Exploring Liquid Sequential Injection Chromatography To Teach Fundamentals of Separation Methods: A Very Fast Analytical Chemistry Experiment

Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)

Probing the tunable surface chemistry of graphene oxide

The determination of oxygen content, hydrophobicity and reduction efficiency of graphene oxide (GO) are difficult tasks because of its heterogeneous structure. Herein, we describe a novel approach for the detailed understanding of the surface chemistry of GO by studying the interactions between [Ru(bpy)3](2+) and GO.

INVESTIGATING THE PRESENCE OF THE HISTORY OF SCIENCE IN UNIVERSITY GENERAL CHEMISTRY TEXTBOOKS

INVESTIGATING THE PRESENCE OF THE HISTORY OF SCIENCE IN UNIVERSITY GENERAL CHEMISTRY TEXTBOOKS. This paper aims at analyzing the history of science content of three general chemistry textbooks used in Brazilian universities: the translations of Kotz and Treichel's Chemistry & Chemical Reactivity, Atkins and Jones's Chemical Principles, and Garritz and Chamizo's Quimica. Results revealed different trends for the inclusion of history of science in chemistry teaching. Katz & Treichel and Atkins & Jones used history mainly as curiosity and ornament. Garritz & Chamizo adopted the historical approach as one of the organizing axis of their textbook. Nevertheless, the historical content of the three textbooks may be criticized from current historiographical standpoint.

Chemical and physical factors influencing lead and copper contamination in drinking water: approach for a case study in analytical chemistry

CHEMICAL AND PHYSICAL FACTORS INFLUENCING LEAD AND COPPER CONTAMINATION IN DRINKING WATER: APPROACH FOR A CASE STUDY IN ANALYTICAL CHEMISTRY. Lead and copper concentrations in drinking water increase considerably on going from municipality reservoirs to the households sampled in Ribeirao Preto (SP-Brazil). Flushing of only 3 liters of water reduced metal concentrations by more than 50%. Relatively small changes in water pH rapidly affected corrosion processes in lead pipes, while water hardness appeared to have a long-term effect. This approach aims to encourage University teachers to use its content as a case study in disciplines of Instrumental Analytical Chemistry and consequently increase knowledge about drinking water contamination in locations where no public monitoring of trace metals is in place.

SCIENTIFIC LANGUAGE RHETORIC: FROM THE THEORETICAL BASIS TO THE PRODUCTION OF DIDACTIC MATERIAL FOR UNDERGRADUATE CHEMISTRY TEACHING

This work is part of a study that focused on analyzing the contributions of didactic activities related to scientific language rhetoric characteristics aimed at developing students' abilities to identify such characteristics in chemistry scientific texts and critical reading of those texts. In this study, we present the theoretical basis adopted to determine the scientific discourse characteristics and for the production of the didactic material used in those activities. Latour, Coracini and Campanario studies on persuasive rhetorical strategies present in scientific articles aided the production of such material.

Cyclic Voltammetry and Computational Chemistry Studies on the Evaluation of the Redox Behavior of Parabens and other Analogues

Parabens are antimicrobial preservatives widely used in pharmaceutical, cosmetic and food industries. The alkyl chain connected to the ester group defines some important physicochemical characteristics of these compounds, including the partition coefficient and redox properties. The voltammetric and computational analyses were carried out in order to evaluate the redox behavior of these compounds and other phenolic analogues. A strong correlation between chemical substituents inductive effects of parabens with redox potentials was observed. Using cyclic voltammetry and glassy carbon working electrode, only one irreversible anodic peak was observed around 0.8 V for methylparaben (MP), ethylparaben (EP), propylparaben (PP), butylparaben (BP), benzylparaben (BzP) and p-substituted phenolic analogues. The electrodonating inductive effect of alkyl groups was demonstrated by the anodic oxidation potential shift to lower values as the carbon number increases and, therefore the parabens (and other phenolic analogues) oxidation processes to the quinonoidic forms showed great dependence on the substituent pattern.

One-pot synthesis of aminated multi-walled carbon nanotube using thiol-ene click chemistry for improvement of epoxy nanocomposites properties

A non-oxidative method based on thiol-ene click chemistry for functionalization of multi-walled carbon nanotube (CNT) was performed in order to improve the interfacial interactions between epoxy matrix and CNT. In this way, the CNT was aminated using 2-aminoethanethiol hydrochloride radicals thermally produced by a peroxide radical initiator. The aminated CNT (CNT-NH2) was characterized by FTIR, TGA, and solubility evaluations, confirming that thiol radicals are successfully grafted onto the CNT surface with a proper yield. Various percentages of pure CNT (p-CNT) and CNT-NH2 were then incorporated into epoxy matrix to evaluate the effect of the functionalization of CNT on thermal, mechanical, and morphological properties. The nanocomposites were characterized by DMA, tensile testing, and TGA. Results showed that glass transition temperature, tensile properties and thermal stability of epoxy nanocomposites containing CNT-NH2 improves significantly compared to those containing unmodified CNT. These results prove the role of amino-functionalization in improving the interfacial adhesion between epoxy and CNT, which was further confirmed by morphological observations of fracture surfaces of the nanocomposites.

