Application Of FT-Raman Spectroscopy Research Articles

Interactions of gliadins with flavonoids and their glycosides studied with application of FT-Raman spectroscopy

FT-Raman spectroscopy was applied to study interactions between wheat gliadins and three flavonoids and their glycosides. Complexes gliadins-flavonoids/glycosides were extracted from the model wheat dough. As flavonoids were used quercetin, naringenin, hesperetin and their glycosides rutin, naringin, hesperidin in the amount of 0.05%, 0.1% and 0.2%. The analysis of the FT-Raman spectra showed that the tested compounds caused changes in the secondary and tertiary structure of gliadins. In the case of gliadins, these changes concerned mainly α-helices. Quercetin induced a different type of structural changes compared to naringenin and hesperetin, which was probably due to the presence of a double bond on the C ring and an additional OH group on the B ring in the structure of this molecule. On the other hand, the interactions of glycosides with gliadins were affected by the place of attachment of the sugar part in the structure of the glycoside. Flavonoids/glycosides significantly increased the content of disulfide bridges in the g-g-g conformation. Changes in the amino acid microenvironment (tyrosine and tryptophan) indicate the formation of a more ordered structure in gliadins.

Effect of chemical structure of selected phenolic acids on the structure of gluten proteins

Effect of overmixing process and structure of selected phenolic acids belonging to hydroxycinnamic and hydroxybenzoic group on the structure of gluten network were analysed with application of FT-Raman Spectroscopy. Modification of gluten by acids resulted in formation of aggregates and unordered structures at the expense of protein stabilizing structures (e.g. β-sheets or β-turns). Supplementation with most of the acids caused reduction in the amount of disulphide bonds in the most stable conformation (g-g-g). Changes in the molecular organization of gluten proteins depended on the chemical structure of particular acids. The presence of bands assigned to aggregates was connected with the number of OH groups present at the aromatic ring of the acids. Acids belonging to hydroxycinnamic group did not incorporate or incorporate only partially into gluten network by formation of covalent or hydrogen bonds. Spectrophotometric analysis showed that hydroxycinnamic acids can interact stronger with gluten proteins compared to hydroxybenzoic acids.

Effect of cinnamic acid and its derivatives on structure of gluten proteins – A study on model dough with application of FT-Raman spectroscopy

Fourier transform Raman spectroscopy was applied to study interactions between gluten proteins and five phenolic acids during mixing of the model dough. Phenolic acids: cinnamic, p-coumaric, caffeic, ferulic and chlorogenic acids were chosen and added in the amount of 0.05%, 0.1% and 0.2%. These compounds differ in the type of functional groups present at the phenolic aromatic ring, and hence antioxidant activity. Farinographic results show a change in the dough behaviour in the presence of phenolic acids which can be regarded as a dough breakdown. This phenomenon occurs the fastest for caffeic acid, and the slowest for p-coumaric acid that are characterized by the highest and lowest antioxidant activity, respectively. The structural changes observed in gluten proteins also depend on the antioxidant activity of phenolic acids. The largest changes were observed in conformation of disulphide bridges, content of free SH groups and tryptophan environment as a result of caffeic and chlorogenic acids addition. The present results indicate that the studied phenolic acids may incorporate into gluten network or may be closed in hydrophobic pockets without formation of any chemical bonds.

Effect of dietary fibre polysaccharides on structure and thermal properties of gluten proteins – A study on gluten dough with application of FT-Raman spectroscopy, TGA and DSC

The effect of four dietary fibre polysaccharides (microcrystalline cellulose (MCC), inulin (IN), apple pectin (AP) and citrus pectin (CP)) on structure and thermal properties of gluten proteins in the gluten dough was studied with application of FT-Raman spectroscopy, thermogravimetry (TGA) and differential scanning calorimetry (DSC). The commercially available wheat gluten was mixed with the polysaccharides in five concentrations: 3%, 6%, 9%, 12% and 18%. The obtained results showed that MCC, IN and small amount of pectin (3% and 6%) induced similar changes in the secondary structure of gluten proteins concerning formation of antiparallel-β-sheets connected by intermolecular hydrogen bonds from α-helices and β-sheets. Higher contents of pectin (9–18%) led to formation of aggregates and β-like aggregates. The observed changes in the secondary structure, conformation of disulphide bridges and environment of tyrosine and tryptophan of gluten proteins indicated partial dehydration of gluten network as a result of a competitive water binding by polysaccharides molecules (especially MCC and IN) during the dough mixing. TGA results also confirmed this statement. However, slightly different results were obtained for pectins. They not only competed for water with gluten proteins but also interacted with them since a thermogravimetric peak characteristic for pectin was observed in the derivative TGA profiles of gluten – pectin mixtures.

Application of FT-Raman Spectroscopy and Chemometric Analysis for Determination of Adulteration in Milk Powder

In this work, FT-Raman spectroscopy is explored as a rapid technique for the assessment of the milk powder quality. Based on information provided by Raman spectra of samples adulterated with starch and whey, a quantitative method is developed to identify the fraud, using Partial Least Squares regression (PLS). In regression models using PLS the results are satisfactory, and such models can be used to identify and quantify samples presenting whey and starch in milk powder at concentrations of 2.32% and 1.64% (w/w), respectively. In the whey determination, the obtained values in the PLS model of the new samples are compared with those obtained by the spectrophotometric method of acid ninhydrin. This result shows that there is no significant difference with the 95% level of confidence between the values provided by the PLS regression method and the acid ninhydrin. The present work shows Raman spectroscopy as an analytical tool which can be used in quality control of milk powder, even in fraud processes, and the calculated figures of merit such as sensitivity, accuracy, limit of detection and limit of quantification clearly demonstrate this potential use. Although the multivariate models developed are not strictly quantitative, especially for low concentrations, they can be used as screening methods for routine analysis, as showed by this work.

