Revisiting Ediacaran sulfur isotope chemostratigraphy with in situ nanoSIMS analysis of sedimentary pyrite

Reconstructions of ancient sulfur cycling and redox conditions commonly rely on sulfur isotope measurements of sedimentary rocks and minerals. Ediacaran strata (635–541 Ma) record a large range of values in bulk sulfur isotope difference (Δ34S) between carbonate-associated sulfate (δ34SCAS) and sedimentary pyrite (δ34Spy), which has been interpreted as evidence of marine sulfate reservoir size change in space and time. However, bulk δ34Spy measurements could be misleading because pyrite forms under syngenetic, diagenetic, and metamorphic conditions, which differentially affect its isotope signature. Fortunately, these processes also impart recognizable changes in pyrite morphology. To tease apart the complexity of Ediacaran bulk δ34Spy measurements, we used scanning electron microscopy and nanoscale secondary ion mass spectrometry to probe the morphology and geochemistry of sedimentary pyrite in an Ediacaran drill core of the South China block. Pyrite occurs as both framboidal and euhedral to subhedral crystals, which show largely distinct negative and positive δ34Spy values, respectively. Bulk δ34Spy measurements, therefore, reflect mixed signals derived from a combination of syndepositional and diagenetic processes. Whereas euhedral to subhedral crystals originated during diagenesis, the framboids likely formed in a euxinic seawater column or in shallow marine sediment. Although none of the forms of pyrite precisely record seawater chemistry, in situ framboid measurements may provide a more faithful record of the maximum isotope fractionation from seawater sulfate. Based on data from in situ measurements, the early Ediacaran ocean likely contained a larger seawater sulfate reservoir than suggested by bulk analyses.

Supplemental Material: Revisiting Ediacaran sulfur isotope chemostratigraphy with in situ nanoSIMS analysis of sedimentary pyrite

Geological background, analytical methods and results.

Supplemental Material: Revisiting Ediacaran sulfur isotope chemostratigraphy with in situ nanoSIMS analysis of sedimentary pyrite

Geological background, analytical methods and results.

NanoSIMS Imaging and Analysis in Materials Science

High-resolution SIMS analysis can be used to explore a wide range of problems in material science and engineering materials, especially when chemical imaging with good spatial resolution (50–100 nm) can be combined with efficient detection of light elements and precise separation of isotopes and isobaric species. Here, applications of the NanoSIMS instrument in the analysis of inorganic materials are reviewed, focusing on areas of current interest in the development of new materials and degradation mechanisms under service conditions. We have chosen examples illustrating NanoSIMS analysis of grain boundary segregation, chemical processes in cracking, and corrosion of nuclear components. An area where NanoSIMS analysis shows potential is in the localization of light elements, in particular, hydrogen and deuterium. Hydrogen embrittlement is a serious problem for industries where safety is critical, including aerospace, nuclear, and oil/gas, so it is imperative to know where in the microstructure hydrogen is located. By charging the metal with deuterium, to avoid uncertainty in the origin of the hydrogen, the microstructural features that can trap hydrogenic species, such as precipitates and grain and phase boundaries, can be determined by NanoSIMS analysis on a microstructurally relevant scale.

A platinum(II)-napthalimide probe for sub-cellular imaging of bacteria

There is a lack of molecular probes for imaging bacteria, in comparison to the array of such tools available for the imaging of mammalian cells. A platinum(II)-naphthalimide molecule has been developed as a small molecule probe for bacterial imaging, designed to have the potential for correlative imaging. The naphthalimide moiety acts as a luminescent probe for super-resolution microscopy, functioning independently of the platinum(II) centre which enabled visualisation of the complex with ion nanoscopy. Structured illumination microscopy (SIM) imaging on live <i>Bacillus cereus</i> confirmed the suitability of the probe for super-resolution microscopy. NanoSIMS analysis was used to monitor the uptake of the platinum(II) complex within the bacteria and proved the multimodal action of the probe. The successful combination of these two probe moieties introduces a platform that could lead to a versatile range of correlative probes for bacteria.<br>

A platinum(II)-napthalimide probe for sub-cellular imaging of bacteria

There is a lack of molecular probes for imaging bacteria, in comparison to the array of such tools available for the imaging of mammalian cells. A platinum(II)-naphthalimide molecule has been developed as a small molecule probe for bacterial imaging, designed to have the potential for correlative imaging. The naphthalimide moiety acts as a luminescent probe for super-resolution microscopy, functioning independently of the platinum(II) centre which enabled visualisation of the complex with ion nanoscopy. Structured illumination microscopy (SIM) imaging on live <i>Bacillus cereus</i> confirmed the suitability of the probe for super-resolution microscopy. NanoSIMS analysis was used to monitor the uptake of the platinum(II) complex within the bacteria and proved the multimodal action of the probe. The successful combination of these two probe moieties introduces a platform that could lead to a versatile range of correlative probes for bacteria.<br>

A Platinum(II) Based Correlative Probe for Bacteria

There is a lack of molecular probes for imaging bacteria, in comparison to the array of such tools available for the imaging of mammalian cells. This is especially so for correlative probes, which are proving to be powerful tools for enhancing the imaging of live cells. In this work a platinum(II)-naphthalimide molecule has been developed to extend small molecule correlative probes to bacterial imaging. The probe was designed to exploit the naphthalimide moiety as a luminescent probe for super-resolution microscopy, with the platinum(II) centre enabling visualisation of the complex with ion nanoscopy. Photophysical characterisation and theoretical studies confirmed that the emission properties of the naphthalimide are not altered by the platinum(II) centre. Structured illumination microscopy (SIM) imaging on live <i>Bacillus cereus</i>revealed that the platinum(II) centre does not change the sub-cellular localisation of the naphthalimide, and confirmed the suitability of the probe for super-resolution microscopy. NanoSIMS analysis of the sample was used to monitor the uptake of the platinum(II) complex within the bacteria and proved the correlative action of the probe. The successful combination of these two probe moieties with no perturbation of their individual detection introduces a platform for a versatile range of new correlative probes for bacteria.