Espectroscopía Raman Intensificada por Superficie (SERS) en la identificación de microorganismos que producen biodeterioro: patrimonio edificado con arquitectura en tierra, Vale Histórico Paulista (São Paulo, Brasil)

El objetivo de este trabajo es presentar resultados obtenidos mediante análisis por espectroscopía Raman intensificada por superficie (SERS) como herramienta novedosa para la identificación taxonómica de hongos a partir de biofilms formados en paredes de arquitectura en tierra (“pau-a-pique”, “taipa de pilão”, y adobe), en edificaciones históricas del Vale Histórico de São Paulo, representativas del período colonial brasileño, Con el objetivo de abrir la posibilidad de clasificación de hongos mediante SERS, se seleccionaron colonias puras que fueron previamente aislados de las paredes de tierra e identificados por taxonomía clásica y biología molecular. Los géneros estudiados fueron: Trichoderma, Cladosporium, Aspergillus, Neurospora, Fusarium y Penicillium. Las colonias fueron cultivadas en PDA sólido. Se realizaron extractos en acetato de etilo que fueron mezclados con nanopartículas de oro en suspensión coloidal. Se observaron bandas características de grupos funcionales en la región entre 600 y 1800 cm-1 que presentaron diferencias para cada género. Análisis estadísticos de PCA y HCA mostraron relaciones que permitieron hacer asociaciones por género. Este trabajo es el primer reporte de comunidades microbianas a partir de paredes hechas con técnicas de arquitectura en tierra con el uso de Espectroscopía SERS

Correlation between SERS of Pyridine and Electrochemical Response of Silver Electrodes in Halide-Free Alkaline Solutions

Surface-enhanced Raman scattering (SERS) of pyridine (Py) on Ag electrodes in alkaline solutions free of halide ions was obtained at 25°C as a function of the applied potential. The Ag surface was activated for SERS through repetitive oxidation-reduction cycles (ORC), the effect being dependent on the electrochemical electrode history. The SERS effect was correlated to the activation for the hydrogen evolution reaction (HER), which can be obtained by means of potentiodynamic as well as potentiostatic procedures. The maximum SERS activity was achieved at potentials near the potential of zero charge (pzc) of polycrystalline Ag and appeared to be related to the maximum observed in the roughness factor vs potential curve. These results can be interpreted through the formation of a new uniform globular overlayer structure on the electroreduced Ag surface, which apparently exhibits a certain degree of preferred crystallographic orientation. Three well-defined potential regions can be distinguished for the complex competitive interactions between H2O, OH- ion, and Py with the new Ag electrode surface.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Correlation between SERS of Pyridine and Electrochemical Response of Silver Electrodes in Halide-Free Alkaline Solutions

Surface-enhanced Raman scattering (SERS) of pyridine (Py) on Ag electrodes in alkaline solutions free of halide ions was obtained at 25°C as a function of the applied potential. The Ag surface was activated for SERS through repetitive oxidation-reduction cycles (ORC), the effect being dependent on the electrochemical electrode history. The SERS effect was correlated to the activation for the hydrogen evolution reaction (HER), which can be obtained by means of potentiodynamic as well as potentiostatic procedures. The maximum SERS activity was achieved at potentials near the potential of zero charge (pzc) of polycrystalline Ag and appeared to be related to the maximum observed in the roughness factor vs potential curve. These results can be interpreted through the formation of a new uniform globular overlayer structure on the electroreduced Ag surface, which apparently exhibits a certain degree of preferred crystallographic orientation. Three well-defined potential regions can be distinguished for the complex competitive interactions between H2O, OH- ion, and Py with the new Ag electrode surface.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

On the correlation between electronic intramolecular delocalization and Au-S bonding strength of ruthenium tetraammine SAMs

Trans-[Ru(L)(NH3)4(L’)](PF6)n type complexes, where L = 4-cyanopyridine (CNpy), NCS-, CN-, and L’ = CNpy, 1,4-dithiane (1,4-dt), 4-mercaptopyridine (pyS) and thionicotinamide (tna), were synthesized and characterized. SAMs on gold of the complexes containing sulfur were studied by reductive desorption and SERS spectroscopy. Depending on the nature of L’, the withdrawing capability of the CNpy ligand is strong enough to partially oxidize the ruthenium atom and, as a consequence, delocalize the s electronic density from the trans located ligand. The reductive desorption results showed that the stability of the SAMs is directly related to this effect

