368 research outputs found
Editorial: Physical Virology and the Nature of Virus Infections
Full text linkVirus particles, 'virions', range in size from nano-scale to micro-scale. They have many different shapes and are composed of proteins, sugars, nucleic acids, lipids, water and solutes. Virions are autonomous entities and affect all forms of life in a parasitic relationship. They infect prokaryotic and eukaryotic cells. The physical properties of virions are tuned to the way they interact with cells. When virions interact with cells, they gain huge complexity and give rise to an infected cell, also known as 'virus'. Virion-cell interactions entail the processes of entry, replication and assembly, as well as egress from the infected cell. Collectively, these steps can result in progeny virions, which is a productive infection, or in silencing of the virus, an abortive or latent infection. This book explores facets of the physical nature of virions and viruses and the impact of mechanical properties on infection processes at the cellular and subcellular levels.
Keywords: Acidic pH; Active matter; Alkaline pH; Anisotropic mechanics; Cell biology; Computational virology; Genome release; Inclusion bodies; Liquid unmixing; Maturation; Mechanical properties; Modelling; Physics; Pressure; Proton diode; Reverse transcription; Stiffness; Structural evolution; Tracking; Trafficking; Uncoating; Viral lineage; Virion; Virion morphogenesis; Virus; Water wir
Fluorescence Tracking of Genome Release during the Mechanical Unpacking of Single Viruses
Full text linkViruses package their genome in a robust protein coat to protect it during transmission between cells and organisms. In a reaction termed uncoating, the virus is progressively weakened during entry into cells. At the end of the uncoating process the genome separates, becomes transcriptionally active, and initiates the production of progeny. Here, we triggered the disruption of single human adenovirus capsids with atomic force microscopy, and followed genome exposure by single molecule fluorescence microscopy. This method allowed the comparison of immature (non-infectious) and mature (infectious) adenovirus particles. We observed two condensation states of the fluorescently labeled genome, a feature of the virus that may be related to infectivity. Beyond tracking the unpacking of virus genomes this approach may find application in testing the cargo release of bio-inspired delivery vehicles
Zircon petrochronology reveals the timescale and mechanism of anatectic magma formation
Full text linkIgneous rocks of intermediate to acidic composition commonly exhibit considerable degrees of isotope variability preserved at the crystal and sub-crystal scale, as well as a significant U–Pb age range, reflecting protracted timescales of zircon crystallization and long magma residence times. The association of high-precision U–Pb zircon dates with stable and radiogenic isotope data represents a powerful tool to unravel the petrological evolution of granitic rocks, hence allowing a better understanding of the processes that led to the formation and reworking of the continental crust. In this case study, we combine high-precision U–Pb dates with stable and radiogenic isotope data from zircon crystals in the Larderello–Travale (Italy) shallow-level granites. These rocks are peraluminous two-mica, cordierite-bearing granites and represent pure crustal anatectic magmas, generated in a post-collisional extensional setting. As such, they are ideal candidates to investigate the timing, rates and mechanisms of melt production during anatectic magma formation, giving insights into the process of intracrustal differentiation. Magmatic zircon crystals from the Larderello–Travale granites contain δ18O values ranging from 8.6 to 13.5‰ and crystals from individual samples exhibit inter- and intra-grain oxygen isotope variability exceeding 3‰. The analysed crystals have εHf values ranging between −7.4 and −12.4, with moderate, intra-sample εHf isotope variability. All CA-ID-TIMS (chemical abration isotope-dilution thermal ionization mass spectrometry) 206Pb/238U zircon ages range from 4.5 to 1.6 Ma and suggest four pulses of magmatic activity at ∼3.6, 3.2, 2.7 and 1.6 Ma. More importantly, zircon crystals from individual samples typically exhibit an age spread as large as 300–500 ka. This age dispersion suggests that most of the zircon did not crystallize at the emplacement level but in the middle crust and were subsequently recycled and juxtaposed during ascent and emplaced at shallow level. When plotted against age, stable and radiogenic isotope data suggest the co-existence of multiple and isotopically distinct magma batches produced by partial melting of different crustal domains. This requires coeval magma batches that are physically separated and evolve independently for hundreds of thousands of years before coalescing during ascent and emplacement. The involvement of multiple sources in the production of crustal anatectic magmas reflects the inherent heterogeneous nature of the continental crust and result from the interplay between the rise and evolution of the geotherms through the crust and the composition of the fertile source rocks. Finally, the isotopically diverse zircon-bearing magma batches mixed and assembled into shallow-level intrusions generated during the four major magma pulses
A novel gene therapy approach for the treatment of tumours with microsatellite instability
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Experimental dissolution of molybdenum-sulphides at low oxygen concentrations: A first-order approximation of late Archean atmospheric conditions
Full text linkThe abundance of atmospheric oxygen and its evolution through Earth's history is a highly debated topic. The earliest change of the Mo concentration and isotope composition of marine sediments are interpreted to be linked to the onset of the accumulation of free O2 in Earth's atmosphere. The O2 concentration needed to dissolve significant amounts of Mo in water is not yet quantified, however. We present laboratory experiments on pulverized and surface-cleaned molybdenite (MoS2) and a hydrothermal breccia enriched in Mo-bearing sulphides using a glove box setup. Duration of an experiment was 14 days, and first signs of oxidation and subsequent dissolution of Mo compounds start to occur above an atmospheric oxygen concentration of 72 ± 20 ppmv (i.e., 2.6 to 4.6 × 10−4 present atmospheric level (PAL)). This experimentally determined value coincides with published model calculations supporting atmospheric O2 concentrations between 1 × 10−5 to 3 × 10−4 PAL prior to the Great Oxidation Event and sets an upper limit to the molecular oxygen needed to trigger Mo accumulation and Mo isotope variations recorded in sediments. In combination with the published Mo isotope composition of the rock record, this result implies an atmospheric oxygen concentration prior to 2.76 Ga of below 72 ± 20 ppmv
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