Search results for " Fourier"

Fractional Fourier Transforms and Geometrical Optics

2010

Assessment of temperature effects on beta-aggregation of native and glycated albumin by FTIR spectroscopy and PAGE: relations between structural chan…

2007

Abstract Structural modifications of bovine serum albumin (BSA) induced by heating, and the involvement of glycation of albumin in such processing were studied by using Fourier transform infrared spectroscopy (FTIR) and polyacrylamide gel electrophoresis (PAGE). For native BSA, heating treatments gave rise to β structures which were amplified to the detriment of α-helix form, and which were associated with increased aggregation. A very high correlation was obtained between FTIR Amide I band evolution and aggregation rate parameters, showing the contribution of β-form in aggregates formation. We further assessed the effect of glycation on protein sensibility to heating treatments. A reductio…

Thermal aggregation of glycated bovine serum albumin

2010

International audience; Aggregation and glycation processes in proteins have a particular interest in medicine fields and in food technology. Serum albumins are model proteins which are able to self-assembly in aggregates and also sensitive to a non-enzymatic glycation in cases of diabetes. In this work, we firstly reported a study on the glycation and oxidation effects on the structure of bovine serum albumin (BSA). The experimental approach is based on the study of conformational changes of BSA at secondary and tertiary structures by FTIR absorption and fluorescence spectroscopy, respectively. Secondly, we analysed the thermal aggregation process on BSA glycated with different glucose con…

Relevance of Interactions between Starch-based Coatings and Plum Fruit Surfaces: A Physical-Chemical Analysis

2019

In order to extend the shelf life of the fruit, improve appearance, and to keep all nutrition properties of the plum from diminishing, edible coatings comprised of wheat starch and wheat starch&ndash

Keggin heteropolyacid supported on TiO2 used in gas-solid (photo)catalytic propene hydration and in liquid-solid photocatalytic glycerol dehydration

2017

Abstract (Photo)catalytic propene hydration to 2-propanol and glycerol dehydration to acrolein were carried out by using Keggin heteropolyacids (HPAs) supported on TiO 2 . Binary materials have been prepared by impregnation of H 3 PW 12 O 40 , H 3 PMo 12 O 40 and H 4 SiW 12 O 40 , on TiO 2 Evonik P25. Moreover, a binary material consisting of H 4 SiW 12 O 40 and TiO 2 was prepared via a hydrothermal treatment and tested for the same reactions. All the materials were characterized by X-ray diffraction (XRD), scanning electron microscopy observations (SEM) coupled with energy dispersive X-ray (EDX) measurements, diffuse reflectance spectroscopy (DRS), Raman spectroscopy and Fourier transform …

New biodegradable hydrogels based on a photocrosslinkable modified polyaspartamide: synthesis and characterization

1999

Abstract α,β-Poly( N -2-hydroxyethyl)- dl -aspartamide (PHEA), a synthetic water-soluble biocompatible polymer, was derivatized with glycidyl methacrylate (GMA), in order to introduce in its structure chemical residues having double bonds and ester groups. The obtained copolymer (PHG) contained 29 mol% of GMA residues. PHG aqueous solutions at various concentrations ranging from 30 to 70 mg/ml were exposed to a source of UV rays at λ 254 nm in the presence or in the absence of N , N ′-methylenebisacrylamide (BIS); the formation of compact gel phases was observed beginning from 50 mg/ml. The obtained networks were characterized by FT-IR spectrophotometry and swelling measurements which evide…

New biodegradable hydrogels based on an acryloylated polyaspartamide cross-linked by gamma irradiation

1999

Alpha, beta-poly(N-2-hydroxyethyl)-DL-aspartamide (PHEA), a synthetic biocompatible macromolecule, was functionalized with glycidyl methacrylate (GMA) in order to introduce in its side chains residues having double bonds and ester groups. The copolymer (PHG), obtained from PHEA and GMA, had a degree of derivatization of 29 mol%. PHG aqueous solutions are cross-linked by gamma radiation at 0 degrees C either in the presence or absence of N,N'-methylenebisacrylamide (BIS) giving rise to new hydrogel systems. In both cases gelation occurs at quite low doses (0.26 and 0.4 kGy, respectively). The obtained networks were characterized by FT-IR spectrophotometry which confirmed that the cross-linki…

Biodegradable hydrogels obtained by photocrosslinking of dextran and polyaspartamide derivatives

2003

The functionalization of dextran with glycidyl methacrylate (GMA) leads to the formation of a derivative that generates hydrogels for irradiation at 365nm. The effects of various polymer concentrations and irradiation times on the yield and the properties of the obtained hydrogels are reported. The networks have been characterized by FT-IR spectra, dimensional analysis and swelling measurements carried out at different pH values. In vitro studies suggest that all samples undergo a partial chemical hydrolysis, whereas the incubation with dextranases causes a total degradation whose rate depends on the degree of crosslinking. In addition, aqueous solutions of functionalized dextran have been …

Interaction of metal ions with N-glycosylamines: isolation and characterization of the products of 4,6-O-benzylidene-N-(o-carboxyphenyl)-β-D-glucopyr…

2001

Metal-ion complexes of Li+, Na+, K+, Mg2+, Ca2+, Ba2+, Pb2+, Cd2+, Hg2+ with 4,6–O–benzylidene–N–(o–carboxyphenyl)–β–D–glucopyranosylamine were synthesized and isolated as solid products and characterized by analytical means as well as by spectral techniques, such as, 1H and 13C NMR, FTIR, absorption, FAB mass spectrometry, optical rotation and CD. While the alkali metal ions formed ML type of complexes, the other metal ions formed ML2 type complexes. Molecular weights of the complexes of Li+, Na+ and K+ were established based on the molecular-ion peaks in the FAB mass spectra. The saccharide portion remians in the β-anomeric form even after the complexation. The spectral data, as well as t…

Periodic Discrete Splines

2014

Periodic discrete splines with different periods and spans were introduced in Sect. 3.4. In this chapter, we discuss families of periodic discrete splines, whose periods and spans are powers of 2. As in the polynomial splines case, the Zak transform is extensively employed. It results in the Discrete Spline Harmonic Analysis (DSHA). Utilization of the Fast Fourier transform (FFT) enables us to implement all the computations in a fast explicit way.