Search results for "Molecular chemistry"
showing 10 items of 1103 documents
Polyether-bridged cyclophanes incorporating bisphenol A units as neutral receptors for quats: synthesis, molecular structure and binding properties
2001
Two novel neutral polyoxyethylene bridged cyclophanes (2a and 2b) incorporating bisphenol A units were synthesized and characterized by means of x-ray crystal structure determination. The binding properties of 2a and 2b toward tetramethylammonium, N-methylpyridinium, and acetylcholine cations were evaluated by means of 1H NMR spectroscopy. Consistent with indications provided by the molecular structure, the cavity in the basket-like cyclophanes is large enough to accommodate the given guest cations conveniently. Circumstantial evidence was obtained that 1,1,2,2-tetrachloroethane is too large to enter the cavity of the smaller cyclophane 2a, but can be included in the cavity of the larger cy…
Sports activities in the natural environment: its representation in physical education textbooks in primary school
2017
El objeto de esta investigación es analizar las actividades deportivas realizadas en el medio natural representadas en los libros de texto de Educación Física (EF) en la etapa de Educación Primaria (EP), publicados en la Ley Orgánica 2/2006, de 3 de mayo, de Educación (LOE). Se analizan 4339 imágenes, recogidas en 44 libros de texto, pertenecientes a ocho editoriales españolas. Para el análisis de contenido de las imágenes se utilizó la herramienta SAIMEF (Sistema de Análisis de las Imágenes de Educación Física), elaborada ad hoc. La prueba piloto, el panel de expertos y la triangulación con varios observadores fueron algunos de los criterios de cientificidad que avalaron dicha herramienta.…
MuLiMs-MCoMPAs: A Novel Multiplatform Framework to Compute Tensor Algebra-Based Three-Dimensional Protein Descriptors
2019
This report introduces the MuLiMs-MCoMPAs software (acronym for Multi-Linear Maps based on N-Metric and Contact Matrices of 3D Protein and Amino-acid weightings), designed to compute tensor-based 3D protein structural descriptors by applying two- and three-linear algebraic forms. Moreover, these descriptors contemplate generalizing components such as novel 3D protein structural representations, (dis)similarity metrics, and multimetrics to extract geometrical related information between two and three amino acids, weighting schemes based on amino acid properties, matrix normalization procedures that consider simple-stochastic and mutual probability transformations, topological and geometrical…
The Two‐Step Spin Conversion in a Supramolecular Triple Helicate Dinuclear Iron(II) Complex Studied by Mössbauer Spectroscopy
2006
The triple helicate dinuclear iron(II) complex, [Fe-2(L)(3)](ClO4)(4)center dot 2H(2)O (1), previously reported by Tuna et al. (Chem. Eur. J. 2004, 10, 5737), was prepared and characterised by detailed SQUID and Fe-57 Mbssbauer measurements. Compound 1 exhibits a thermochromic two-step spin conversion at T-SC((1)) ca. 240 K and T-SC((2)) ca. 120 K, but does not switch its spin state further below 20 K as proven by Mossbauer spectroscopy. The sharp variation of the susceptibility below 20 K is due to zero-field splitting of the remaining iron(II) high-spin species. Applied field Fe-57 Mossbauer spectroscopy experiments at 4.2 K indicate that the gradual thermal spin conversion from [HS-HS] p…
Supramolecular diversity and magnetic properties of novel heterometallic Cu(II)/Cr(III) complexes prepared from copper powder, Reineckes salt and eth…
2009
Abstract Three novel heterometallic complexes [Cu(en) 2 Cr(NCS) 4 (NH 3 ) 2 ][Cr(NCS) 4 (NH 3 ) 2 ] · 6dmf ( 1 ), [Cu(en) 2 Cr(NCS) 4 (NH 3 ) 2 ](OAc) ( 2 ) and [{Cu(en) 2 } 3 {Cr(NCS) 4 (NH 3 ) 2 } 2 (NCS) 2 ](NCS) 2 ( 3 ) have been synthesized in a one-pot reaction from copper powder, Reineckes salt, NH 4 X [X − = OAc − ( 2 ), NCS − ( 3 )] in a dmf ( 1 ) or CH 3 CN ( 2 , 3 ) solution of ethylenediamine (en). X-ray studies showed that 1 and 2 consist of cationic polymeric chains, formed by Cu ( en ) 2 2 + and Cr ( NCS ) 4 ( NH 3 ) 2 - building blocks that bridged through thiocyanate anions. In both complexes, distinct hydrogen bonds are present and serve to increase the dimensionality of …
Composition of essential oil of lemon thyme (Thymus × citriodorus) at different hydrodistillation times.