Let’s not forget tautomers

A compound exhibits tautomerism if it can be represented by two structures that are related by an intramolecular movement of hydrogen from one atom to another. The different tautomers of a molecule usually have different molecular fingerprints, hydrophobicities and pKa’s as well as different 3D shape and electrostatic properties; additionally, proteins frequently preferentially bind a tautomer that is present in low abundance in water. As a result, the proper treatment of molecules that can tautomerize, ~25% of a database, is a challenge for every aspect of computer-aided molecular design. Library design that focuses on molecular similarity or diversity might inadvertently include similar molecules that happen to be encoded as different tautomers. Physical property measurements might not establish the properties of individual tautomers with the result that algorithms based on these measurements may be less accurate for molecules that can tautomerize—this problem influences the accuracy of filtering for library design and also traditional QSAR. Any 2D or 3D QSAR analysis must involve the decision of if or how to adjust the observed Ki or IC50 for the tautomerization equilibria. QSARs and recursive partitioning methods also involve the decision as to which tautomer(s) to use to calculate the molecular descriptors. Docking virtual screening must involve the decision as to which tautomers to include in the docking and how to account for tautomerization in the scoring. All of these decisions are more difficult because there is no extensive database of measured tautomeric ratios in both water and non-aqueous solvents and there is no consensus as to the best computational method to calculate tautomeric ratios in different environments

Identification of a Lacosamide Binding Protein Using an Affinity Bait and Chemical Reporter Strategy: 14-3-3 ζ

We have advanced a useful strategy to elucidate binding partners of ligands (drugs) with modest binding affinity. Key to this strategy is attaching to the ligand an affinity bait (AB) and a chemical reporter (CR) group, where the AB irreversibly attaches the ligand to the receptor upon binding and the CR group is employed for receptor detection and isolation. We have tested this AB&CR strategy using lacosamide ((R)-1), a low-molecular-weight antiepileptic drug. We demonstrate that using a (R)-lacosamide AB&CR agent ((R)-2) 14-3-3 ζ in rodent brain soluble lysates is preferentially adducted, adduction is stereospecific with respect to the AB&CR agent, and adduction depends upon the presence of endogenous levels of the small molecule metabolite xanthine. Substitution of lacosamide AB agent ((R)- 5) for (R)-2 led to the identification of the 14-3-3 ζ adduction site (K120) by mass spectrometry. Competition experiments using increasing amounts of (R)-1 in the presence of (R)-2 demonstrated that (R)-1 binds at or near the (R)-2 modification site on 14-3-3 ζ. Structure-activity studies of xanthine derivatives provided information concerning the likely binding interaction between this metabolite and recombinant 14-3-3 ζ. Documentation of the 14-3-3 ζ-xanthine interaction was obtained with isothermal calorimetry using xanthine and the xanthine analogue 1,7-dimethylxanthine

An adaptive, competence based, approach to serious games sequencing in technology enhanced learning

We present a platform for Technology Enhanced Learning, allowing the learner to follow a path of game applications towards a learning objective. The path is determined by the learner, by selecting each time the next game of her choosing. The games are defined by teachers and experts, or even imported as web resources: they are associated to the system through suitable metadata, that express their pedagogical meaning. The system's interface allows the student to navigate the repository of learning games (organized as a graph) and see among them those that she can select to undertake, and those that are not yet affordable. Whether a game is affordable, at a given moment, is determined by comparing the Student Model with the game's specification. In conclusion, the path of learning activities followed by the learner is built interactively, by the learner, according to learner's choice and the system's pedagogical guidance. The system has not yet been experimented in a real class: we report about its design and implementation, and provide the reader with some simulated applications showing the system's behaviour

FT-Raman investigation of biodegradable polymers: Poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

This work presents a FT-Raman study (lambda(0) = 1064 nm) of naturally occurring polyester poly[(R)-3-hydroxybutyrate] (PHB) and its copolymer poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyvalerate] (PHBV) with 5,8 and 12 mol % of HV (hydroxyvalerate). The FT-Raman spectra of films indicate that full width at half height of the band centered at 1725 cm(-1) and relative intensity of bands at 1443 and 1458 cm(-1) can be use to estimate the crystalline degree in film samples. The similarity between Raman spectra of molten PHB and PHBV and theirs CDCl(3) solutions suggested that molten polymers present similar conformation than polymers in solution. Raman data of these samples showed that bands at 1220, 1402, 1725, 2998 and 3009 cm(-1) are due to crystalline helical structure and the bands at 1453, 1740, 2881, 2938 and 2990 cm(-1) are originated from disordered domains. It is shown that composition of PHBV samples can be estimated by analyzing the ratio of the intensity of the bands at 2938 cm(-1) (nu C-H) and 1740 cm(-1) (nu C=O) in the spectra of solutions and of bands at 1354 (wCH(2)) and 1740 cm(-1) (nu C=O) in spectra of molten polymers. (C) 2010 Elsevier B.V. All rights reserved