Near-infrared FT-Raman Spectroscopy Research Articles

Comparison of a compatible and an incompatible pepper-tobamovirus interaction by biochemical and non-invasive techniques: Chlorophyll a fluorescence, isothermal calorimetry and FT-Raman spectroscopy

Leaves of a pepper cultivar harboring the L3 resistance gene were inoculated with Obuda pepper virus (ObPV), which led to the appearance of hypersensitive necrotic lesions approx. 72 h post-inoculation (hpi) (incompatible interaction), or with Pepper mild mottle virus (PMMoV) that caused no visible symptoms on the inoculated leaves (compatible interaction). ObPV inoculation of leaves resulted in ion leakage already 18 hpi, up-regulation of a pepper carotenoid cleavage dioxygenase (CCD) gene from 24 hpi, heat emission and declining chlorophyll a content from 48 hpi, and partial desiccation from 72 hpi. After the appearance of necrotic lesions a strong inhibition of photochemical energy conversion was observed, which led to photochemically inactive leaf areas 96 hpi. However, leaf tissues adjacent to these inactive areas showed elevated ΦPSII and Fv/Fm values proving the advantage of chlorophyll a imaging technique. PMMoV inoculation also led to a significant rise of ion leakage and heat emission, to the up-regulation of the pepper CCD gene as well as to decreased PSII efficiency, but these responses were much weaker than in the case of ObPV inoculation. Chlorophyll b and total carotenoid contents as measured by spectrophotometric methods were not significantly influenced by any virus inoculations when these pigment contents were calculated on leaf surface basis. On the other hand, near-infrared FT-Raman spectroscopy showed an increase of carotenoid content in ObPV-inoculated leaves suggesting that the two techniques detect different sets of compounds.

Rapid identification of black peanut seeds by confocal micro-Raman and near-infrared FT-Raman spectroscopy

Confocal micro-Raman spectroscopy and near-infrared (NIR) FT-Raman spectroscopy were used to analyse and identify cotyledons and the skins of black, white, red and ordinary pink peanut seeds.

The Application of NIR FT-Raman Spectroscopy to Monitor Starch Retrogradation and Crumb Firmness in Semolina Bread

In this study, the potential application of near-infrared (NIR) Fourier-transform (FT)-Raman spectroscopy to monitor starch retrogradation in stored bread crumb was investigated. Semolina-based bread was made and cut into slices, which were stored under controlled conditions in sealed plastic bags. The aging of the bread crumb was monitored by both NIR FT-Raman spectroscopy and a texture analysis over a period of 20 days. Two-dimensional correlation analysis in the spectral range of 390–975 cm−1 revealed characteristic differences among the spectra collected over time for bands that peaked at 480, 765, and 850 cm−1. The band at 480 cm−1 is studied here in detail. During the storage, the peak frequency of this band shifted towards lower wavenumbers, and its full width at half height decreased. Both of these parameters are highly correlated (R2 = 0.921 and R2 = 0.949, respectively) to crumb hardness measured by the texture analyzer.

Vibrational spectroscopy of extant and fossil microbes: Relevance for the astrobiological exploration of Mars

The vibrational spectra of an extant Archaea, Halobacterium salinarum, an extant micro-eukaryote resistant biopolymer isolated from Botrycoccus braunii, and an extinct (ca. 590–565 Ma) micro-eukaryote microfossil Tanarium conoideum, have been recorded using near-infrared FT Raman spectroscopy and FTIR spectroscopy. Raman biosignatures for the carotenoid pigment, bacterioruberin was obtained from the halophilic Archaea H. salinarum. Another pigment biosynthesized by halophilic Archaea, bacteriorhodopsin a retinal-protein complex was also investigated. The FTIR analysis of H. salinarum showed the presence of proteins and lipids, and the spectrum of isolated bacteriorhodopsin was different in that it contained retinal C–C stretching bands. FT Raman and FTIR analysis of the resistant biopolymer isolated from B. braunii indicated a composition of long straight chain polymethylenic macromolecule—termed algaenan. Moreover, these biopolymers can be preserved on geological timescales, hence the importance of generating a database of these materials for palaeobiology and astrobiology applications. The FT Raman and FTIR spectra acquired from T. conoideum contain intense aliphatic C–H stretching modes in the 2700–3000 cm −1 region. Both the FT-Raman and FTIR spectra are consistent with vibrational spectra obtained from algaenans isolated from extant chlorophytes, for example, B. braunii, or eustigmatophyte micro-algae.

