Evolution of grape polyphenol oxidase activity and phenolic content during maturation and vinification

The activity of polyphenol oxidase (PPO) and content of phenolic compounds were followed during the maturation in two varieties of wine grapes grown in south-eastern Spain and during vinification at different sulphur dioxide concentrations.Both cresolase and catecholase activities (measured at pH 7.0 and 4.5, respectively) increased throughout the studied period and the content of phenolic compounds decreased rapidly when expressed as concentration (mg gallic acid/g total fresh weight), while when expressed as total amount per berry (mg/berry) it remained constant. During wine production, the enzyme activity was highest immediately after crushing of the fresh grapes and was not detected at the end of the fermentation process. The phenolic content also decreased during vinification to a constant level depending on the S02 level used

Activation of H-H, HO-H, C(sp2)-H, C(sp3)-H, and RO-H bonds by transition-metal frustrated lewis pairs based onon M/N (M = Rh, Ir) couples

Reaction of the dimers (Cp*MCl)2(µ-Cl)2] (Cp* = 5-C5Me5) with Ph2PCH2CH2NC(NH(p-Tolyl))2 (H2L) in the presence of NaSbF6 affords the chlorido complexes Cp*MCl(¿2N, P-H2L)]SbF6] (M = Rh, 1; Ir, 2). Upon treatment with aqueous NaOH, solutions of 1 and 2 yield the corresponding complexes Cp*M(¿3N, N', P-HL)]SbF6] (M = Rh, 3; Ir, 4) in which the ligand HL presents a fac ¿3N, N', P coordination mode. Treatment of THF solutions of complexes 3 and 4 with hydrogen gas, at room temperature, results in the formation of the metal hydrido-complexes Cp*MH(¿2N, P-H2L)]SbF6] (M = Rh, 5; Ir, 6) in which the N(p-Tolyl) group has been protonated. Complexes 3 and 4 react with deuterated water in a reversible fashion resulting in the gradual deuteration of the Cp* group. Heating at 383 K THF/H2O solutions of the complexes 3 and 4 affords the orthometalated complexes Cp*M(¿3C, N, P-H2L-H)]SbF6] M = Rh, 7; Ir, 8, H2L-H = Ph2PCH2CH2NC(NH(p-Tolyl))(NH(4-C6H3Me))], respectively. At 333 K, complexes 3 and 4 react in THF with methanol, primary alcohols, or 2-propanol giving the metal-hydrido complexes 5 and 6, respectively. The reaction involves the acceptorless dehydrogenation of the alcohols at a relatively low temperature, without the assistance of an external base. The new complexes have been characterized by the usual analytical and spectroscopic methods including the X-ray diffraction determination of the crystal structures of complexes 1-5, 7, and 8. Notably, the chlorido complexes 1 and 2 crystallize both as enantiopure conglomerates and as racemates. Reaction mechanisms are proposed based on stoichiometric reactions, nuclear magnetic resonance studies, and X-ray crystallography as well as density functional theory calculations. © 2022 The Authors. Published by American Chemical Society

¿Qué investigación didáctica en el aula de física se publica en España? Una revisión crítica de la última década para el caso de educación secundaria

Se presenta un estudio exploratorio y descriptivo sobre la investigación didáctica publicada en España durante la última década relativa a la enseñanza de la física en educación secundaria. Al centrar la atención en aquellos estudios que analizan algún aspecto del proceso de enseñanza-aprendizaje en el aula, se obtiene que estos constituyen una minoría en el conjunto de la bibliografía consultada. Se encuentra también que la autoría de profesorado de secundaria en los estudios sobre didáctica de la física consultados es relativamente baja. Asimismo, en los estudios predomina un enfoque de la enseñanza de la física orientado por contenidos disciplinares que no sintonizan con los planteamientos basados en el desarrollo de competencias. Todo ello revela cierta distancia entre investigación y práctica en la enseñanza de la física.An explorative and descriptive study about educational research concerning physics teaching in secondary education, published in Spain during the last decade, is presented. When focusing on those studies oriented towards the analysis of some aspects of the teaching/learning processes within classroom, it is found that they constituted a minority in the frame of the consulted literature. It is also found that the number of studies on physics education authored by secondary teachers is relatively low. Likewise, an approach to physics teaching guided by disciplinary contents is predominant in these studies, which is not in tune with those approaches based on the development of competences. All this reveals a certain disconnection between research and practice in physics education

Cobalt (II) environment characterization in sol-gel thermochromic sensors

Optical absorption and magnetic properties of silica sol-gel monoliths doped with cobalt starting from different precursors and water/1-propanol molar ratios are investigated. Structural characterization of the sol-gel by X-ray absorption near-edge structure (XANES) spectroscopy and extended X-ray absorption fine structure (EXAFS) spectroscopy corroborate, that oxidising state of cobalt is Co^(2+). Furthermore, the Co^(2+) first neighbors are O atoms displaying a temperature transition from octahedral to tetrahedral coordination. The doped monoliths show thermochromic sensor activity ranging from 10 to 50⁰ C, which is related to the environment of Co^(2+) ions. The magnetic susceptibility also varies with Co^(2+) ions environment due to changes in the orbital contribution to the magnetic moment. Thus, we achieve a better understanding about environment of the Co^(2+) ions in the gel matrix and explain their reversible temperature behaviour in spite of the rigid state of the host matrix

