Perspective from a Younger Generation -- The Astro-Spectroscopy of Gisbert Winnewisser

Gisbert Winnewisser's astronomical career was practically coextensive with the whole development of molecular radio astronomy. Here I would like to pick out a few of his many contributions, which I, personally, find particularly interesting and put them in the context of newer results.Comment: 14 pages. (Co)authored by members of the MPIfR (Sub)millimeter Astronomy Group. To appear in the Proceedings of the 4th Cologne-Bonn-Zermatt-Symposium "The Dense Interstellar Medium in Galaxies" eds. S. Pfalzner, C. Kramer, C. Straubmeier, & A. Heithausen (Springer: Berlin

A Universal Power-law Prescription for Variability from Synthetic Images of Black Hole Accretion Flows

We present a framework for characterizing the spatiotemporal power spectrum of the variability expected from the horizon-scale emission structure around supermassive black holes, and we apply this framework to a library of general relativistic magnetohydrodynamic (GRMHD) simulations and associated general relativistic ray-traced images relevant for Event Horizon Telescope (EHT) observations of Sgr A*. We find that the variability power spectrum is generically a red-noise process in both the temporal and spatial dimensions, with the peak in power occurring on the longest timescales and largest spatial scales. When both the time-averaged source structure and the spatially integrated light-curve variability are removed, the residual power spectrum exhibits a universal broken power-law behavior. On small spatial frequencies, the residual power spectrum rises as the square of the spatial frequency and is proportional to the variance in the centroid of emission. Beyond some peak in variability power, the residual power spectrum falls as that of the time-averaged source structure, which is similar across simulations; this behavior can be naturally explained if the variability arises from a multiplicative random field that has a steeper high-frequency power-law index than that of the time-averaged source structure. We briefly explore the ability of power spectral variability studies to constrain physical parameters relevant for the GRMHD simulations, which can be scaled to provide predictions for black holes in a range of systems in the optically thin regime. We present specific expectations for the behavior of the M87* and Sgr A* accretion flows as observed by the EHT

High-throughput micro-characterization of RNA-protein interactions

12 p.-2 fig.-2 tabMany cellular processes depend on and are regulated by nucleic acid-protein interactions. In particular, RNA-binding proteins (RBPs) are involved in transcription, translation, modulating RNA polymerase activity, and stabilizing protein-RNA complexes. Furthermore, RBPs participate in the development of pathologies such as cancer and viral infections, and their dysfunction leads to mutations and the aberrant expression of noncoding RNAs. Therefore, the study of RNA-protein interactions represents a central issue for biology and biomedicine. While many valuable insights have been obtained from electrophoretic mobility shift assays (EMSA) and immunoprecipitation (IP), these standard methods suffer from two main limitations: insufficient sensitivity to capture low concentration RBP-RNA complexes in vitro and identification of interactions in vivo. In recent years, high-throughput (HTP) platforms have emerged that combine methodological improvements over conventional techniques with more sensitive detection systems, thereby catalyzing the simultaneous probing and analysis of a vast amount of RBP-RNA interactions by cellular proteomics and interactomics approaches. In this chapter, we summarize a selection of state-of-the-art in vitro, in vivo, and computational HTP platforms for the discovery and characterization of RNA-protein interactions. We also reflect on the wealth of information obtained by the structural analysis of RBPs and their RNA-binding domains as a valuable resource for the rational design and implementation of new RNA-binding discovery platforms.MCV has received funding from the Spanish Ministerio de Economía y Competitividad (CTQ2015-66206-C2-2-R and SAF2015-72961-EXP) and the Regional Government of Madrid (S2017/BMD-3673).Peer reviewe

β2-microglobulin is a systemic pro-aging factor that impairs cognitive function and neurogenesis

Aging drives cognitive and regenerative impairments in the adult brain, increasing susceptibility to neurodegenerative disorders in healthy individuals. Experiments using heterochronic parabiosis, in which the circulatory systems of young and old animals are joined, indicate that circulating pro-aging factors in old blood drive aging phenotypes in the brain. Here we identify β2-microglobulin (B2M), a component of major histocompatibility complex class 1 (MHC I) molecules, as a circulating factor that negatively regulates cognitive and regenerative function in the adult hippocampus in an age-dependent manner. B2M is elevated in the blood of aging humans and mice, and it is increased within the hippocampus of aged mice and young heterochronic parabionts. Exogenous B2M injected systemically, or locally in the hippocampus, impairs hippocampal-dependent cognitive function and neurogenesis in young mice. The negative effects of B2M and heterochronic parabiosis are, in part, mitigated in the hippocampus of young transporter associated with antigen processing 1 (Tap1)-deficient mice with reduced cell surface expression of MHC I. The absence of endogenous B2M expression abrogates age-related cognitive decline and enhances neurogenesis in aged mice. Our data indicate that systemic B2M accumulation in aging blood promotes age-related cognitive dysfunction and impairs neurogenesis, in part via MHC I, suggesting that B2M may be targeted therapeutically in old age