FT-Raman Spectroscopy Research Articles

Phenolic acids-induced aggregation of gluten proteins. Structural analysis of the gluten network using FT-Raman spectroscopy

The addition of polyphenols to wheat dough modifies the structure and mechanical properties of the gluten network. The aim of the study was to identify changes in the secondary and tertiary structure of gluten network induced by selected hydroxycinnamic and hydroxybenzoic acids with using FT-Raman spectroscopy. Phenolic acids were added to the model dough in concentrations of 0.05%, 0.1%, and 0.2% (w/w). Model flour consist of commercially available wheat starch and wheat gluten in proportions 80:15 (w/w). All phenolic acids caused similar alterations in the secondary structure of gluten proteins in terms of the creation of aggregated structures from α-helices, β-turns and hydrogen-bonded β-turns, although hydroxybenzoic acids induce more structural changes like pseudo-β-sheets. Furthermore, dough treatment with hydroxycinnamic derivatives results in faster dough breakdown than hydroxybenzoic acids. These results indicate that hydroxycinnamic acids have stronger interactions with gluten network in comparison to hydroxybenzoic acids. Further analysis showed that tryptophan residues were more buried in samples with phenolic acids containing methoxy groups. The interactions between phenolic acids and gluten proteins are complex, and they have been affected by the functional groups attached to the benzene ring as well as the concentration of phenolic acid and its size. Moreover, phenolic acids may primarily interact with glutenins.

Growth, spectral and quantum chemical investigation on hexamethylenetetramine 4-nitrophenol monohydrate single crystals for second harmonic generation and optical limiting applications

To grow single crystals of hexamethylenetetramine 4-nitrophenol monohydrate (HMTNP), the solvent evaporation method was used. The single crystal X-ray diffraction (SCXRD) method is used to confirm the crystal lattice parameters and space group. Powder X-ray diffraction, 1H, and 13C NMR, FTIR, and FT-Raman spectroscopy were employed to investigate the title crystal's crystalline nature, molecular arrangement, and presence of functional groups. The Hirshfeld surface study is aimed at investigating the intermolecular charge-transfer interactions that occur in HMTNP owing to the presence of OH···N, CH···O, and OH···O hydrogen bonds. UV-Visible and photoluminescence studies were used to determine the lower cut-off wavelength and emission peaks. Additionally, the title crystal's optical band gap energy has been estimated to be 3.17 nm. Dielectric and photoconductivity investigations of the single crystal revealed dielectric constant values and a negative photoconductivity response. The Second Harmonic Generation (SHG) efficiency of the powder crystal is 4.31 times that of a conventional KDP crystal. In Z-scan and optical limiting experiments, the self-defocusing nature and optical limiting behavior of HMTNP were demonstrated. Furthermore, DFT calculations at the B3LYP/6–311++G(d,p) level of theory were utilized to investigate the formed crystal's molecular structural geometry, molecular vibration, intermolecular charge transfer interactions and hyperpolarizability.

Synthesis and Characterization of Metallopolymer Networks Featuring Triple Shape-Memory Ability Based on Different Reversible Metal Complexes.

This study presents the synthesis and characterization of metallopolymer networks with a triple shape-memory ability. A covalently crosslinked polymer network featuring two different additional ligands in its side chains is synthesized via free radical polymerization (FRP). The subsequent addition of different metal salts leads to the selective formation of complexes with two different association constants (Ka), proven via isothermal titration calorimetry (ITC). Those two supramolecular crosslinks feature different activation temperatures and can act as two individual switching units enabling the fixation and recovery of two temporary shapes. The presented samples were investigated in a detailed fashion via differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and FT-Raman spectroscopy. Furthermore, thermo-mechanical analyses (TMA) revealed excellent dual and triple shape-memory abilities of the presented metallopolymer networks.

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 a polyphenol molecular size on the gluten proteins – polyphenols interactions studied with FT-Raman spectroscopy

Effect of a polyphenol molecular size on the gluten proteins – polyphenols interactions studied with FT-Raman spectroscopy

Architecture of a dinuclear Co(II) complex based on 3-amino-1,2,4-triazole-5-carboxylic acid: molecular structure, thermal behavior, optical properties, and DFT calculations

