Search results for " infrared spectroscopy"
showing 10 items of 438 documents
Stopped-flow Fourier-transform infra-red spectrometric speciation of glycolic and lactic acids in cosmetic formulations
2001
The dermatological activity of cosmetic formulations containing alpha-hydroxyacids depends on their different chemical forms, and it is therefore useful to determine these species in the finished products. In the present report a new procedure for studying the protonation equilibria of glycolic and lactic acids by stopped-flow Fourier-transform infra-red (FTIR) spectrometry is described. The procedure was validated for use in the speciation of glycolic and lactic acids in cosmetic formulations, with preferential attention given to glycolic acid, which is the most widely used. Species of these alpha-hydroxyacids can be approximately determined at different pHs and the total content of each a…
Determination of lecithin and soybean oil in dietary supplements using partial least squares-Fourier transform infrared spectroscopy.
2008
Lecithin and soybean oil in dietary supplements were determined by Fourier transform infrared spectrometry transmission measurements in dichloromethane in combination with a partial least squares (PLS) regression. Two different PLS models were developed, using 16 synthetic mixtures of analytes in dichloromethane, making measurements in the spectral range from 931.8 to 1252.3 cm(-1) for lecithin and from 911.4 to 1246.9 cm(-1) and 1695.3 to 1774.5 cm(-1) for soybean oil. Seven products from the Spanish market with lecithin concentrations between 21.1% and 99.1% and soybean oil concentrations between 0% and 37.2% were analyzed by the proposed method and the data was compared to a chromatograp…
Glucagon fibril polymorphism reflects differences in protofilament backbone structure
2010
Amyloid fibrils formed by the 29-residue peptide hormone glucagon at different concentrations have strikingly different morphologies when observed by transmission electron microscopy. Fibrils formed at low concentration (0.25 mg/mL) consist of two or more protofilaments with a regular twist, while fibrils at high concentration (8 mg/mL) consist of two straight protofilaments. Here, we explore the structural differences underlying glucagon polymorphism using proteolytic degradation, linear and circular dichroism, Fourier transform infrared spectroscopy (FTIR), and X-ray fiber diffraction. Morphological differences are perpetuated at all structural levels, indicating that the two fibril class…
Spectroscopic and electrochemical study of interactions between DNA and different salts of 1,4-dihydropyridine AV-153
2020
1,4-dihydropyridines (1,4-DHP) possess important biochemical and pharmacological properties, including antimutagenic and DNA-binding activity. The latter activity was first described for water-soluble 1,4-DHP with carboxylic group in position 4, the sodium salt of the 1,4-DHP derivative AV-153 among others. Some data show the modification of physicochemical properties and biological activities of organic compounds by metal ions that form the salts. We demonstrated the different affinity to DNA and DNA-protecting capacity of AV-153 salts, depending on the salt-forming ion (Na, K, Li, Rb, Ca, Mg). This study aimed to use different approaches to collate data on the DNA-binding mode of AV-153-N…
Thermal aggregation and ion-induced cold-gelation of bovine serum albumin
2009
Protein cold-gelation has recently received particular attention for its relevance in bio and food technology. In this work, we report a study on bovine serum albumin cold-gelation induced by copper or zinc ions. Metal-induced cold-gelation of proteins requires two steps: during the first one, the heat treatment causes protein partial unfolding and aggregation; then, after cooling the solution to room temperature, gels are formed upon the addition of metal ions. The thermally induced behaviour has been mainly investigated through different techniques: Fourier transform infrared (FTIR) spectroscopy, circular dichroism, dynamic light scattering (DLS) and rheology. Data have shown that the agg…
Evaluation of sewage sludge-based compost by FT-IR spectroscopy
2006
The aerobic batch composting fermentations of sewage sludge with wood chips and maturity compost as co-composting additives were carried out in an open type lab-scale reactor. Fourier transform infrared spectroscopy (FT-IR) spectroscopy was used to monitor the composting process, evaluate the degradation rate and thus determine the maturity. Although the composition of the input mixture strongly affects the shape of the infrared (IR) spectra, typical bands of components can be selected and used to follow the composting process. The appearance, shape and intensity of the nitrate band at 1384 cm 1 was well pronounced and evident for a sewage sludgebased compost maturity. An increase of the pe…
Electrochemical and spectroscopic study on thiolation of polyaniline
2013
Abstract Polyaniline (PANI) is a conducting polymer, easily synthesized and lucrative for many electrochemical applications like ion-selective sensors and biosensors. Thiolated molecules, including biological ones, can be bound by nucleophilic attachment to the polyaniline backbone. These covalently bound thiols add functionality to PANI, but also cause changes in the electrochemical properties of PANI. Polyaniline studied in this work was electropolymerized on glassy carbon electrodes. 2-Mercaptoethanol (MCE) and 6-(ferrocenyl)hexanethiol (FCHT) were used as the thiols to form functionalized films. The films were characterized by cyclic voltammetry (CV), ex situ FTIR and Raman spectroscopi…
The first silver(I) nitrate π-complexes with unsaturated organosilicons: Synthesis and structural characterization of [Ag(DADPS)xNO3] (DADPS=diallyld…
2011
Abstract Tetraethylene glycol dimethyl ether (tetraglyme) was used for the first time to induce the activation of silver nitrate resulting in the step-by-step formation of complexes with diallyldiphenylsilane (DADPS). Two crystal compounds of this series were examined by FTIR spectroscopy and X-ray diffraction. The analysis of the obtained data showed that the Ag (C C) η 2 -interaction is involved in the synergistic effect of intra and intermolecular forces. In particular the interlayer π–π stacking interactions promoted by asymmetric weak Ag C(phenyl) bond have a significant influence on the thermal behavior and stability of the synthesized products. It was also found that a decrease of si…
Quantitative analysis of mixtures of metal-carbonyl complexes by Fourier-transform infrared spectroscopy: application to the simultaneous double immu…
1996
Abstract The feasibility of a double immunoassay of haptens by the nonisotopic carbonyl metalloimmunoassay (CMIA) method is demonstrated. Three different pairings of antiepileptic medications from the groups carbamazepine, diphenylhydantoin, and phenobarbital (for each of which a mono-CMIA is already available) were assayed by double CMIA. The assay method employs as tracers metal–carbonyl complexes that give very strong signals in the range of 1850–2200 cm −1 in the infrared spectrum, permitting quantitative analysis by Fourier-transform infrared spectroscopy. The fact that the signals are individually assignable and of comparable intensity permits quantitative analysis of mixtures of two …
Removal of Escherichia coli from Saturated Sand Columns Supplemented with Hydrochar Produced from Maize
2014
Despite numerous studies on hydrochar use, its application in water treatment for pathogen removal remains unexplored. In this study, we evaluated the efficiency of hydrochar produced from crop residue of maize for water treatment by determining Escherchia coli breakthrough from sand columns supplemented with hydrochar. To enhance the adsorptive capacity, raw hydrochar was activated by 1 mol L⁻¹ KOH at room temperature. The experiments conducted in a 10-cm sand bed with 1.5% (w/w) activated and raw hydrochar supplements, not activated by KOH, showed 93 and 72% of E. coli removal efficiencies, respectively. Activation of KOH not only enhanced the E. coli removal but also increased the streng…