Linda C. Prinsloo

The dehydration of phosphates monitored by DSC/TGA and in situ Raman spectroscopy

Abstract Phosphates can be thermally dehydrated to polyphosphates or metaphosphates. This is an important reaction in the preparation of glasses, catalysts and flame retardants. In this study, we have monitored the dehydration process of potassium and sodium dihydrogen phosphates, using in situ Raman spectroscopy, thermal analysis, X-ray powder diffraction and infrared spectroscopy. We obtained a good correlation between the thermal data and the structural phase transitions observed during the reactions, using Raman and infrared spectroscopy. Deuteration of the samples assisted us in assigning some of the vibrational bands.

Unusual coloration in scarabaeid beetles

In this paper we investigate the reflection of circularly polarized light from the exocuticle of the scarabaeid beetle Gymnopleurus virens. Reflection spectra are deeply modulated, exhibiting a number of relatively narrow well-defined peaks, which differ from previously studied specimens. By comparing model calculations and electron microscopy work with the recorded spectra, we can propose the presence of specific structural defects responsible for the unusual spectra.

Functional implications of temperature‐correlated colour polymorphism in an iridescent, scarabaeine dung beetle

Abstract 1. In many Coleoptera, iridescent colouration is generated by exoskeleton ultra‐structure, within which multilayer interference reflects only certain wavelengths. Published work indicates that the colour polymorphism shown by some iridescent beetles is under genetic control. However, the present study suggests environmental involvement in the polymorphic southern African dung beetle, Gymnopleurus humanus Macleay.

Optical spectroscopy of silicates and glasses

The recent progress, in the use of optical/vibrational spectroscopy for the identification and understanding of the nanostructure of amorphous and crystalline silicates, is reviewed. The focus of the discussion is on Raman spectroscopy and we present experimental procedures and models. Cultural heritage case studies illustrate the potential of the technique, including the identification of fakes/copies and quantification of the corrosion degree and resulting dating capability.

A micro-Raman spectroscopic investigation of leukemic U-937 cells treated with Crotalaria agatiflora Schweinf and the isolated compound madurensine.

In South Africa traditional medicine plays an important role in primary health care and therefore it is very important that the medicinal use of plants is scientifically tested for toxicity and effectiveness. It was established that the ethanolic extract of the leaves of Crotalaria agatiflora, as well as the isolated compound madurensine, is moderately toxic against leukemic U-937 cells. Light microscopic investigations indicated that symptoms of cell death are induced during treatments, but flow cytometry analysis of treated cells, using annexin-V and propidium iodide, showed that apoptosis and necrosis are insignificantly induced. The Raman results suggested that protein extraction and DNA melting occur in the cells during treatment with the ethanolic extracts (IC(50) value 73.9 μg/mL), drastically changing the molecular content of the cells. In contrast, treatment with madurensine (IC(50) value 136.5 μg/mL), an isolated pyrrolizidine alkaloid from the ethanolic extract of the leaves, did not have the same effect. The results are also compared to that of cells treated with actinomycin D, a compound known to induce apoptosis. The investigation showed that micro-Raman spectroscopy has great promise to be used for initial screening of samples to determine the effects of different treatments on cancerous cell lines together with conventional methods. The results highlight the fact that for many natural products used for medicinal purposes, the therapeutic effect of the crude plant extract tends to be significantly more effective than the particular action of its individual constituents.

Fourier transform infrared spectroscopy discloses different types of cell death in flow cytometrically sorted cells

Fourier Transform Infrared (FTIR) spectroscopy is a label free methodology showing promise in characterizing different types of cell death. Cervical adenocarcinoma (HeLa) and African monkey kidney (Vero) cells were treated with a necrosis inducer (methanol), novel apoptotic inducers (diphenylphosphino gold (I) complexes) and positive control, auranofin. Following treatment, cells stained with annexin-V and propidium iodide were sorted using a Fluorescence Activated Cell Sorter (FACS Aria) to obtain populations consisting of either viable, necrotic or apoptotic cells. Transmission Electron Microscopy confirmed successful sorting of all three populations. Four bands were identified which could discriminate between viable and necrotic cells namely 989 cm(-1), 2852 cm(-1), 2875 cm(-1) and 2923 cm(-1). In HeLa cells viable and induced apoptosis could be distinguished by 1294 cm(-1), while four bands were different in Vero cells namely; 1626 cm(-1), 1741 cm(-1), 2852 cm(-1) 2923 cm(-1). Principal Component Analysis showed separation between the different types of cell death and the loadings plots indicated an increase in an additional band at 1623 cm(-1) in dead cells. FTIR spectroscopy can be developed into an invaluable tool for the assessment of specific types of chemically induced cell death with notably different molecular signatures depending on whether the cells are cancerous and mechanism of cell death.

