In this paper, it is demonstrated how Raman spectroscopy can be used to detect different carotenoids as possible biomarkers in various groups of microorganisms. The question which arose from previous ...studies concerns the level of unambiguity of discriminating carotenoids using common Raman microspectrometers. A series of laboratory-grown microorganisms of different taxonomic affiliation was investigated, such as halophilic heterotrophic bacteria, cyanobacteria, the anoxygenic phototrophs, the non-halophilic heterotrophs as well as eukaryotes (Ochrophyta, Rhodophyta and Chlorophyta). The data presented show that Raman spectroscopy is a suitable tool to assess the presence of carotenoids of these organisms in cultures. Comparison is made with the high-performance liquid chromatography approach of analysing pigments in extracts. Direct measurements on cultures provide fast and reliable identification of the pigments. Some of the carotenoids studied are proposed as tracers for halophiles, in contrast with others which can be considered as biomarkers of other genera. The limits of application of Raman spectroscopy are discussed for a few cases where the current Raman spectroscopic approach does not allow discriminating structurally very similar carotenoids. The database reported can be used for applications in geobiology and exobiology for the detection of pigment signals in natural settings.
Raman spectroscopy is being adopted as a nondestructive instrumentation for the robotic exploration of Mars to search for traces of life in the geological record. Here, miniaturized Raman ...spectrometers of two different types equipped with 532 and 785 nm lasers for excitation, respectively, were compared for the detection of microbial biomarkers in natural halite from the hyperarid region of the Atacama Desert. Measurements were performed directly on the rock as well as on the homogenized, powdered samples prepared from this material-the effects of this sample preparation and the excitation wavelength employed in the analysis are compared and discussed. From these results, 532 nm excitation was found to be superior for the analysis of powdered specimens due to its high sensitivity toward carotenoids and hence a higher capability for their detection at relatively low concentration in bulk powdered specimens. For the same reason, this wavelength was a better choice for the detection of carotenoids in direct measurements made on the rock samples. The 785 nm excitation wavelength, in contrast, proved to be more sensitive toward the detection of scytonemin.
This work presents a new discussion about the vibrational properties of the carbonate ion displayed in several different environments. The microparameters introduced by cation substitution and ...different crystal lattices in addition to the crystal aggregation are present in the discussion. The work comments on how the Raman modes are affected by these changes by using data obtained with four different laser excitation sources. Raman spectra excited at 1064 nm are reported at 1 cm−1 resolution. New observations and approaches based on the Raman modes highlight the differences observed in the relative intensity and width of the bands. The new data contribute to the understanding of these materials and their spectra, bringing new observations based on the Raman modes. This work presents a new approach highlighting the differences observed in the relative intensity and width of the Raman bands. The results indicate some evidence of the influence of the crystal habit and/or the growth of the mineral itself on the Raman spectrum. In addition, the data show the influence of cation substitution upon Raman bandwidth and the interference of the size of the spot of the laser in the measurement.
Rock‐dwelling microorganisms are frequently exposed to intense UV‐radiation, and thus, they synthesize specialized UV‐protective pigments. In this study, Raman microspectrometry was used for analysis ...of noncarotenoid UV‐protective pigments of dark‐pigmented endolithic colonization found in gypsum outcrops from three areas (Sicily, Poland and Israel). Samples were investigated using 445‐, 532‐ and 780‐nm excitation lasers. Two noncarotenoid UV‐protective pigments scytonemin and gloeocapsin were detected in all studied sites. Major Raman bands of scytonemin were found at around 1593, 1552, 1438 and 1173 cm−1. Gloeocapsin shows characteristic Raman bands similar to anthraquinone‐based parietin of lichens: at 1665, 1575, 1378, 1310 and 465 cm−1. Scytonemin and gloeocapsin are highly specific for cyanobacteria and therefore can be used as biomarkers of certain taxa of cyanobacteria. Detection of such pigments by Raman spectroscopy using three excitation wavelengths allows to gather more information about the composition of endolithic consortia using relatively fast and noninvasive methods and in their natural habitats.
Using the combination of three lasers, 445‐, 532‐ and 780‐nm lasers, two unique UV‐protective pigments—gloeocapsin and scytonemin of gypsum endoliths—were detected. Raman spectra of scytonemin of cyanobacteria that contain diagnostic Raman features were at 1593, 1552, 1438 and 1173 cm−1. Gloeocapsin shows characteristic Raman bands at 1665, 1575, 1378, 1310 and 465 cm−1. Detection of these pigments by Raman spectroscopy provides better information about the composition of endolithic consortia using noninvasive methods and in their natural habitats.
In the first quarter of the 19th Century the factory established at Nantgarw created some of the finest quality porcelain in the world, rivalling that of Sevres, but beset by economic difficulties ...resulting from extraordinarily high kiln losses approaching 90 %, the production which started in 1817 (ceased by 1820) produced the finest translucency ever achieved in Georgian porcelains. An opportunity has arisen to analyse rare Nantgarw porcelain shards excavated archaeologically from the Nantgarw China Works site. Two types of compositions, bone china and silica-rich pastes are identified by Raman and SEM-EDXS analyse, confirming some ancient studies. The spectral data from “sagged” silica-rich shards are interpreted to reveal potential explanations of the manufacturing fault which significantly contributed to the demise of the ceramics factory. Finally, the pigments and glaze used in Nantgarw porcelain decoration have been analysed and identified for the first time.
Mural paintings within the tomb of Setka, Qubbet el-Hawa, in Aswan, Upper Egypt, were investigated using a multi-disciplinary analytical approach (Stereomicroscopy, SEM-EXD and FT-IR spectroscopy). ...The walls of the tomb were hewn from fragile sandstone and covered by a clay plaster, overlaid by two layers of white gypsum plaster. SEM micrographs were indicative of the penetration of fungal mycelium within the pores of the gypsum plaster, forming white encrustations due to the re-precipitation of gypsum. SEM micrographs revealed that the calcification of the gypsum plaster had occurred due to its exposure to a high temperature. The EDX pattern for the white plaster gave the characteristic spectrum of gypsum, the blue pigment was Egyptian blue, the black pigment was magnetite, the white pigment was of gypsum (or anhydrite) and the yellow pigment was limonite. Finally, the FT-IR spectrum of the binder gave the characteristic features of gum Arabic.
Abstract
In this work, Raman spectroscopy and DFT calculations have been used to identify pigments biosynthesized during the ripening of tomatoes. In situ analysis of the exocarp from tomatoes at six ...stages of maturation showed Raman bands attributed mainly to carotenes and flavonoids. The Raman spectra of the exocarp in earlier stages (green and breaker) are rich in carotenoids with nine conjugated double bonds, while later stages (light‐red and red) are dominated by ones with 11 conjugated unsaturation. The Raman structural characterization of carotenoids biosynthesized from the phytoene, phytofluene, to β‐carotene is reported for the first time. Changes in carotenoid composition were observed along with the maturation; however, flavonoids/polyphenols that are concomitantly biosynthesized since the green stage presented the same spectral pattern along the process. Here, we present some clues based on Raman spectroscopy of the chemical synergism between carotenoids and flavonoids in coloring tomatoes.
PDF
