Biology subjects

Bohic, S.

Publications and source records attributed to Bohic, S..

5 recordsLinked to original sources

bioRxiv2025

A hierarchical nickel organic framework confers high conductivity over long distances in cable bacteria

Multi-cellular cable bacteria have evolved a unique machinery that efficiently transports electrons across centimetre-scale distances. Currents flow through a parallel network of periplasmic fibres, which display an extraordinary conductivity for a biological material. However, the conduction mechanism remains elusive as the molecular structure of the fibres has not been resolved. Here, we demonstrate that each fibre embeds a bundle of intertwined nanoribbons, which are built from Nickel Bis(Dithiolene) (NiBiD) repeat units that are formed by linking nickel centres with ethenetetrathiolate ligands. The planar and conjugated NiBiD complexes are aligned and stacked to form an elongated supramolecular coordination network, thus explaining the observed organo-metal electronic properties of the fibres. Our results hence demonstrate that biology is capable of producing extensive metal organic frameworks. These structures enable highly conductive one-dimensional conduits, ensuring efficient charge transport over macroscale distances, thus providing a novel design principle for bio-based, sustainable organo-electronic materials.

molecular biology↗

bioRxiv2025

Cryo-Correlative Light and X-ray microscopies: Expanding the Intracellular Chemical Map

We introduce a powerful, integrated workflow that fuses cryo-optical fluorescence microscopy with cryogenic synchrotron radiation X-ray fluorescence nanoimaging to unlock unprecedented nanoscale insights into cellular ultrastructure and composition. Our method delivers sharp 2D and 3D visualizations enabling simultaneous elemental mapping, nanoparticle tracking, and imaging of mitochondrial features via a luminescent cyclometalated iridium complex. We further demonstrated that combining well-chosen molecular probes possessing different heavy elements (e.g. rhenium, iridium, bromine and iodine) allows elemental multiplex "painting" of different organelle to provide X-ray fluorescent elemental contrast of some intracellular structure. By eliminating the need for separate sample preparations, this streamlined approach maximizes limited synchrotron beamtime and dramatically accelerates data acquisition, setting a new benchmark for advanced cryo-nanoscale imaging studies.

cell biology↗

bioRxiv2023

Identification of the Intracellular Protein Targets of a Bio-active Clickable Half-Sandwich Iridium Complex by Chemical Proteomics

Identification of intracellular targets of anticancer drug candidates provides key information on their mechanism of action. Exploiting the ability of the anticancer (C^N)-chelated half-sandwich iridium(III) complexes to covalently bind proteins, click chemistry with a bioorthogonal azido probe was used to localize a phenyloxazoline-chelated iridium complex within cells and profile its interactome at the proteome-wide scale. Proteins involved in protein folding and actin cytoskeleton regulation were identified as high affinity targets. Upon iridium complex treatment, HSP90 folding activity was inhibited in vitro and major cytoskeleton disorganization was observed. We used a wide array of imaging and biochemical methods to validate selected targets and obtain a multiscale overview of the effects of this complex on live human cells. We demonstrate that it behaves as a dual agent, inducing both electrophilic and oxidative stresses in cells that account for its cytotoxicity.

biochemistry↗

bioRxiv2022

Virtual histology of Alzheimer's Disease: why are amyloid-β plaques visible with X-ray phase-contrast imaging?

Amyloid-{beta} (A{beta}) plaques from Alzheimers Disease (AD) can be visualized ex vivo in label-free brain samples using synchrotron X-ray phase-contrast tomography (XPCT). However, for XPCT to be useful as a screening method for amyloid pathology, it is essential to understand which factors drive the detection of A{beta} plaques. The current study was designed to test the hypothesis that A{beta}-related contrast in XPCT could be caused by the A{beta} fibrils and/or by metals trapped in the plaques. This study probed the fibrillar and elemental compositions of A{beta} plaques in brain samples from different types of AD patients and AD models to establish a relationship between XPCT contrast and A{beta} plaque characteristics. XPCT, micro-Fourier-Transform Infrared spectroscopy and micro-X-Ray Fluorescence spectroscopy were conducted on human samples (genetic and sporadic cases) and on four transgenic rodent strains (mouse: APPPS1, ArcA{beta}, J20; rat: TgF344). A{beta} plaques from the genetic AD patient were visible using XPCT, and had higher {beta}-sheet content and higher metal levels than the sporadic AD patient, which remained undetected by XPCT. A{beta} plaques in J20 mice and TgF344 rats appeared hyperintense on XPCT images, while they were hypointense with an hyperintense core in the case of APPPS1 and ArcA{beta} mice. In all four transgenic strains, {beta}-sheet content was similar, while metal levels were highly variable: J20 (zinc and iron) and TgF344 (copper) strains showed greater metal accumulation than APPPS1 and ArcA{beta} mice. Hence, a positive contrast formation of A{beta} plaques in XPCT images appeared driven by biometal entrapment. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=143 SRC="FIGDIR/small/509706v2_ufig1.gif" ALT="Figure 1"> View larger version (48K): org.highwire.dtl.DTLVardef@56e672org.highwire.dtl.DTLVardef@1336d85org.highwire.dtl.DTLVardef@15b6690org.highwire.dtl.DTLVardef@1aaa6cb_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIAmyloid-{beta} plaques in the different forms of Alzheimers Disease have various contrasts in X-ray phase-contrast tomography C_LIO_LIIn transgenic rodents, a core-restricted, positive contrast is driven by the level of metal entrapment within plaques C_LIO_LIIn humans, greater and more diffuse metal accumulation lead to a positive contrast in a genetic case of AD C_LI

biophysics↗

bioRxiv2019

Identification of distinct pathological signatures induced by patient-derived α-synuclein structures in non-human primates

AO_SCPLOWBSTRACTC_SCPLOWDopaminergic neuronal cell death, associated with intracellular -synuclein (-syn)-rich protein aggregates (termed Lewy bodies), is a well-established characteristic of Parkinsons disease. Much evidence, accumulated from multiple experimental models has suggested that -syn plays a role in PD pathogenesis, not only as a trigger of pathology but also as a mediator of disease progression through pathological spreading. Here we have used a machine learning-based approach to identify unique signatures of neurodegeneration in monkeys induced by distinct -syn pathogenic structures derived from PD patients. Unexpectedly, our results show that, in non-human primates, a small amount of singular -syn aggregates is as toxic as larger amyloid fibrils present in the LBs, thus reinforcing the need for preclinical research in this species. Furthermore, our results provide evidence supporting the true multifactorial nature of PD as multiple causes can induce similar outcome regarding dopaminergic neurodegeneration.

neuroscience↗