Applications of near-infrared FT-Raman spectroscopy in metamict and annealed zircon: oxidation state of U ions

We report a near-infrared Fourier-transform (FT) Raman spectroscopic method to characterize the electronic transitions of U ions and the alpha-decay damage in natural zircon. The application is demonstrated by analyzing metamict and annealed zircons from Sri Lanka. The data from crystalline zircon reveal a relatively sharp spectral feature appearing near 2733 cm−1 in Stokes spectra with a laser excitation of 1064 nm. The feature is assigned as signals related to the previously reported U5+ absorption near 6668 cm−1. With increasing self-irradiation dose, the feature shows a systematic decrease in intensity, accompanied by a gradual development of a broad feature between 3000 and 3400 cm−1. On heating for 1 h, the U5+ feature shows an increase in intensity starting near ~700 K for partially metamict zircon, whereas for highly damaged zircon the first recovery of the feature takes place near 1000 K, accompanied by a decrease in the radiation-induced broad band. The changes observed in the present study reflect the variations of local environments of U ions in natural zircon during metamictization and thermal annealing.

Near-infrared FT-Raman spectroscopy as a rapid analytical tool for the determination of diltiazem hydrochloride in tablets

This study was performed to develop a fast and reliable analytical method for the quantitative determination of diltiazem hydrochloride in tablets. HPLC is currently the preferred method, but is time consuming due to extensive sample preparation. FT-Raman spectroscopy was used to quantitatively analyse diltiazem hydrochloride in commercially available tablets (Tildiem ®) and in experimental tablets prepared at lab-scale. The percentage of diltiazem hydrochloride in each tablet was determined by calculating—after vector normalisation—the total peak area of the spectral band between 1625 and 1560 cm −1. No spectral interference from tablet excipients was seen at this spectral band. After FT-Raman spectroscopy the same samples were analyzed based on the HPLC method described in the USP XXIV. The drug dosage per tablet obtained from the vibrational spectroscopy method correlated well with the results obtained using HPLC analysis for both the commercial tablets (HPLC: 63.57±0.13 mg; Raman: 63.28±0.26 mg ( n=50)) and the experimental tablets (HPLC: 181.02±0.25 mg; Raman: 181.22±0.35 mg ( n=50)). FT-Raman is a reliable alternative for the HPLC method to quantify the amount of diltiazem hydrochloride in tablets. The spectroscopic method is faster because it eliminates sample pre-treatment. Furthermore the FT-Raman method has an additional advantage of not requiring solvents.

Detection of Pinosylvins in Solid Wood of Scots Pine Using Fourier Transform Raman and Infrared Spectroscopy

Diffuse reflectance Fourier transform infrared (DRIFT) and near infrared (NIR) FT-Raman spectroscopy were used to detect pinosylvins in the wood of Pinus sylvestris L. trees. NIR FT-Raman spectroscopy offered the possibility of revealing pinosylvins simply by visual inspection of Raman spectra whereas DRIFT spectra needed a more complicated evaluation. Pinosylvin and resin acids from Scots pine were examined as to the possibility of their being the cause of observed spectral differences between sapwood and heartwood. Since pinosylvins are important compounds for the decay resistance of Scots pine wood, the detection of pinosylvins with Raman spectroscopy might be used to assess durability of wood products.

Fourier transform Raman spectroscopic studies of a novel wood pulp bleaching system

The use of near-infrared (NIR) Fourier transform (FT) Raman spectroscopy for the study of lignocellulosic materials is discussed. An application utilizing NIR FT-Raman spectroscopy to study a novel chlorine-free process for the bleaching of wood pulps is presented in detail. The new process, still under development, entails the oxidation of residual lignin in wood pulps by vanadium-substituted polyoxometalates, and reoxidation of the reduced polyoxometalates by chlorine-free oxidants such as air, dioxygen, peroxides or ozone. Results from FT-Raman measurements of polyoxometalate-treated pulps are compared with those from chemical, spectroscopic and optical techniques commonly used in the pulp and paper industry.

