Search results for "AROMA"

Understanding the ring current effects on magnetic shielding of hydrogen and carbon nuclei in naphthalene and anthracene

2008

The local response to an external magnetic field normal to the molecular plane of naphthalene and anthracene was investigated via current density and magnetic shielding density maps. The Biot-Savart law shows that the deshielding caused by pi-ring currents in naphthalene is stronger for alpha- than for beta-protons due to geometrical factors. The shielding tensor of the carbon nuclei in both molecules is strongly anisotropic and its out-of-plane component determines the up-field chemical shift of (13)C in nuclear magnetic resonance spectra. The pi-ring currents flowing beyond the C-skeleton in front of a probe carbon nucleus, and on remote parts of the molecular perimeter, yield positive co…

Intramolecular electronic excitation energy transfer in donor∕acceptor dyads studied by time and frequency resolved single molecule spectroscopy

2008

Electronic excitation energy transfer has been studied by single molecule spectroscopy in donor/acceptor dyads composed of a perylenediimide donor and a terrylenediimide acceptor linked by oligo(phenylene) bridges of two different lengths. For the shorter bridge (three phenylene units) energy is transferred almost quantitatively from the donor to the acceptor, while for the longer bridge (seven phenylene units) energy transfer is less efficient as indicated by the occurrence of donor and acceptor emission. To determine energy transfer rates and efficiencies at the single molecule level, several methods have been employed. These comprise time-correlated single photon counting techniques at r…

Recent advances in computational design of potent aromatase inhibitors: open-eye on endocrine-resistant breast cancers.

2019

Introduction: The vast majority of breast cancers (BC) are estrogen receptor positive (ER+). The most effective treatments to fight this BC type rely on estrogen deprivation therapy, by inhibiting the aromatase enzyme, which performs estrogen biosynthesis, or on blocking the estrogens signaling path via modulating/degrading the estrogen's specific nuclear receptor (estrogen receptor-?, ER?). While being effective at early disease stage, patients treated with aromatase inhibitors (AIs) may acquire resistance and often relapse after prolonged therapies. Areas covered: In this compendium, after an overview of the historical development of the AIs currently in clinical use, and of the computati…

Is the chromanol head group of vitamin E nature's final truth on chain-breaking antioxidants?

2012

AbstractTocopherol is believed to be the most potent naturally occurring chain-breaking antioxidant. Hence, its refined phenolic head group chromanol may represent an optimum evolutionary solution to the problem of free-radical chain reactions in the lipid bilayer. To test the universal validity of this assumption beyond phenolic head groups, we have synthesized aromatic amine analogues of vitamin E and trolox with otherwise closely matching physicochemical properties: NH-toc and NH-trox. We have found that NH-toc and NH-trox were significantly more potent free radical scavengers, lipid peroxidation inhibitors and cytoprotective agents than their phenolic templates, tocopherol and trolox. I…

Effect of ferulic acid and α-tocopherol antioxidants on properties of sodium caseinate edible films

2011

Edible films, based on sodium caseinate containing three different concentrations of ferulic acid or alpha-tocopherol (20, 40 and 60 mg/g sodium caseinate), were obtained in order to evaluate the effect of these compounds on properties of the caseinate matrices. Special emphasis was placed on their effect on the films' oxygen barrier properties, which are decisive in the prevention of the oxidation of foods containing lipids. Films were characterized as to their tensile, optical and surface properties as well as their barrier properties to water vapor, oxygen and aroma compounds (n-hexanal and n-hexanol). Ferulic acid was more efficient at reducing oxygen and n-hexanal permeability than alp…

Polycyclic aromatic hydrocarbons and trace metal contamination of coastal sediment and biota from Togo

2011

The state of contamination of tropical environments, particularly in Africa, remains a relatively under explored subject. Here, we determined polycyclic aromatic hydrocarbon (PAH) and trace metal concentrations in coastal sediment and biota samples (fish and mussels) from Togo (West Africa). In the sediments, the ∑21 PAH concentrations ranged from4 ng g(-1) to 257 ng g(-1), averaging 92 ng g(-1). Concentration ratios of low molecular weight PAHs (2-3 rings) versus high molecular weight PAHs (≥4 rings) were always lower than 1 (ranging from 0.08 to 0.46) indicating that high molecular weight PAHs were dominant in all sediment samples, and that PAHs originated mainly from anthropogenic combus…

The possibilities of using the aspen poplar seeds (Populus tremula L.) for the purpose of removing monoaromatic hydrocarbons from an aqueous solution

2018

Sorption of oil-related products (including mainly the propellants) is the very basic process that counteracts spreading these types of pollution into environment. Plenty of synthetic substances are used as sorbents for binding organic compounds (including the monoaromatic hydrocarbons) both from the surface and underground waters. The aim of this paper is to present results of the research on the possibilities of using the aspen poplar (Populus tremula L.) seeds as a sorbent of monoaromatic hydrocarbons from an aqueous solution. In order to increase sorption capacity, the seeds biomass was submitted for the process of mercerizing in diversified time and temperature in water and the NaOH so…

Complexation and Extraction of PAHs to the Aqueous Phase with a Dinuclear Pt II Diazapyrenium‐Based Metallacycle

2010

New palladium and platinum metallacycles have been synthesized by reaction between a 2,7-diazapyrenium-based ligand and Pd(II) and Pt(II) complexes. The inclusion complexes between the metallacycles and polycyclic aromatic hydrocarbons (PAHs) in CD(3)NO(2) and D(2)O were studied by NMR spectroscopy. The structures of the inclusion complexes of the Pt metallacycle as host with pyrene, phenanthrene, and triphenylene were confirmed by single crystal X-ray crystallography. The association constants between the Pt metallacycle and the selected PAHs were determined in CH(3)CN following the characteristic charge-transfer band displayed in their UV/Vis absorption spectrum. Although in aqueous solut…

Corrigendum to “Influence of temperature and NaCl on the release in aqueous liquid media of aroma compounds encapsulated in edible films” [Journal of…

2012

Effects of the nature and concentration of substrates in aqueous solutions on the solubility of aroma compounds

2005

The solubility of nine aroma compounds (acetone, 2-butanone, 2-hexanone, 2-octanone, ethyl acetate, ethyl butanoate, ethyl hexanoate, n-hexanal, and n-hexanol) in both water and various aqueous solutions was measured at 25 °C using the mutual solubility method. The aqueous solutions consisted of sucrose, glucose, sorbitol, glycerol, polyethylene glycol 200, or maltodextrins at different concentrations. Aroma solubility in water decreased with increased hydrophobicity. For aroma molecules which have the same number of carbon atoms in their structure, aqueous solubility decreased as follows: aldehyde > methyl ketone > alcohol > ethyl ester. When using a group contribution method, the estimate…