Aleksandra Wesełucha-Birczyńska

FT-IR and FT-Raman study of hydrothermally degradated cellulose

Abstract Deterioration of books and archive materials is due to degradation of cellulose that is caused by many factors such as acidic hydrolysis, oxidative agents, light, air pollution or presence of microorganisms. Recently, FT-IR and FT-Raman spectroscopy have been used for the characterization of cellulose and its degradation products. In this work, we present vibrational spectra obtained with different sampling techniques of pure cellulose from softwood and cotton that has been hydrothermally treated for maximum 21 days in extreme humid atmosphere (100% humidity, 100°C). We show that the obtained results strictly depend upon spectroscopic techniques used in measurements. We also present and discuss changes in vibrational spectra pointing out a role that is played by water molecules in this accelerated aging process of paper.

Application of Fourier-transform infrared and Raman spectroscopy to study degradation of the wool fiber keratin

Abstract Wool fibers and products made from them accompany a man almost from the dawn of history. Wool is still the most popular natural material and it is irreplaceable for ecological reasons. However, environmental pollution makes irreversible changes in the structure of wool fibers. Consequently, natural resources of quality precious materials decrease. This situation induces actions which lead to the regeneration of wool fibers. In laboratory conditions wool fiber keratin was exposed to the hydrolytic degradation process in alkaline environment and then the attempt of interruption of this process in the presence of siliceous compounds was made. The changes in the structure of wool fiber keratin were studied by means of Fourier-transform Infrared and Raman Spectroscopy.

Thermal effects on the structure of cereal starches. EPR and Raman spectroscopy studies.

The mechanism of thermal radical generation has been studied in cereal starches containing different amylose contents. Samples of four corn starches and one of wheat has been investigated using electron paramagnetic resonance and Raman spectroscopies. It has been found, that the content of amylose influences the character of thermally created radical species, but in opposite to potato starch, does not affect their amount. During storage of thermally treated starches the evolution of the EPR spectra has been observed. Raman spectra reveal the smaller changes in cereal starches structure occurring upon high temperature than those found for potato starch.

The mechanism of thermal activated radical formation in potato starch studied by electron paramagnetic resonance and Raman spectroscopies

Degradation of starch and the constituent fractions: amylopectin and amylose during thermal treatment in the range 423-503 K was investigated by electron paramagnetic resonance (EPR) and Raman spectroscopy. Degradation process was accompanied by the generation of carbon-centered stable radicals. EPR provided data on the nature and structure of radicals and on their evolution upon thermal treatment, whereas Raman spectroscopy allowed monitoring the changes of bonds in polysaccharides. It was found that amylose was the most susceptible toward high temperatures and the process of radical generation started at lower temperature than in amylopectin and starch, which were more resistant to thermal degradation.

Evolution of the surface species of the V2O5–WO3 catalysts

Abstract Vanadia-related species formed as a result of vanadium segregation at the surface of V–W oxide bronze crystallites were investigated. The structures of these species and their transformations induced by oxygen removal and oxygen adsorption were monitored using photoelectron spectroscopy and the FT Raman technique. Assignments of the MeO vibrational bands, based on the results of DFT calculations for model clusters, have been proposed. Two kinds of surface species are dominant depending on the tungsten content: V 4+ –O–W 6+ at low tungsten content and V 5+ –O–W 5+ at higher tungsten concentration.

The influence of the starch component on thermal radical generation in flours.

Transition metal ions and radicals in flours of various botanical origins with different content of starch have been studied by EPR before and after thermal treatment. The amounts of metal ions, have been determined by ICP OES. Simulations of EPR spectra have revealed the presence of several types of radicals (carbon-centred, tyrosyl and semiquinone) localized in starch and protein fractions of flours. Thermal treatment of flours significantly increased the amount of radicals with a simultaneous decrease of the signal intensity of transition metal ions. The proposed mechanism of thermal generation of stable organic radicals was associated with the redox processes involving transition metal ions, which facilitated the formation of radicals. The dependence between the way starch is treated and the mechanism of radical formation was also shown.