The dinuclear compound [Co2(Hatzc)2(H2O)6](NO3)2·4H2O containing the polytopic ligand Hatzc‒ = 3-amino-4H-1,2,4-triazole-5-carboxylate was synthesized and characterized. Single-crystal X-ray diffraction showed that two monoanionic N,O-chelating Hatzc‒ ligands bridge two Co(II) ions in a µ-N1,N2 fashion. Both Co(II) centers are further coordinated by three H2O ligands making up an octahedral coordination. A complex network of intra- and intermolecular O‒H···O and N‒H···O hydrogen bonding interactions characterize the structure. Hirshfeld surface analysis, ATR–FTIR, and FT-Raman spectroscopy in combination with density functional theory (DFT) calculation of vibrational modes confirm this multitude of H bonds. Thermogravimetric and differential thermal analysis experiments under an argon atmosphere in the temperature range of 25–900 °C showed thermal stability till about 100 °C and multi-step decomposition yielding Co2O3 at about 280 °C. The octahedral environment of Co(II) was confirmed by UV–vis absorption spectroscopy, which shows weak absorption bands at around 520 nm assignable to electronic d‒d transitions alongside with π‒π* transitions dominating the 250–350 nm range. Time-dependent DFT calculated excited states agree very well in terms of energy match with the observed transitions. The direct and indirect optical band gap values were determined using the Tauc plot method to 3.33 eV and 2.75 eV, respectively, indicating semiconducting properties.

The Influence of Water-Unextractable Arabinoxylan and Its Hydrolysates on the Aggregation and Structure of Gluten Proteins.

This study aimed to investigate the influence of water-unextractable arabinoxylan (WUAX) and its hydrolysates on the aggregation and structure of gluten proteins and reveal the underlying mechanism. In this work, the WUAX was treated with enzymatic hydrolysis and the changes of their molecular weights and structures were analyzed. Meanwhile, the conformation and aggregation of gluten were determined by reversed-phase HPLC, FT-Raman spectroscopy, and confocal laser scanning microscopy. The results showed that the extra WUAX could impair the formation of high Mw glutenin subunits, and the enzymatic hydrolysis arabinoxylan (EAX) could induce the aggregation of gluten subunits. And, the gluten microstructure was destroyed by WUAX and improved by EAX. Besides, the interactions of WUAX and EAX with gluten molecules were different. In summary, these results indicated that enzymatic hydrolysis changed the physicochemical properties of arabinoxylan and affected the interaction between arabinoxylan and gluten proteins.

Reliable and realistic models for lignin content determination in poplar wood based on FT-Raman spectroscopy

Studying lignin content is critical for analyzing the inherent constitution, performance, and application of lignocellulosic materials. However, the traditional methods (wet chemical methods) for the determination of lignin content have several limitations such as labor intensive, time-consuming preparations, and the use of toxic reagents. To address these shortcomings, based on 140 groups of poplar samples, a strategy of 1064 nm FT-Raman spectroscopy combined with several algorithms was proposed in our study. Before modeling, smoothing algorithm (Savitzky-Golay), baseline correction algorithm (adaptive iteratively reweighted penalized least squares), and deconvolution algorithm (Gaussian and Lorentzian) were applied to extract the Raman information. Also, several peaks including 1095, 1378, and 2895 cm−1 were selected as the candidates of internal standard peak for normalizing the lignin-related peaks. Subsequently, lignin content predictive models were established based on data extracted from FT-Raman spectra combined with regression algorithms, including principal components regression (PCR), partial least square regression (PLSR), ridge regression (RR), lasso regression (LR), and elastic net regressions (ENR). Consequently, credible models were obtained based on data normalized by peak of 2895 cm−1 combined with RR, LR, and ENR algorithms (Pearson’s R > 0.88, RMSE < 0.62, MAE < 0.46, and MAPE < 1.92%). Thus, the lignin quantitative models based on Raman spectroscopy developed here can be used to predict the lignin content in poplar clones accurately and efficiently.

Molecular structure determination, spectroscopic, quantum computational studies and molecular docking of 4-(E)-[2-(benzylamino)phenylimino) methyl-2]ethoxy phenol

A Schiff base compound 4-(E)-[2-(benzylamino)phenylimino)methyl-2]ethoxy phenol (4BPM2EP) was synthesized and spectroscopic characterization was performed using experimental methods such as FT-IR, FT-Raman and UV-Vis spectroscopy. Density functional theory (DFT/B3LYP/6-311++G(d,p)) computation was used to investigate the optimized molecular geometry, harmonic vibrational wavenumber, NMR chemical shifts, natural bond orbital (NBO) analysis, non-linear optical (NLO) properties, molecular electrostatic potential (MEP) map and Mulliken atomic charges of 4BPM2EP molecule. TD-DFT calculations have been carried out on the optimized geometry at gaseous phase, DMSO and ethanol to further understand the electronic transitions and solvents effect on the UV-Vis spectra of the compound. The assignments of vibrational modes were performed on the basis of total energy distribution (TED) using VEDA 4 program and were compared with experimental data. Molecular docking study was performed using Glide program to establish the information about the interactions between the topoisomerase DNA gyrase enzymes and the novel compound in order to explore the biological behaviour of the examined compound. The compound screened against four pathogens two gram positive, two gram negative and two fungal strains had shown good anti-bacterial and antifungal behaviour. Furthermore the compound was subjected to in-silico ADMET studies. Communicated by Ramaswamy H. Sarma

