The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Jorune Sakalauskaite - One of the best experts on this subject based on the ideXlab platform.
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shell palaeoproteomics first application of peptide mass fingerprinting for the rapid identification of mollusc shells in archaeology
Journal of Proteomics, 2020Co-Authors: Jorune Sakalauskaite, Frederic Marin, Barbara Pergolizzi, Beatrice DemarchiAbstract:Molluscs were one of the most widely-used natural resources in the past, and their shells are abundant among archaeological findings. However, our knowledge of the variety of shells that were circulating in prehistoric times (and thus their socio-economic and cultural value) is scarce due to the difficulty of achieving taxonomic determination of fragmented and/or worked remains. This study aims to obtain molecular barcodes based on peptide mass fingerprints (PMFs) of intracrystalline proteins, in order to obtain shell identification. Palaeoproteomic applications on shells are challenging, due to low concentration of molluscan proteins and an incomplete understanding of their sequences. We explore different approaches for protein extraction from small-size Samples (<20 mg), followed by MALDI-TOF-MS analysis. The SP3 (single-pot, solid-Phase) Sample preparation method was found to be the most successful in retrieving the intracrystalline protein fraction from seven molluscan shell taxa, which belong to different phylogenetic groups, possess distinct microstructures and are relevant for archaeology. Furthermore, all the shells analysed, including a 7000-year-old specimen of the freshwater bivalve Pseudunio, yielded good-quality distinctive spectra, demonstrating that PMFs can be used for shell taxon determination. Our work suggests good potential for large-scale screening of archaeological molluscan remains. SIGNIFICANCE: We characterise for the first time the peptide mass fingerprints of the intracrystalline shell protein fraction isolated from different molluscan taxa. We demonstrate that these proteins yield distinctive PMFs, even for shells that are phylogenetically related and/or that display similar microstructures. Furthermore, we extend the range of Sample preparation approaches for "shellomics" by testing the SP3 method, which proved to be well-suited to shell protein extraction from small-size and protein-poor Samples. This work thus lays the foundations for future large-scale applications for the identification of mollusc shells and other invertebrate remains from the archaeological and palaeontological records.
Michael Stipp - One of the best experts on this subject based on the ideXlab platform.
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potential of full pattern fit methods for the texture analysis of geological materials implications from texture measurements at the recently upgraded neutron time of flight diffractometer skat
Journal of Applied Crystallography, 2014Co-Authors: Ruth Keppler, Klaus Ullemeyer, Jan H Behrmann, Michael StippAbstract:The application of Rietveld texture analysis (RTA) to time-of-flight (TOF) neutron diffraction data allows complex materials with many diffraction peaks to be investigated, for example, rocks composed of different minerals. At the recently upgraded SKAT texture diffractometer at the JINR in Dubna (Russia), which provides three alternative multidetector systems, resolution and accessible range of lattice d spacings can be adapted to Sample requirements. In order to infer the optimum experimental setup and the reliability of texture estimates from complicated TOF patterns, the influence of counting statistics and various spectral resolutions on texture deconvolution was investigated. Comparing the results obtained at different resolutions and from different sections of the d patterns indicates that the textures of a four-Phase Sample can be determined, but using a section at small d spacings with a larger number of peak overlaps leads to smoother textures. A complex seven-Phase Sample shows orientation differences in addition to the smoothing effect. Weak textures and textures of the minor rock constituents are inaccurate owing to multiple peak overlaps. Consequently, good resolution is essential for RTA on such Samples. Grid thinning tests confirmed that no more than 150 diffraction spectra are needed to characterize the texture of a monomineralic Sample, and approximately 350 spectra are sufficient for a four-Phase Sample. The irregular grid point arrangement caused by the SKAT geometry has no negative consequences.
Beatrice Demarchi - One of the best experts on this subject based on the ideXlab platform.
