Stellar Astrophysics and Exoplanet Science with the Maunakea Spectroscopic Explorer (MSE)

The Maunakea Spectroscopic Explorer (MSE) is a planned 11.25-m aperture facility with a 1.5 square degree field of view that will be fully dedicated to multi-object spectroscopy. A rebirth of the 3.6m Canada-France-Hawaii Telescope on Maunakea, MSE will use 4332 fibers operating at three different resolving powers (R ~ 2500, 6000, 40000) across a wavelength range of 0.36-1.8mum, with dynamical fiber positioning that allows fibers to match the exposure times of individual objects. MSE will enable spectroscopic surveys with unprecedented scale and sensitivity by collecting millions of spectra per year down to limiting magnitudes of g ~ 20-24 mag, with a nominal velocity precision of ~100 m/s in high-resolution mode. This white paper describes science cases for stellar astrophysics and exoplanet science using MSE, including the discovery and atmospheric characterization of exoplanets and substellar objects, stellar physics with star clusters, asteroseismology of solar-like oscillators and opacity-driven pulsators, studies of stellar rotation, activity, and multiplicity, as well as the chemical characterization of AGB and extremely metal-poor stars.Comment: 31 pages, 11 figures; To appear as a chapter for the Detailed Science Case of the Maunakea Spectroscopic Explore

Heterologous expression and purification of NisA, the precursor peptide of lantibiotic nisin from Lactococcus lactis

The lantibiotic nisin is a ribosomally synthesised and post-translationally modified antimicrobial peptide produced by strains of Lactococcus lactis, and used as safe and natural preservative in food industry. The nisA structural gene encodes ribosomally synthesised and biologically inactive a 57 amino acid precursor peptide (NisA) which undergoes several post-translational modifications. In this study, we report the expression of precursor nisin as a His6-tagged peptide in Escherichia coli and its purification using a nickel affinity column. The technique of spliced-overlap extension PCR was used to amplify the nisA gene and the T7 promoter region of pET-15b vector. This approach was used to introduce six histidine residues at the C-terminus of prenisin. The identity of the expressed peptide was confirmed by N-terminal sequencing. The expressed His-tagged prenisin was purified under denaturing conditions, and named as prenisin-His6. The purified prenisin-His6 was analyzed by SDS-PAGE, Western blotting and mass spectroscopy. These results showed that the nisin precursor peptide can be successfully produced using an E. coli expression system

Detection of genes for periplasmic nitrate reductase in nitrate respiring bacteria and in community DNA

A nested PCR primed by four degenerate oligonucleotides was developed for the specific amplification of sequences from the napA gene encoding the periplasmic nitrate reductase. This approach was used to amplify fragments of the napA gene from 10 Pseudomonas species and one Moraxella sp., previously shown to be able to express the periplasmic nitrate reductase activity, from Rhodobacter capsulatus and from community DNA extracted from a fresh-water sediment. Amino acid sequences encoded by the napA fragments were compared to one another and to the corresponding regions of related enzymes. This comparison indicates that the amplification protocol is specific for its intended target. The napA sequences amplified from community DNA were tightly clustered, which may indicate a degree of homogeneity in the sediment community. All tested Gram-negative strains capable of aerobic nitrate respiration were found to have periplasmic nitrate reductase genes. However, some strains which have and express the genes are incapable of aerobic nitrate respiration. The PCR primers and amplification protocols described will be useful in future studies of nitrate respiring populations

Covid-19 infection in children with cancer after the first wave in Turkey: A study of the Turkish pediatric oncology (TPOG) and hematology (TPHD) societies

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