A comparative study of meat quality and vibrational spectroscopic properties of different chicken breeds

Chicken breed is one of the key factors that influence meat quality. The quality attributes of breast meat from commercial broiler (CB), Thai native chicken (NC, Leung Hang Khao), and the crossbred Korat chicken (KC) were investigated via synchrotron radiation-based Fourier transform infrared (SR-FTIR) microspectroscopy, Fourier transform Raman (FT-Raman) spectroscopy, and physicochemical analysis. The protein and carbonyl contents of KC and NC meats were higher than that of CB meat, but the lipid content was lower (P < 0.05). CB meat was characterized by high moisture, lightness (L*), and presence of taste-active nucleotides, namely, inosine 5′-monophosphate (IMP) and guanosine 5′-monophosphate (GMP). Moreover, NC meat had the highest insoluble collagen and inosine contents (P < 0.05). The predominant protein secondary structures of KC and NC meats were β-turns and random coils, whereas α-helices were mainly found in CB meat. Based on principal component analysis, the meat quality and spectra were clearly separated by breeds. The high moisture and lipid content of meat corresponded to O–H stretching (3,203 cm−1) and C–H stretching (2,854 cm−1) in the FT-Raman spectra, whereas PO2− stretching (1,240 cm−1), measured via SR-FTIR, was well correlated with the IMP content. In addition, the FT-Raman wavenumber of 934 cm−1, indicating C–C stretching, was correlated with high water-holding capacity (WHC) in KC meat. The quality of meat from slow- and fast-growing chickens significantly varies. Vibrational spectroscopy is a powerful technique that provides insightful molecular information correlated with various meat attributes.

Fruit spirits fingerprint pointed out through artificial intelligence and FT-Raman spectroscopy

The application of artificial intelligence, i.e. Machine Learning, represents a step forward in food metabolomics/authentication approaches. The present study demonstrates the applicability of the FT-Raman spectroscopy in association with Machine Learning algorithms, for trademark fingerprint assessment of fruit spirits. Thus, based on the best obtained model, a prediction ability of 96.2% was achieved. A good geographical origin prediction of investigated distillates was attained, despite that this classification was a very challenging one taking into account that the separation was made inside close Transylvanian areas. For botanical recognition, the obtained differentiation was quite modest suggesting that the differentiations which appear among the spirits prepared from various fruits are too subtle to be unequivocal detected through this proposed approach. In order to improve the prediction ability, different spectral ranges (Stokes and anti-Stokes) were considered and the best spectral interval for each classification model was identified and distinct Machine Learning algorithms were tested.

Vibrational spectra, force constants and quantum chemical calculations of μ-1,3-azide bridged triphenylphosphine complexes of copper(I) and silver(I)

The dimeric title compounds [(C6H5)3P]Cu2(N3)2 and [C6H5)3P]Ag2(N3)2 were synthesized and characterized by FT-Raman and IR spectroscopy. The two phases were not isotypic but possessed approximately the same molecular symmetry which was C2/2m. The assignment of the modes was supported by quantum chemical DFT calculations coupled with TED (Total Energy Distribution) analyses. The calculated (NN) force constants for the bridging --(NNN)-- groups were directly comparable (f(NN) = 11.75 (Cu) and 12.19 N cm−1(Ag)) and harmonized well with those of the free azide anion in the binary alkali azides. The (NN) bond orders were obtained based on the calculated force constants (Siebert Bond Order, SBO) and Density-dependent electrostatic and chemical (DDEC6) method yielding SBO = 1.92 (Cu) and 1.96 (Ag) and BO = 2.00 (Cu) and 2.03 (Ag), respectively, indicating the presence of double bonds. The results underlined that the (NN) force constants and bond orders in the bridging azide units were practically unaffected by the nature of the central metal atoms and that they could be regarded as quasi isolated anions similar to those in the binary azide compounds.