Assessing secondary structure of a dyed wool fibre by means of FTIR and FTR spectroscopies

Abstract The paper describes changes in the structure of a wool fibre dyed with model azo dyes. These were direct dyes, non-genotoxic derivatives of carcinogenic benzidine, synthesized specially for the purpose of the experiment. The non-mutagenic benzidine derivatives were: 2,2′-dimethyl-5,5′-dipropoxybenzidine and 5,5′-dipropoxybenzidine. Using FTIR, changes in secondary structure of fibres were assessed in three measuring ranges: 3600–3000, 1700–1400 and 1000–1300 cm −1 . The dyes were found to distinctively affect wave-number shifts of amide A, amide I bands and in the fingerprint area around 1050 cm −1 . It seems that these three areas are related to the sites in which dyes bind with wool fibre keratin. In FTR spectra, the focus was on assessing the changes of peptide bond configuration in the area of amide I, disulfide area of cystine and the area of the interaction between dyes and wool fibre keratin, i.e. 1250–1600 cm −1 . For analysis, three kinds of materials were selected: (1) raw wool fibres, (2) fibres subjected to deuteration and treated with formic acid, (3) wool fabric. Each of them was dyed with the model azo dyes. The results obtained by both spectroscopies allow for identifying the functional groups responsible for the binding of dyes with keratin fibre.

Interaction of selected divalent metal ions with human ataxin-3 Q36.

The mode of interaction of ataxin-3 Q36 (AT-3 Q36) with selected endogenous and exogenous metal ions, namely, Zn2+, Cu2+, Ni2+, and Cd2+, was examined. Metal-ion-induced structural changes of the protein were monitored by fluorescence as well as Fourier transform Raman spectroscopy. We found that the cations tested lead to a decrease in α-helical content and a concurrent increase in β-sheet as well as undefined (β-turn and random-coil) structures. The most evident effect was observed for copper and nickel cations. After titration with these cations, the AT3 Q36 secondary structure content (27% α-helices in the presence of either ion, 31 and 27% β-sheets for Cu2+ and Ni2+, respectively) was similar to that observed for the aggregated form of the protein (27% α-helices, 36% β-sheets). Using the 1-anilinonaphthalene-8-sulfonate hydrophobic fluorescence probe, we showed that the presence of the metal ions tested led to the formation of solvent-exposed hydrophobic patches of AT-3 Q36, and that such an effect decreased with increasing ionic radius.

Structural studies of V2O5–WO3 and WO3–V2O5 solid solutions

Powder X-ray diffraction, Fourier transform Raman spectroscopy, solid-state NMR and X-ray photoelectron spectroscopy were used to determine the composition and structure of a mixed oxide containing 10 mol% V2O5 and 90 mol% WO3. The parent sample consists of hybrid crystallites of a tungsta-bronze isostructural with tetragonal WO3 but containing atomic vanadium in the bulk of the crystals and V(III) in the surface region, and of small crystals of strongly reduced vanadia-like surface species (V2O5–x with x=0.42). Further thermal treatment causes progressive surface segregation of vanadium from the V2O5–WO3 solid solution, accompanied by the formation of a WO3–V2O5 solid solution and partial tetragonal–monoclinic structural transformation of the bronze.

The application of Fourier-transform infrared (FTIR) and Raman spectroscopy (FTR) to the evaluation of structural changes in wool fibre keratin after deuterium exchange and modification by the orthosilicic acid

Abstract An injury of hair macrostructure and substantial alkalinity of the water–lipid shield medium on wool fibre surface is conducive to a transition of heavy metal elements into ion forms. It also helps SiO 2 in a transition into a colloidal form of orthosilicic acid and its penetration in this form of the wool fibre structure. Consequently, it leads to the biomineralization of the wool fibre [J. Mol. Struct. 511–512 (1999) 307; J. Mol. Struct. 511–512 (2000) 397]. Changes taking place in the process of biomineralization, mainly in the amorphous region, may be responsible for the effectiveness of the technological processes and the properties of ready wool products [3] . Wool fibres obtained from Polish Merino sheep were treated with solution of orthosilicic acid (H 4 SiO 4 · n H 2 O) in experimental conditions during which fibres first underwent extraction with methylene chloride and them with asolution of orthosilicic acid in alkaline medium. Studies of deuterium exchange in the wool fibre keratin were applied to study changes in the structure of wool fibre keratin in the process of orthosilicic acid treatment. The changes in the structure of wool fibre were studied by means of infrared spectroscopy (FTIR) and Raman spectroscopy (FTR).