Cellular injury evidenced by impedance technology and infrared microspectroscopy

Fourier Transform Infrared (FTIR) spectroscopy is finding increasing biological application, for example in the analysis of diseased tissues and cells, cell cycle studies and investigating the mechanisms of action of anticancer drugs. Cancer treatment studies routinely define the types of cell-drug responses as either total cell destruction by the drug (all cells die), moderate damage (cell deterioration where some cells survive) or reversible cell cycle arrest (cytostasis). In this study the loss of viability and related chemical stress experienced by cells treated with the medicinal plant, Plectranthus ciliatus, was investigated using real time cell electronic sensing (RT-CES) technology and FTIR microspectroscopy. The use of plants as medicines is well established and ethnobotany has proven that crude extracts can serve as treatments against various ailments. The aim of this study was to determine whether FTIR microspectroscopy would successfully distinguish between different types of cellular injury induced by a potentially anticancerous plant extract. Cervical adenocarcinoma (HeLa) cells were treated with a crude extract of Pciliatus and cells monitored using RT-CES to characterize the type of cellular responses induced. Cell populations were then investigated using FTIR microspectroscopy and statistically analysed using One-way Analysis of Variance (ANOVA) and Principal Component Analysis (PCA). The plant extract and a cancer drug control (actinomycin D) induced concentration dependent cellular responses ranging from nontoxic, cytostatic or cytotoxic. Thirteen spectral peaks (915cm(-)(1), 933cm(-)(1), 989cm(-)(1), 1192cm(-)(1), 1369cm(-)(1), 1437cm(-)(1), 1450cm(-)(1), 1546cm(-)(1), 1634cm(-)(1), 1679cm(-)(1) 1772cm(-)(1), 2874cm(-)(1) and 2962cm(-)(1)) associated with cytotoxicity were significantly (p value<0.05, one way ANOVA, Tukey test, Bonferroni) altered, while two of the bands were also indicative of early stress related responses. In PCA, poor separation between nontoxic and cytostatic responses was evident while clear separation was linked to cytotoxicity. RT-CES detected morphological changes as indicators of cell injury and could distinguish between viable, cytostatic and cytotoxic responses. FTIR microspectroscopy confirmed that cytostatic cells were viable and could still recover while also describing early cellular stress related responses on a molecular level.

Photoluminescence and Raman spectroscopy of Mg-doped GaN; as grown, hydrogen implanted and annealed

Abstract Hydrogen-ion implantation was studied for Mg-doped hexagonal GaN grown on sapphire. Low temperature photoluminescence spectroscopy (PL) shows two significant features; the implantation-annealing induced yellow band (YL) and a remarkable sharp excitonic peak. In the region 1.73–1.79 eV well resolved optical transitions were observed, which resemble the well known R1 and R2 emission bands from Cr3+ in Al2O3 (ruby). Structural and electronic changes were monitored by inelastic light scattering (ILS) spectroscopy. At high implantation dose and high annealing temperature we observed well resolved bands at 320, 380 and 640 cm−1. The latter band ‘splits’ into 645 and 672 bands at the highest implantation dose. Additionally, implantation-annealing induced band was observed at 430 cm−1. This band was not observed before. Besides these, four of the six Raman allowed modes are present in the spectra: 2A1, E1 and E2. Second order Raman spectroscopy yields several bands in the region 860–1470 cm−1. On the high energy side of the spectra, we monitor luminescence bands at 1.878, 1.85, 1.836 eV and for the first time observed a 1.8 eV band. Using a group-theoretical approach we assign symmetries of the first order phonons at k=0 as well as some experimentally observed second order symmetry allowed modes.

Metallodrug induced apoptotic cell death and survival attempts are characterizable by Raman spectroscopy

Chrysotherapeutics are under investigation as new or additional treatments for different types of cancers. In this study, gold complexes were investigated for their anticancer potential using Raman spectroscopy. The aim of the study was to determine whether Raman spectroscopy could be used for the characterization of metallodrug-induced cell death. Symptoms of cell death such as decreased peak intensities of proteins bonds and phosphodiester bonds found in deoxyribose nucleic acids were evident in the principal component analysis of the spectra. Vibrational bands around 761 cm−1 and 1300 cm−1 (tryptophan, ethanolamine group, and phosphatidylethanolamine) and 1720 cm−1 (ester bonds associated with phospholipids) appeared in the Raman spectra of cervical adenocarcinoma (HeLa) cells after metallodrug treatment. The significantly (p < 0.05, one way analysis of variance) increased intensity of phosphatidylethanolamine after metallodrug treatment could be a molecular signature of induced apoptosis since both th...

Responses of South African Agate and Chalcedony When Heated Experimentally, and the Broader Implications for Heated Archaeological Minerals

ABSTRACT Here we present a database of responses by South African agate and chalcedony to heat treatment. This will assist analyses of heated stone tools not only in South African archaeological sites, but wherever heated agate and chalcedony pieces were knapped. The minerals are abundant worldwide. To replicate potential heating methods during the Stone Age we placed some minerals in a wood fire, some under coals, and others were buried in sediments beneath fires. Thermal responses include lustrous flaked surfaces, pot lid fractures, semi-circular internal fractures, rough internal surfaces, and crazing. Aerobic heating is implied by pot lid fractures. To explain the thermal responses we analyzed the minerals using X-ray fluorescence, Raman spectroscopy, and carbon and sulfur analyses. Our chalcedony contains more water and impurities than agate, making it more vulnerable to thermal damage. Our method of combining field experiments with chemical analyses has global applications even though we expect that mineral components of agate and chalcedony will vary slightly in different parts of the world.