Formation of single-walled carbon nanotube via the interaction of graphene nanoribbons : ab initio density functional calculations

The interaction of bare graphene nanoribbons (GNRs) was investigated by ab initio density functional theory calculations with both the local density approximation (LDA) and the generalized gradient approximation (GGA). Remarkably, two bare 8-GNRs with zigzag-shaped edges are predicted to form an (8, 8) armchair single-wall carbon nanotube (SWCNT) without any obvious activation barrier. The formation of a (10, 0) zigzag SWCNT from two bare 10-GNRs with armchair-shaped edges has activation barriers of 0.23 and 0.61 eV for using the LDA and the revised PBE exchange correlation functional, respectively, Our results suggest a possible route to control the growth of specific types SWCNT via the interaction of GNRs.

Hydrogen spillover mechanism on a pd-doped mg surface as revealed by ab initio density functional calculation

The hydrogenation kinetics of Mg is slow, impeding its application for mobile hydrogen storage. We demonstrate by ab initio density functional theory (DFT) calculations that the reaction path can be greatly modified by adding transition metal catalysts. Contrasting with Ti doping, a Pd dopant will result in a very small activation barrier for both dissociation of molecular hydrogen and diffusion of atomic H on the Mg surface. This new computational finding supports for the first time by ab initio simulationthe proposed hydrogen spillover mechanism for rationalizing experimentally observed fast hydrogenation kinetics for Pd-capped Mg materials.

VISUALIZATION OF THE CHROMOSOME SCAFFOLD IN A PRIMITIVE EUKARYOTE DINOFLAGELLATE CRYPTHECOAINIUM-COHNII

The chromosome scaffolds in higher eukaryotic nuclei have been described elsewhere. But it is unknown when they evolved. The dinoflagellates are the primitive organisms that may be the intermediate between prokaryotes and eukaryotes. Combining chromosome scaffold preparation methods with embedment-free section microscopy, we demonstrate that the dinoflagellate Crypthecodinium cohnii chromosome retains a protein scaffold after the depletion of DNA and soluble proteins. This scaffold preserves the morphology characteristic of the chromosome. Two-dimensional electrophoreses show that the chromosome scaffolds are mainly composed of acidic proteins. Our results suggest that a framework similar to the chromosome scaffold in the mammalian cell appeared in the primitive eukaryote. We propose that the chromosome scaffold possibly originated from the early stages of eukaryote evolution.

Genetic diversity and conservation of endangered animal species

The loss of biodiversity resulting from extinctions is receiving increasing attention. Over several thousands of animal species have been evaluated and recognized as endangered species. Inbreeding depression has been demonstrated in many wild animal speci

Structural analysis of human CCR2b and primate CCR2b by molecular modeling and molecular dynamics simulation

CCR2b, a chemokine receptor for MCP-1, -2, -3, -4, plays an important role in a variety of diseases involving infection, inflammation, and/or injury, as well as being a coreceptor for HIV-1 infection. Two models of human CCR2b (hCCR2b) were generated by h

Molecular dynamics simulation on the complex of the tobramycin and 16S rRNA a site

A 3. 6 ns molecular dynamics simulation was carried out on the complex system of tobramycin and 16S rRNA in order to understand the speciality recognition mechanism between tobramycin and 16S rRNA at the molecular level. The results demonstrate that two l

Anti-HIV-1 activity of trichobitacin, a novel ribosome-inactivating protein

AIM: To determine whether trichobitacin, a novel ribosome-inactivating protein purified from the root tubers of Trichosanthes kirilowii, possesses the anti-HIV activity. METHODS: The inhibition of syncytial cell formation induced by human immunodeficiency virus type 1 (HIV-1),was determined under microscope, reduction of HIV-1 p24 antigen expression level was measured by ELISA, and decrease in numbers of HIV-1 antigen positive cells in acutely and-chronically infected cultures were detected by indirect immunofluorescence assay. RESULTS: Trichobitacin Was-found to greatly suppress syncytial cell formation induced by HIV-1 and to markedly reduce both expression of HIV-1 p24 antigen and the number of HIV antigen positive cells in acutely but not chronically HIV-1 infected culture. The median inhibitory concentration (IC50) in inhibition of syncytial cell formation and HIV antigen positive cells were 5 mu g.L-1 (95 % confidence limits: 1.3 - 20 mu g.L-1) and 0.09 mg.L-1 (95 % confidence limits: 0.011 - 0.755 mg.L-1), respectively. CONCLUSION: Trichobitacin is a novel ribosome-inactivating protein with anti-HIV-l activity.