The edge of galaxy formation III: The effects of warm dark matter on Milky Way satellites and field dwarfs

In this third paper of the series, we investigate the effects of warm dark matter with a particle mass of $m_\mathrm{WDM}=3\,\mathrm{keV}$ on the smallest galaxies in our Universe. We present a sample of 21 hydrodynamical cosmological simulations of dwarf galaxies and 20 simulations of satellite-host galaxy interaction that we performed both in a Cold Dark Matter (CDM) and Warm Dark Matter (WDM) scenario. In the WDM simulations, we observe a higher critical mass for the onset of star formation. Structure growth is delayed in WDM, as a result WDM haloes have a stellar population on average two Gyrs younger than their CDM counterparts. Nevertheless, despite this delayed star formation, CDM and WDM galaxies are both able to reproduce the observed scaling relations for velocity dispersion, stellar mass, size, and metallicity at $z=0$. WDM satellite haloes in a Milky Way mass host are more susceptible to tidal stripping due to their lower concentrations, but their galaxies can even survive longer than the CDM counterparts if they live in a dark matter halo with a steeper central slope. In agreement with our previous CDM satellite study we observe a steepening of the WDM satellites' central dark matter density slope due to stripping. The difference in the average stellar age for satellite galaxies, between CDM and WDM, could be used in the future for disentangling these two models.Comment: 10 pages, 11 figures, accepted for publication on MNRA

Interplay of ‘induced fit’ and preorganization in the ligand induced folding of the aptamer domain of the guanine binding riboswitch

Riboswitches are highly structured elements in the 5′-untranslated regions (5′-UTRs) of messenger RNA that control gene expression by specifically binding to small metabolite molecules. They consist of an aptamer domain responsible for ligand binding and an expression platform. Ligand binding in the aptamer domain leads to conformational changes in the expression platform that result in transcription termination or abolish ribosome binding. The guanine riboswitch binds with high-specificity to guanine and hypoxanthine and is among the smallest riboswitches described so far. The X-ray-structure of its aptamer domain in complex with guanine/hypoxanthine reveals an intricate RNA-fold consisting of a three-helix junction stabilized by long-range base pairing interactions. We analyzed the conformational transitions of the aptamer domain induced by binding of hypoxanthine using high-resolution NMR-spectroscopy in solution. We found that the long-range base pairing interactions are already present in the free RNA and preorganize its global fold. The ligand binding core region is lacking hydrogen bonding interactions and therefore likely to be unstructured in the absence of ligand. Mg(2+)-ions are not essential for ligand binding and do not change the structure of the RNA-ligand complex but stabilize the structure at elevated temperatures. We identified a mutant RNA where the long-range base pairing interactions are disrupted in the free form of the RNA but form upon ligand binding in an Mg(2+)-dependent fashion. The tertiary interaction motif is stable outside the riboswitch context

Brent jord: langsiktige politiske konsekvenser av nedbrenning og tvangsevakuering i Nord-Troms og Finnmark

Høsten 1944 iverksatte den tyske okkupasjonsmakten operasjon «Nordlicht», også kjent som «den brente jords taktikk». De materielle ødeleggelsene og de menneskelige omkostningene var enorme. Selve ødeleggelsene og operasjonen er godt dokumentert, men ikke de langsiktige samfunnsmessige og politiske konsekvensene. I denne artikkelen bruker vi to kausale design, endring-i-endringer og den syntetiske kontrollmetoden for å analysere effektene av nedbrenningen og tvangsevakueringen i Nord-Troms og Finnmark på politisk integrasjonen og deltakelse. Vi finner at nedbrenningen har hatt varige effekter på den politiske integrasjonen i Nord-Troms og Finnmark. Både valgdeltakelsen ved stortingsvalg og oppslutningen om Arbeiderpartiet faller mer i de nedbrente kommunene enn i andre nordnorske kommuner og i landet som helhet etter 1945. Vi observerer en kortsiktig nedgang i valgdeltakelse rett etter krigen, men den langsiktige negative effekten for Arbeiderpartiet kommer først til syne på 1970-tallet. Dette etterslepet kan forklares både med misnøye over håndteringen av krisen samt at nedbrenningen og sivilsamfunnets påfølgende traumer i liten grad ble inkludert i det kollektive minnet om Andre verdenskrig.publishedVersio

Oppslutningen om Ap, H, Sp og FrP ved sametingsvalg sammenliknet med stortingsvalg 1989–2017: Er det nasjonale valgvinder eller samepolitikken som teller?