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shell palaeoproteomics first application of peptide mass fingerprinting for the rapid identification of mollusc shells in archaeology
Journal of Proteomics, 2020Co-Authors: Jorune Sakalauskaite, Frederic Marin, Barbara Pergolizzi, Beatrice DemarchiAbstract:Molluscs were one of the most widely-used natural resources in the past, and their shells are abundant among archaeological findings. However, our knowledge of the variety of shells that were circulating in prehistoric times (and thus their socio-economic and cultural value) is scarce due to the difficulty of achieving taxonomic determination of fragmented and/or worked remains. This study aims to obtain molecular barcodes based on peptide mass fingerprints (PMFs) of intracrystalline proteins, in order to obtain shell identification. Palaeoproteomic applications on shells are challenging, due to low concentration of molluscan proteins and an incomplete understanding of their sequences. We explore different approaches for protein extraction from small-size Samples (<20 mg), followed by MALDI-TOF-MS analysis. The SP3 (single-pot, solid-Phase) Sample preparation method was found to be the most successful in retrieving the intracrystalline protein fraction from seven molluscan shell taxa, which belong to different phylogenetic groups, possess distinct microstructures and are relevant for archaeology. Furthermore, all the shells analysed, including a 7000-year-old specimen of the freshwater bivalve Pseudunio, yielded good-quality distinctive spectra, demonstrating that PMFs can be used for shell taxon determination. Our work suggests good potential for large-scale screening of archaeological molluscan remains. SIGNIFICANCE: We characterise for the first time the peptide mass fingerprints of the intracrystalline shell protein fraction isolated from different molluscan taxa. We demonstrate that these proteins yield distinctive PMFs, even for shells that are phylogenetically related and/or that display similar microstructures. Furthermore, we extend the range of Sample preparation approaches for "shellomics" by testing the SP3 method, which proved to be well-suited to shell protein extraction from small-size and protein-poor Samples. This work thus lays the foundations for future large-scale applications for the identification of mollusc shells and other invertebrate remains from the archaeological and palaeontological records.
Mark E Smith - One of the best experts on this subject based on the ideXlab platform.
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quantification of crystalline Phases and measurement of phosphate chain lengths in a mixed Phase Sample by 31p refocused inadequate mas nmr
Chemical Physics Letters, 2008Co-Authors: Luke A Odell, Paul Guerry, Alan Wong, Ensanya Abou A Neel, Tran N Pham, Jonathan C Knowles, Steven P Brown, Mark E SmithAbstract:A P-31 refocused INADEQUATE pulse sequence has been used in combination with XRD to identify and quantify the crystalline Phases present in a ternary sodium calcium phosphate ceramic of composition (CaO)(0.4)(Na2O)(0.1)(P2O5)(0.5). Both the NMR and XRD identified the two main Phases present as NaCa(PO3)(3) and beta-Ca(PO3)(2). A third unidentified calcium phosphate Phase was also observed by MAS NMR, featuring a chain of six crystallographically distinct PO4 units, the P-31 MAS NMR chemical shifts of which have been identified in the correct sequence along the chain. (C) 2008 Elsevier B.V. All rights reserved.
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solid state nmr characterisation of the thermal transformation of a hungarian white illite
Solid State Nuclear Magnetic Resonance, 2005Co-Authors: Donna L Carroll, Thomas F Kemp, T J Bastow, Mark E SmithAbstract:1H, 27Al, 29Si and 39K solid-state NMR are reported from a Hungarian illite 2:1 clay for Samples heated up 1600 °C. This single-Phase Sample has a small amount of aluminium substitution in the silica layer and very low iron-content (0.4 wt%). Thermal analysis shows several events that can be related to features in the NMR spectra, and hence changes in the atomic scale structure. As dehydroxylation occurs there is increasing AlO4 and AlO5-contents. The silica and gibbsite layers become increasingly separated as the dehydroxylation progresses. Between 900 and 1000 °C the silica layer forms a potassium aluminosilicate glass. The gibbsite-layer forms spinel/γ-Al2O3 and some aluminium-rich mullite. Then on heating to 1600 °C changes in the 29Si and 27Al MAS NMR spectra are consistent with the aluminosilicate glass increasing its aluminium-content, the amount of mullite increasing probably with its silicon-content also increasing, and some α-Al2O3 forming.
G M Luke - One of the best experts on this subject based on the ideXlab platform.
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absence of superconductivity in single Phase cafe 2 as 2 under hydrostatic pressure
Physical Review B, 2009Co-Authors: A A Aczel, T J Williams, S L Budko, P C Canfield, G M LukeAbstract:Recent high-pressure studies found that structural/magnetic Phase transitions are very pressure sensitive in ${\text{CaFe}}_{2}{\text{As}}_{2}$ and that superconductivity can be achieved under modest pressure, although details of the sharpness and temperature of transitions vary between liquid medium and gas medium measurements. To better understand this issue, we performed high-pressure susceptibility and transport studies on ${\text{CaFe}}_{2}{\text{As}}_{2}$, using helium as the pressure medium. The signatures of the transitions to the low-temperature orthorhombic and collapsed tetragonal Phases remained exceptionally sharp, and no signature of bulk superconductivity was found under our hydrostatic conditions. Our results suggest that superconductivity in ${\text{CaFe}}_{2}{\text{As}}_{2}$ is associated with a low-temperature, multicrystallographic-Phase Sample that is the result of nonhydrostatic conditions associated with the combination of a first-order structural Phase transition and frozen liquid media.