A genomic approach highlights common and diverse effects and determinants of susceptibility on the yeast Saccharomyces cerevisiae exposed to distinct antimicrobial peptides

<p>Abstract</p> <p>Background</p> <p>The mechanism of action of antimicrobial peptides (AMP) was initially correlated with peptide membrane permeation properties. However, recent evidences indicate that action of a number of AMP is more complex and involves specific interactions at cell envelopes or with intracellular targets. In this study, a genomic approach was undertaken on the model yeast <it>Saccharomyces cerevisiae </it>to characterize the antifungal effect of two unrelated AMP.</p> <p>Results</p> <p>Two differentiated peptides were used: the synthetic cell-penetrating PAF26 and the natural cytolytic melittin. Transcriptomic analyses demonstrated distinctive gene expression changes for each peptide. Quantitative RT-PCR confirmed differential expression of selected genes. Gene Ontology (GO) annotation of differential gene lists showed that the unique significant terms shared by treatment with both peptides were related to the cell wall (CW). Assays with mutants lacking CW-related genes including those of MAPK signaling pathways revealed genes having influence on sensitivity to peptides. Fluorescence microscopy and flow cytometry demonstrated PAF26 interaction with cells and internalization that correlated with cell killing in sensitive CW-defective mutants such as Δ<it>ecm33 </it>or Δ<it>ssd1</it>. GO annotation also showed differential responses between peptides, which included ribosomal biogenesis, <it>ARG </it>genes from the metabolism of amino groups (specifically induced by PAF26), or the reaction to unfolded protein stress. Susceptibility of deletion mutants confirmed the involvement of these processes. Specifically, mutants lacking <it>ARG </it>genes from the metabolism of arginine pathway were markedly more resistant to PAF26 and had a functional CW. In the deletant in the arginosuccinate synthetase (<it>ARG1</it>) gene, PAF26 interaction occurred normally, thus uncoupling peptide interaction from cell killing. The previously described involvement of the glycosphingolipid gene <it>IPT1 </it>was extended to the peptides studied here.</p> <p>Conclusions</p> <p>Reinforcement of CW is a general response common after exposure to distinct AMP, and likely contributes to shield cells from peptide interaction. However, a weakened CW is not necessarily indicative of a higher sensitivity to AMP. Additional processes modulate susceptibility to specific peptides, exemplified in the involvement of the metabolism of amino groups in the case of PAF26. The relevance of the response to unfolded protein stress or the sphingolipid biosynthesis, previously reported for other unrelated AMP, was also independently confirmed.</p

Detección de funcionamiento diferencial del ítem en indicadores conductuales de formas paralelas

Background: Despite the crucial importance of the notion of parallel forms within Classical Test Theory, the degree of parallelism between two forms of a test cannot be directly verified due to the unobservable nature of true scores. We intend to overcome some of the limitations of traditional approaches to analyzing parallelism by using the Differential Item Functioning framework. Method: We change the focus on comparison from total test scores to each of the items developed during test construction. We analyze the performance of a single group of individuals on parallel items designed to measure the same behavioral criterion by several DIF techniques. The proposed approach is illustrated with a dataset of 527 participants that responded to the two parallel forms of the Attention Deficit-Hyperactivity Disorder Scale (Caterino, Gómez-Benito, Balluerka, Amador-Campos, & Stock, 2009). Results: 12 of the 18 items (66.6%) show probability values associated with the Mantel χ2 statistic of less than .01. The standardization procedure shows that half of DIF items favoured Form A and the other half Form B. Conclusions: The “differential functioning of behavioral indicators” (DFBI) can provide unique information on parallelism between pairs of items to complement traditional analysis of equivalence between parallel test forms based on total scores.Antecedentes: a pesar de la importancia crucial del concepto de formas paralelas en la Teoría Clásica de los Tests, el grado de paralelismo entre dos formas paralelas no puede comprobarse directamente debido al carácter inobservable de las puntuaciones verdaderas. Nuestra propuesta pretende superar algunas de las limitaciones de los métodos tradicionales utilizando el esquema del Funcionamiento Diferencial del Item. Método: cambiamos el objeto de la comparación de las puntuaciones totales a cada uno de los ítems individuales. Analizamos las puntuaciones de un único grupo de participantes en ítems paralelos diseñados para medir los mismos criterios comportamentales. Ejemplificamos la propuesta con las respuestas de 527 participantes a las dos formas paralelas de la “Attention Deficit-Hyperactivity Disorder Scale” (Caterino, Gómez-Benito, Balluerka, Amador-Campos, & Stock, 2009).Resultados: 12 de los 18 ítems (66,6%) muestran valores de probabilidad asociados con el estadístico Mantel χ2 menores de .01. El procedimiento de Estandarización muestra que la mitad de los ítems con DIF favorecen a la Forma A y la otra mitad a la Forma B. Conclusiones: el procedimiento “differential functioning of behavioral indicators” (DFBI) puede aportar información única sobre el paralelismo entre parejas de ítems complementando el análisis tradicional de la equivalencia de formas paralelas.This study was partially funded by the Andalusia Regional Government under the Excellent Research Fund (Project nº SEJ- 6569, Project nº SEJ-5188), and the Agency for the Management of University and Research Grant of the Government of Catalonia (2014 SGR-1139)