Source at https://www.regjeringen.no/no/dokumenter/samiske-tall-forteller-11/id2626513/. Partisystemet i Sametinget kan betegnes som et hybrid system som består av både rene samiske lister som ikke stiller til valg til Stortinget, og nasjonale partier som stiller lister både til stortingsvalg og til sametingsvalg. Valgene til Sametinget og Stortinget holdes samtidig. Det er derfor interessant å finne ut om det i hovedsak er de nasjonale trendene i stortingsvalgene som bestemmer oppslutningen om de nasjonale partiene i sametingsvalgene, eller om oppslutningen til disse partiene i sametingsvalgene følger en egen logikk. Med utgangspunkt i teorier om såkalte første- og andreordensvalg, om sosial tyngdekraft samt effekter av valgordninger undersøker vi ved hjelp av valgdata omregnet til valgkretsene til Sametinget: 1) hvorvidt sametingsvalgene kan sies å være overskygget av stortingsvalgene for de nasjonale partiene Ap, H, Sp og FrP, 2) hvorvidt endringsmønstrene i oppslutningen mellom valgene varierer mellom de samiske kjerneområdene og områder der samisk kultur ikke er like synlig og 3) hvorvidt vi kan finne noen effekter av veksten i valgmanntallet og endringene i valgloven til Sametinget i 2009 på spørsmålene 1) og 2)

Dissecting the influence of Mg2+ on 3D architecture and ligand-binding of the guanine-sensing riboswitch aptamer domain

Long-range tertiary interactions determine the three-dimensional structure of a number of metabolite-binding riboswitch RNA elements and were found to be important for their regulatory function. For the guanine-sensing riboswitch of the Bacillus subtilis xpt-pbuX operon, our previous NMR-spectroscopic studies indicated pre-formation of long-range tertiary contacts in the ligand-free state of its aptamer domain. Loss of the structural pre-organization in a mutant of this RNA (G37A/C61U) resulted in the requirement of Mg2+ for ligand binding. Here, we investigate structural and stability aspects of the wild-type aptamer domain (Gsw) and the G37A/C61U-mutant (Gswloop) of the guanine-sensing riboswitch and their Mg2+-induced folding characteristics to dissect the role of long-range tertiary interactions, the link between pre-formation of structural elements and ligand-binding properties and the functional stability. Destabilization of the long-range interactions as a result of the introduced mutations for Gswloop or the increase in temperature for both Gsw and Gswloop involves pronounced alterations of the conformational ensemble characteristics of the ligand-free state of the riboswitch. The increased flexibility of the conformational ensemble can, however, be compensated by Mg2+. We propose that reduction of conformational dynamics in remote regions of the riboswitch aptamer domain is the minimal pre-requisite to pre-organize the core region for specific ligand binding

Front cover - Cell Membrane Wrapping: Influence of Cell Membrane Wrapping on the Cell−Porous Silicon Nanoparticle Interactions (Adv. Healthcare Mater. 17/2020)

Biohybrid nanosystems represent the cutting‐edge research in biofunctionalization of micro‐ and nano‐systems. Their physicochemical properties bring along advantages in the circulation time, camouflaging from the phagocytes, and novel antigens. This is partially a result of the qualitative differences in the protein corona, and the preferential targeting and uptake in homologous cells. However, the effect of the cell membrane on the cellular endocytosis mechanisms and time has not been fully evaluated yet. Here, the effect is assessed by quantitative flow cytometry analysis on the endocytosis of hydrophilic, negatively charged porous silicon nanoparticles and on their membrane‐coated counterparts, in the presence of chemical inhibitors of different uptake pathways. Principal component analysis is used to analyze all the data and extrapolate patterns to highlight the cell‐specific differences in the endocytosis mechanisms. Furthermore, the differences in the composition of static protein corona between naked and coated particles are investigated together with how these differences affect the interaction with human macrophages. Overall, the presence of the cell membrane only influences the speed and the entity of nanoparticles association with the cells, while there is no direct effect on the endocytosis pathways, composition of protein corona, or any reduction in macrophage‐mediated uptake