Impact of A90P, F106L and H64V mutations on neuroglobin stability and ligand binding kinetics

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Shape Analysis - Applications to Medical Imaging

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Deep fluid transfer evidenced by surface deformation during the 2014–2015 unrest at Piton de la Fournaise volcano

International audienceIdentifying the onset of volcano unrest and providing an unequivocal identification of volcano reawakening remain challenging problems in volcanology. At Piton de la Fournaise, renewal of eruptive activity in 2014–2015, after 41 months of quiescence and deflation, was associated with long-term continuous edifice inflation measured by GNSS. Inflation started on June 9, 2014, and its rate progressively increased through 2015. Inflation onset was rapidly followed by an eruption on June 20–21, 2014, showing that volcano reactivation can be extremely fast, even after long non-eruptive phases. This short-lived eruption involved a shallow source (1.3–1.9 km depth below the summit). The inflation that followed, and eruptions in 2015, involved a larger depth range of fluid accumulation, constrained by inverse modeling at ca. 3.9 to 1.2–1.7 km depth. This time evolution reveals that volcano reawakening was associated with continuous pressurization of the shallowest parts of its plumbing system, triggered by progressive upwards transfer of magma from greater depth. A deep magma pulse occurred in mid-April 2015 and was associated with deep seismicity (3 to 9.5 km depth) and CO2 enrichment in fluids emitted by summit fumaroles. From this date, ground deformation accelerated and the output rates of eruptions increased, culminating in the long-lasting, large-volume, August–October eruption (~ 36 Mm3). This evolution suggests that deep magma/fluid transfer through an open conduit system first provoked the expulsion of the top of the plumbing system in June 2014, and then induced the progressive vertical transfer of the entire plumbing system down to 9 km (four eruptions in 2015). The new sustained feeding of the volcano was also at the origin of the hydrothermal system perturbation and the acceleration of the eastern flank motion, which favor lateral dike propagation and the occurrence of frequent and increasingly large eruptions. Our results highlight the fast and progressive way in which basaltic magmatic systems can wake up

Probing the Role of the Internal Disulfide Bond in Regulating Conformational Dynamics in Neuroglobin

In this report, we demonstrate that the internal disulfide bridge in human neuroglobin modulates structural changes associated with ligand photo-dissociation from the heme active site. This is evident from time-resolved photothermal studies of CO photo-dissociation, which reveal a 13.4± 0.9 mL mol−1 volume expansion upon ligand photo-release from human neuroglobin, whereas the CO dissociation from rat neuroglobin leads to a significantly smaller volume change (ΔV = 4.6 ± 0.3 mL mol−1). Reduction of the internal disulfide bond in human neuroglobin leads to conformational changes (reflected by ΔV) nearly identical to those observed for rat Ngb. Our data favor the hypothesis that the disulfide bond between Cys46 and Cys55 modulates the functioning of human neuroglobin

Investigating the deepest part of a volcano plumbing system: Evidence for an active magma path below the western flank of Piton de la Fournaise (La Réunion Island)

International audiencePeripheral diffuse degassing of CO2 from the soil occurs across the western flank of Piton de la Fournaise volcano (La Réunion Island, Indian Ocean) along a narrow zone. In this area, carbon isotopic analysis on soil gas samples highlights significant mixing between magmatic and organic end-members. The zones with the strongest mag- matic signature (highest δ13C) overlap spatial distribution of hypocenters recorded shortly before and during vol- cano reactivation and allow discriminating a N135° degassing lineament, with a minimum length of 11 km and 140 ± 20 m-width. Such orientation is in accordance with that of an old dyke network along the rift zone and with N120–130° and N140–155° lineaments related to the inheritance of oceanic lithosphere structures.Our findings show that this N135° lineament represents a preferential magmatic pathway for deep magma transfer below the volcano flank. Moreover, spatial distributions of recent eccentric cones indicate a well-founded possibil- ity that future eruptions may by-pass the shallow plumbing system of the central area of the volcano, taking a lat- eral pathway along this structure. Our results also confirm that Piton de la Fournaise activity is linked to a laterally shifted plumbing system and represent a major improvement in identifying the main high-risk area on the densely populated western flank of the volcano