Reply to “Comment on ‘Understanding first-order Raman spectra of boron carbides across the homogeneity range’ ”

In response to Werheit's Comment, we first discuss the following three points: (i) Attribution of the Raman bands with the help of calculations based on the density functional perturbation theory (DFPT), (ii) similarity of the Raman spectrum of boron carbide to the Raman spectrum of $\ensuremath{\alpha}$ rhombohedral boron, and (iii) dependence of the experimental Raman spectrum on the frequency of the excitation laser. Central to the point at stake, we also present a Raman spectrum computed for the first time on a 405-atom unit-cell of boron carbide, where the simulation cell accounts for the substitutional disorder of the polar carbon atom in the six atomic positions that are equivalent in the trigonal symmetry. We thus obtain a theoretical spectrum whose agreement with experiment is unprecedented in boron carbide, all of the features being present, with however negligible intensities for the doublet at $270/320\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$. We argue that the doublet intensity seen in experiments is not purely vibrational---as computed at mechanical equilibrium---and that FT-Raman spectroscopy taken at $1.06\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{m}$ lacks the accuracy that is necessary to study vibrational modes of boron carbides.

Phytotoxic Effects of Selected Herbal Extracts on the Germination, Growth and Metabolism of Mustard and Oilseed Rape

The use of plants that have high allelopathic potential as natural herbicides in the form of aqueous extracts is gaining popularity in environmentally friendly agriculture. Usually, their effect on the germination and growth of weeds is investigated. However, less attention is paid to the effect of the allelopathic compounds from extracts on cultivated plants. Therefore, the aim of this study was to evaluate the impact of herbal extracts that have allelopathic properties on selected physiological and biochemical processes of two plants of great economic importance—white mustard (Sinapis alba L.) and oilseed rape (Brassica napus L. var. oleifera). The extracts were prepared from mountain arnica (Arnica montana L.), ribwort (Plantago lanceolata L.), hypericum (Hypericum perforatum L.), common milfoil (Achillea millefolium L.), sunflower (Helianthus annuus L.) and sage (Salvia officinalis L.). The germination of white mustard and oilseed rape was most inhibited by the extracts that were prepared from sage and sunflower. Additionally, in the germinating plants, the sunflower extracts increased the membrane permeability, which indicates membrane injuries. The metabolic changes in the plants were monitored using isothermal calorimetry and FT-Raman spectroscopy. The total heat production, which provided information about the metabolic activity of the white mustard and oilseed rape, was decreased the most by the sage extract but generally all of the tested extracts disturbed the shape of the heat emission curves compared to the water control. The impact of the allelopathic compounds that are present in the herbal extracts on the metabolism of the seedlings was clearly visible on the FT-Raman spectra—in the fatty acids and flavonoids range, confirmed using a cluster analysis. In conclusion, the herbal extracts from medicinal plants that have herbicidal activity could be used as a natural herbicide for weed control, but since they may also have negative impacts on cultivated plants, preliminary tests are advisable to find the extract from the species that has the least negative effect on a protected crop.

Effect of precursor dilution solvents on the growth of V2O5 thin films using spray pyrolysis

Using the ultrasonically nebulized spray pyrolysis of the aqueous combustion mixture (UNSPACM) technique, the effect of precursor dilution solvents on the growth of V2O5 thin films is reported. V2O5 thin films are grown by spraying an aqueous combustion mixture (ACM) onto glass substrates at 400°C. Methanol and ethanol are used to dilute the ACM. FESEM, XRD, and FT-Raman spectroscopic analysis are used to examine the surface microstructure, crystallographic information, and functional groups of the grown thin films respectively. The results show that thin films grown by diluting ACM with methanol produce the best results.

Experimental and theoretical spectroscopic properties of 2,3-Dimethoxybenzaldehyde using quantum chemical method

The interpretation of active functional groups have been characterized by FT-IR and FT-Raman spectroscopies with the help of potential energy distributions. Hartree-Fock (HF) calculations of the 2,3-Dimethoxybenzaldehyde (DMBA) carried out by 6-311++G(d,p) basis set. Hyperconjugative associations present in the particle were likewise evaluated utilizing normal bond orbital (NBO) examination. The condensed Fukui functions explored the sites available for nucleophilic and electrophilic attack in the form of local based descriptors.