Fourier transform Raman spectroscopy of the bacteriorhodopsin mutant Tyr-185 .fwdarw. Phe: Formation of a stable O-like species during light adaptation and detection of its transient N-like photoproduct

Near-infrared FT-Raman spectroscopy can be used to measure the vibrations of the bacteriorhodopsin (bR) chromophore without the disadvantage of conventional visible resonance Raman spectroscopy, where the visible excitation drives the bR photoreactions. We utilized this technique to investigate the light-dark adaptation of bacteriorhodopsin and the mutant Tyr-185-->Phe (Y185F) at room temperature in solution. Compared to wild-type bR, both the FT-Raman and resonance Raman spectra of the light-adapted Y185F displayed new features characteristic of the vibrations of the O intermediate. Light adaptation of Y185F was found to involve a 13-cis, C=N syn-->all-trans isomerization of the retinal chromophore which produces a species similar to bR570 and a second O-like species. Dark adaptation, which was much slower in Y185F compared to wild-type bR, involved a parallel decay of the bR570 and O-like species and resulted in a decreased all-trans:13-cis ratio compared to wild type. Further evidence for the existence of an O-like species in Y185F comes from pump-probe Raman difference spectroscopy, where a red pump beam is found to produce a species very similar to the N intermediate in the photocycle. This species is shown by stroboscopic Raman measurements to exist transiently even at high pH. We postulate that when the Y185F chromophore has an all-trans structure the effective pKa of Asp-85 and Asp-212 is elevated in Y185F due to the disruption of the Asp-212/Tyr-185 hydrogen bond, thereby accounting for the increased protonation of these residues in the O-like species.

Potential of Near-Infrared Fourier Transform Raman Spectroscopy in Food Analysis

The 1064-nm excited Fourier transform (FT) Raman spectra have been measured in situ for various foods in order to investigate the potential of near-infrared (NIR) FT-Raman spectroscopy in food analysis. It is demonstrated here that NIR FT-Raman spectroscopy is a very powerful technique for (1) detecting selectively the trace components in foodstuffs, (2) estimating the degree of unsaturation of fatty acids included in foods, (3) investigating the structure of food components, and (4) monitoring changes in the quality of foods. Carotenoids included in foods give two intense bands near 1530 and 1160 cm−1 via the pre-resonance Raman effect in the NIR FT-Raman spectra, and therefore, the NIR FT-Raman technique can be employed to detect them nondestructively. Foods consisting largely of lipids such as oils, tallow, and butter show bands near 1658 and 1443 cm−1 due to C=C stretching modes of cis unsaturated fatty acid parts and CH2 scissoring modes of saturated fatty acid parts, respectively. It has been found that there is a linear correlation for various kinds of lipid-containing foods between the iodine value (number) and the intensity ratio of two bands at 1658 and 1443 cm−1 ( I1658/ I1443), indicating that the ratio can be used as a practical indicator for estimating the unsaturation level of a wide range of lipid-containing foods. A comparison of the Raman spectra of raw and boiled egg white shows that the amide I band shifts from 1666 to 1677 cm−1 and the intensity of the amide III band at 1275 cm−1 decreases upon boiling. These observations indicate that most α-helix structure changes into unordered structure in the proteins constituting egg white upon boiling. The NIR FT-Raman spectrum of old-leaf (about one year old) Japanese tea has been compared with that of its new leaf. The intensity ratio of two bands at 1529 and 1446 cm−1 ( I1529/ I1446), assignable to carotenoid and proteins, respectively, is considerably smaller in the former than in the latter, indicating that the ratio is useful for monitoring the changes in the quality of Japanese tea.

Biological applications of near- IR fourier-transform Raman microspectroscopy

Recently-developed near-infrared Fourier transform (FT)-Raman spectroscopy has received keen interest of researchers in bio-Raman field because near-infrared excitation can avoid mostly fluorescence and photodecomposition, which have been two major drawbacks of Raman spectroscopy in its biological and medical applications. Introduction of FT-Raman microspectroscopy makes near-infrared FT-Raman spectroscopy more useful for studying biomedical materials. The purpose of the present paper is to demonstrate the potential of near-infrared FT-Raman microspectroscopy in nondestructive structural analysis of biological systems. Photosynthetic bacteria is taken up here as an example.The FT-Raman spectra of the photosynthetic bacteria were measured with a JEOL JRS-FT6500N FT-Raman spectrometer equipped with an optical microscopy. Excitation wavelength at 1064-nm was provided by a CW Nd:YAG laser (CVI YAGMAX c-92), and the laser power at the sample position was typically 150 mW. All the data were collected at a spectral resolution of 8 cm-1 and spatial resolution of 8 μm.