2018
Distillation time can both to optimise the production and to engineer the composition of essential oil in essential oil bearing plants. Purpose of this study was to evaluate the effect of duration of hydrodistillation on composition of essential oil of Thymus × citriodorus, the natural source of commercially important geraniol and citral, a component with valuable biological properties. Essential oils were isolated by hydrodistillation at different distillation times and analysed by GC/MS analytical methods. Increase in percentage of essential oil during all hydrodistillation time gradient was uneven. Elongation of hydrodistillation time decreased percentages of monoterpenes but increased p…
Preservation of vitamins content in Cuccìa using an innovative method of processing
2019
Cuccìa is a traditional Sicilian food prepared by boiling whole durum wheat kernels, in water, for many hours. This process destroys the vitamins E and B contents of crude kernels. It was rated a method to prepare the Cuccìa, preserving the vitamin content. Four varieties of durum wheat were processed comparing the traditional cooking method (TR-boiling for 5/6 hours), and an innovative one (IN-grains scarification, germination, and cooking at 50 °C for 2 hours). On soups obtained the content of biotin, niacin and α-amylase activity were determined. ANOVA showed the cooking method influences biotin and niacin content having values from 0.56 and 0.72 ng ml−1 (raw grain) and values close to 0…
The Effect of Calcium on the Cohesive Strength and Flexural Properties of Low-Methoxyl Pectin Biopolymers.
2019
Abstract: Pectin binds the mesothelial glycocalyx of visceral organs, suggesting its potential role as a mesothelial sealant. To assess the mechanical properties of pectin films, we compared pectin films with a less than 50% degree of methyl esterification (low-methoxyl pectin, LMP) to films with greater than 50% methyl esterification (high-methoxyl pectin, HMP). LMP and HMP polymers were prepared by step-wise dissolution and high-shear mixing. Both LMP and HMP films demonstrated a comparable clear appearance. Fracture mechanics demonstrated that the LMP films had a lower burst strength than HMP films at a variety of calcium concentrations and hydration states. The water content also influe…
Elucidating the aryl hydrocarbon receptor antagonism from a chemical-structural perspective.
2020
The aryl hydrocarbon receptor (AhR) plays an important role in several biological processes such as reproduction, immunity and homoeostasis. However, little is known on the chemical-structural and physicochemical features that influence the activity of AhR antagonistic modulators. In the present report, in vitro AhR antagonistic activity evaluations, based on a chemical-activated luciferase gene expression (AhR-CALUX) bioassay, and an extensive literature review were performed with the aim of constructing a structurally diverse database of contaminants and potentially toxic chemicals. Subsequently, QSAR models based on Linear Discriminant Analysis and Logistic Regression, as well as two tox…
Cytotoxic neo-clerodane diterpenes from Stachys aegyptiaca
2018
Abstract Two new E/Z neo-clerodane diterpene isomers, trivially named stachaegyptin D (1) and E (2), together with known compounds, stachysolon monoacetate (3) and stachysolon diacetate (4), were isolated from an organic-solvent extract of the medicinal herb Stachys aegyptiaca. Structures were elucidated by a combination of spectroscopic methods, including HREIMS, 1H, 13C, DEPT, and 2D NMR analysis, as well as, first time X-ray analysis for stachysolone (3). All isolated metabolites showed some activity against the human hepatocellular cell line, HepG2. Compound 4 was the most active with an IC50 of 59.5 μM.