Experimentally and theoretically via high quality density function theory modelling technique and nonlinear optical analyses of 2,6-Dimethoxy-4-hydroxybenzaldehyde

In this study, we reported the results of experimental and density of functional theory (DFT) of 2,6-Dimethoxy-4-hydroxybenzaldehyde (DMHB). The interpretation of active functional groups has been characterized by Fourier Transform-Infrared (FT-IR) and Fourier Transform-Raman (FT-Raman) spectroscopies with the help of potential energy distributions. DFT calculations of the DMHB compound were carried out by B3LYP/6–311 + G(d,p) method. In addition, FT-IR and FT-Raman spectral parameters that have been seen are produced from derivative structures and compared to experimental spectral frequencies. The practical application of DMHB is investigated by determining their electronic and NLO properties, which shows that both molecules have the potential for optoelectronic and photonic applications.

Spectroscopic and quantum chemical computation on molecular structure, AIM, ELF, RDG, NCI, and NLO activity of 4-VINYL benzoic acid: A DFT approach

Vibrational spectral analysis was carried out for 4-Vinyl Benzoic acid (4VBA) by using Fourier transform infrared (FT-IR) and FT-Raman spectroscopy in the range of 400–4000 and 50–3500 cm−1 respectively. The optimized geometrical parameters were computationally obtained at the DFT/B3LYP level of theory. The distribution of the vibrational bands was carried out with the help of normal coordinate analysis (NCA). The resulting harmonic wavenumbers were scaled by using NCA method. 13C and 1H NMR spectra were recorded and 13C and 1H nuclear magnetic resonance chemical shifts of the molecule were calculated using the gauge independent atomic orbital (GIAO) method. Topological analysis, such as Electron localization function (ELF), natural bond orbital analysis (NBO), reduced density gradient (RDG) and atoms in molecule (AIM) analysis, molecular electrostatic potential (MEP) have been used to evaluate the intermolecular interaction, especially the hydrogen bonds. UV-visible spectrum of the compound was recorded in the region 200–900 nm and the electronic properties and HOMO-LUMO energies were calculated by time dependent density functional theory approach.

Structure and absolute configuration of parodiolide, a new dimeric sesquiterpene lactone isolated from Mikania parodii Cabrera possessing an uncommon spiro connexion

A new dimeric sesquiterpene lactone named parodiolide was isolated from Mikania parodii Cabrera. Its structure and relative stereochemistry were established by HR-MS, 1H- and 13C NMR spectroscopy using 1D and 2D experiments in combination with the use of FT-IR, FT-Raman and UV-Visible spectroscopies. The combination of B3LYP/6-31G* calculations with experimental results revealed its structural and topological properties showing a rare spiro connection, and allowed to establish the absolute configuration of its ten chiral centers. The predicted solvation energy of parodiolide in methanol is -167.9 kJ/mol. Mapped MEP surfaces show nucleophilic sites on two lactone rings while on H atoms of CCH2 and C=CH groups, electrophilic sites are observed. NBO and AIM studies have shown a higher stability of parodiolide in methanol solution while its gap value in the same medium suggest reactivity comparable to other sesquiterpene lactones, such as cnicin and onopordopicrin. The atomic orbitals of the rings contribute to the increase of the gap value, decreasing their reactivity and potency in solution. Very good correlations were observed when the predicted infrared, Raman, NMR and ECD spectra were compared with the corresponding experimental ones. Complete assignments of the vibration normal modes and the main force constants are also reported for paradiolide in both media. Finally, the ECD spectrum in methanol solution confirms the absolute configuration of parodiolide.

Compounds extracted from solid fermentation of Pleurotus sajor‐caju for application as a natural antibacterial agent

Edible mushrooms have been the object of studies regarding their bioactive properties, acting mainly in the pharmaceutical and food areas. This study aimed at the production, extraction and purification of antibacterial compounds from Pleurotus sajor-caju. The identification of these compounds occurred by analysis via FT-Raman spectroscopy. Antibacterial extraction had a positive response, resulting in two compounds. The compound extracted at 25°C inhibited the development of Staphylococcus aureus by 52.7 ± 2.7 (%). The compound had a molecular size greater than 100 kDa and a possibly little branched structure. At a temperature of 60°C, the compound with the greatest antagonistic activity against Escherichia coli, reduced its development by 74.3 ± 1.8 (%). The compound was possibly a linear or slightly branched chain biomolecule and molecular weight between 50 and 100 kDa. According to the literature, it is estimated that the extracted compounds refer to β-glucan structures. Novelty impact statement The extract showed potential of inhibition above 50% for gram-positive and gram-negative microorganisms. The purification processes were efficient, reaching a 23.5-fold increase in bioactive capacity. It is estimated that different β-glucan structures were extracted.