experiments). Copyright © 2009 John Wiley & Sons, Ltd.     

Electrochemical study and analytical applications for new biologically active 2-nitrophenylbenzimidazole derivatives

The present study addresses the electrochemical behavior and the analytical applications of six 2-nitrophenylbenzimidazole derivatives with activity against Trypanosoma cruzi. When studied in a wide range of pH, by differential pulse polarography, tast polarography and cyclic voltammetry, these compounds exhibited two irreversible cathodic responses. With analytical purposes, the differential pulse polarography mode was selected, which exhibited adequate analytical parameters of repeatability, reproducibility and selectivity. The percentage of recovery was in all cases over 99%, and the detection and quantitation limits were at the level of 1 × 10⁻⁷ mol L⁻¹ and 1 × 10⁻⁶ mol L⁻¹, respectively. In addition, the differential pulse polarography method was successfully applied to study the hydrolytic degradation kinetic of one of the tested compounds. Activation energy, kinetic rate constants at different temperatures and half-life values of such application are reported.     

Biomechanical model for the determination of forces on upper-extremity members during standard wheelchair propulsion

New technologies and new configurations have brought great improvements to wheelchair development. These developments create problems for wheelchair users concerned with the choice of the best wheelchair for their specific needs, skills and capabilities. Handicapped people, who exclusively depend on the manual wheelchair for locomotion, face great difficulties because they have constant pain in their upper-extremity members, mainly in the shoulder, elbow and wrist. Manual propulsion can be considered a cyclical effort, thus the pains are symptoms of injuries from repetitive efforts. The problem becomes worse when the user has to overcome architectural obstacles, because it significantly increases the required propulsion force. The aim of this paper is to determine the dynamical efforts over the upper-extremity members during the manual wheelchair propulsion using Newton–Euler and Jourdain equations, and inverse dynamic techniques. The dynamical efforts consider the forces and moments over upper-extremity joints during the propulsion movement. As a result, it is possible to establish a system of equations and thus evaluate the efforts over the joints. Another result is the possibility to simulate the system using the anthropometric values of real subjects aiming at making it easier to choose the best wheelchair, considering his/her physical and anthropometric characteristics. Besides, the study of the propulsion patterns (different patterns of propulsion lead to different biomechanics) allows physical training aimed at improving the propulsion efficiency.     

Assessing microsatellite instability with semiautomated fluorescent technology: application to the analysis of primary brain tumors

The replication error phenotype, revealed by the observation of widespread microsatellite instability (MIN), has been identified as a new mechanism of cancer susceptibility, and the comparison of the allele sizes of polymorphic microsatellite repeats between normal and tumor DNA is now frequently undertaken in colorectal and other human neoplasias. The lack of precise characterization of the electrophoretic profiles of microsatellites is one of the main sources of discord between the rate of MIN reported for the same type of tumor by different investigators. The recent introduction of fluorescent-based semiautomated microsatellite analysis allows a more accurate size comparison, but one or more artificial peaks, generated during polymerase chain reaction (PCR) and/or electrophoresis, are frequently detected along with the true allele peaks. The aim of this study was to characterize the most frequent artificial extra peaks in the short tandem repeats (STRs) used by us to assess MIN in human cancers. We analyzed eight microsatellite loci in 113 primary brain tumors. HumFibra/FGA exhibited the most frequent extra peak formation. For each microsatellite there is a characteristic pattern of artifact formation which must be recognized to avoid a false-positive diagnosis of MIN.     

Fission probabilities across the π-nucleon delta resonance

Cross-sections for the π⁺-induced fission of ²⁰⁹Bi and ²³⁵U have been measured in small steps across the 3-3 resonance to search for any mechanisms that might signal a change in the reaction mechanism across a region where strong coupling of available energy into nuclear excitation can be expected. The bismuth data are found to be in good agreement with a statistical calculation not including new mechanisms. Received: 15 August 2000 / Accepted: 23 January 2001