The effect of pressure on the bacteriochlorophyll a binding sites of the core antenna complex from Rhodospirillum rubrum.

In this paper we examine the effect of pressure on the absorption spectrum and binding site of the core antenna complex from the photosynthetic bacterium Rhodospirillum rubrum. Absorption spectra and Raman spectra in preresonance with the Qy transition of the bacteriochlorophyll a were studied at pressures up to 625 MPa. In agreement with previous work we observe a pressure-induced red shift and broadening of the absorption spectrum. We show that at these pressures the pigments within the protein matrix at room temperature experience little if any distortion, and the hydrogen-bonding network involving the C2 and C9 carbonyl groups of the pigment molecules are undisturbed. Having shown the lack of sensitivity to pressure of the binding site interactions, which are known to modulate the absorption spectrum, we feel that it is relatively safe to attribute the pressure-induced red shift broadly to solvatochromic effects and, in particular, to the modulation of the pigment-pigment interactions by the pressure. This paper represents the first vibrational study of photosynthetic complexes at high pressure and the first application of FT Raman spectroscopy to biological molecules at high pressure.

Lattice vibrations of montmorillonite: an FT Raman and X-ray diffraction study

The lattice vibrations of a series of dioctahedral montmorillonitic clay minerals were studied using FT Raman spectroscopy. The lattice vibrations are assigned in terms of the molecular vibrations of (a) the distorted octahedron MO 6 with symmetry S 6 in the region 50–200 cm −1, (b) the OHO isosceles triangle of C 2v symmetry in the 200 to 270 cm −1 and (c) distorted SiO 4 tetrahedra of symmetry C 3v in the region 300 to 1200 cm −1. The application of FT Raman spectroscopy to the analysis of montmorillonitic clay structure is elucidated. A series of montmorillonites with different weathering profiles from the Cressfield deposit in Australia were analysed by both FT Raman and X-ray diffraction. The FT Raman spectra of the Cressfield bentonites are shown to be a function of clay crystallinity. X-ray diffraction identified the changes in the montmorillonitic lattice as weathering occurs. The variation in the 001 d spacing changed from 17.53 to 17.36 Å and the CDS value increased from 126 to 148 Å, indicating an increase in both the order and crystallinity of the montmorillonite on ageing. FT Raman spectroscopy identified changes in the lattice vibrational modes as this weathering is taking place.

Fourier transform Raman spectroscopy of novel organic systems. The analysis of allenylketenimine—tetracyanoethylene Diels—Alder reaction products

Abstract The Diels—Alder reaction products of a series of allenylketenimines with tetracyanoethylene (TCNE) have been studied by Fourier transform (FT) Raman spectroscopy. Several characteristic vibrational features of the adducts are discussed. The application of FT-Raman spectroscopy to the analysis of the adducts is evaluated.

Fourier transform Raman spectroscopy: Its value in the study of polymers

AbstractThe advantages of FT Raman spectroscopy, using a near‐infrared excitation source, are discussed. The details of the instrumentation are described and the many applications of FT Raman spectroscopy in polymer science are surveyed.

Fourier transform Raman spectroscopy of superconducting YBa2Cu3O7-δ films on strontium titanate and magnesium oxide substrates

Thin sputtered films of the high-Tc material YBa2Cu3O7-Δ were investigated using 180° back-scattering geometry with Fourier transform (FT) Raman spectroscopy. It is established that the main bands in the spectra of a YBa2Cu3O7-Δ film on strontium titanate substrate exhibit similarity with those obtained for oriented untwinned crystallites of the superconductor having their c-axis perpendicular to the surface of the substrate. No degradation or excessive heating of the film was observed with 1.064 μm excitation for low laser powers. The film on a magnesium oxide substrate gives unique evidence of the isolated strong, featureless, almost flat continuum, producing a broad maximum near the region of the antiphase axial bending O(2)Cu(2)O(3) motions of planar oxygens at very low excitation energy. This appears to be the first application of FT-Raman spectroscopy using near-infrared excitation (1.064 μm) to the field of high-temperature superconducting films and their detailed characterization.

The application of fourier transform raman spectroscopy to the study of paint systems

Abstract This paper describes the application of FT Raman spectroscopy to three fields of analytical interest in the coatings industry: (1) an emulsion polymerization is monitored; (2) it is used, in conjunction with FTIR, to characterize an alkyd resin, and to follow its curing reactions; (3) it is used, along with ATR-FTIR, to evaluate painted panels which have been subjected to a prolonged weathering cycle. Points of interest to the analyst are noted, and future developments briefly discussed.

Applications of Fourier Transform Raman spectroscopy in the synthetic polymer field

Abstract The application of FT Raman spectroscopy in the study of a wide range of polymer systems is discussed. The following have been included to give the reader an insight into the variety of areas which can successfully be studied using this important technique: the problem of crystallinity; nylons; poly(aryl ether ketone) and poly(aryl ether ether ketone); poly(aryl ether ether sulphone) and poly(aryl ether sulphone); epoxy resin curing; copolymers; copolymers of tetrafluoroethylene and hexafluoropropylene; polythioethers; and gels.