A new semi-quantitative Surface-Enhanced Raman Spectroscopy (SERS) method for detection of maleimide (2,5-pyrroledione) with potential application to astrobiology

Nitrogen-containing heterocyclic compounds are fundamental biochemical components of all life on Earth and, presumably, life elsewhere in our solar system. Detection and characterization of these compounds by traditional solvent extraction, chromatographic separation, and GC–MS analysis require more sample mass than will be available from samples returned to Earth from Mars. With its small sample mass requirement, Surface Enhanced Raman Spectroscopy could be an appropriate technique for analysis of returned samples. We have developed a SERS method for the detection of maleimide (2,5-pyrroledione), an N-containing heterocycle with a structure that is widespread in biochemicals. This semi-quantitative methodology accurately determines maleimide concentration in the range from 60 µg/mL to 120 µg/mL. We present a maleimide SERS standard spectrum which will be useful as a reference for future works. The present work demonstrates an easy, accurate, and effective method for the non-destructive qualitative and semi-quantitative study of maleimide as a first step toward developing a method for analysis of related compounds

Episodic photic zone euxinia in the northeastern Panthalassic Ocean during the end-Triassic extinction

Severe changes in ocean redox, nutrient cycling, and marine productivity accompanied most Phanerozoic mass extinctions. However, evidence for marine photic zone euxinia (PZE) as a globally important extinction mechanism for the end-Triassic extinction (ETE) is currently lacking. Fossil molecular (biomarker) and nitrogen isotopic records from a sedimentary sequence in western Canada provide the first conclusive evidence of PZE and disrupted biogeochemistry in neritic waters of the Panthalassic Ocean during the end Triassic. Increasing water-column stratification and deoxygenation across the ETE led to PZE in the Early Jurassic, paralleled by a perturbed nitrogen cycle and ecological turnovers among noncalcifying groups, including eukaryotic algae and prokaryotic plankton. If such conditions developed widely in the Panthalassic Ocean, PZE might have been a potent mechanism for the ETE

Microbial community composition and dolomite formation in the hypersaline microbial mats of the Khor Al-Adaid sabkhas, Qatar

The Khor Al-Adaid sabkha in Qatar is among the rare extreme environments on Earth where it is possible to study the formation of dolomite-a carbonate mineral whose origin remains unclear and has been hypothetically linked to microbial activity. By combining geochemical measurements with microbiological analysis, we have investigated the microbial mats colonizing the intertidal areas of sabhka. The main aim of this study was to identify communities and conditions that are favorable for dolomite formation. We inspected and sampled two locations. The first site was colonized by microbial mats that graded vertically from photo-oxic to anoxic conditions and were dominated by cyanobacteria. The second site, with higher salinity, had mats with an uppermost photo-oxic layer dominated by filamentous anoxygenic photosynthetic bacteria (FAPB), which potentially act as a protective layer against salinity for cyanobacterial species within the deeper layers. Porewater in the uppermost layers of the both investigated microbial mats was supersaturated with respect to dolomite. Corresponding to the variation of the microbial community's vertical structure, a difference in crystallinity and morphology of dolomitic phases was observed: dumbbell-shaped proto-dolomite in the mats dominated by cyanobacteria and rhombohedral ordered-dolomite in the mat dominated by FAPB.This publication was made possible by NPRP Grant 7-443-1-083 from the Qatar National Research Fund (a member of Qatar Foundation). MD was supported by the National Sciences and Engineering Research Council of Canada (NSERC Discovery Grant) and the Canada Foundation for Innovation and Ontario Research Fund (Leaders Opportunity Fund, Grant Number 22404). The statements made herein are solely the responsibility of the authors. The authors would like to acknowledge Oleksandra Kaskun for performing alkalinity measurements, Dr. K. Tait at the Royal Ontario Museum for use of XRD and Sal Boccia at the Ontario Centre for the Characterizations of Advanced Materials (OCCAM) for the assistance with SEM imaging.Scopu