Biology subjects

Paracini, N.

Publications and source records attributed to Paracini, N..

4 recordsLinked to original sources

bioRxiv2025

Myelin Basic Protein Binding Is Modulated by Leaflet Asymmetry and Lipid Composition

Compositional asymmetry between lipid bilayer leaflets is a defining feature of biological membranes, yet its role in modulating protein binding remains largely unexplored. Here, we investigate how leaflet-specific composition affects the interaction between Myelin Basic Protein and biomimetic myelin membranes using neutron reflectometry. Asymmetric supported myelin bilayers containing deuterated cholesterol in the cytoplasmic leaflet enabled resolution of structural asymmetry. Neutron reflectometry measurements show that Myelin Basic Protein binds preferentially to asymmetric supported bilayers mimicking native myelin, whereas Experimental Autoimmune Encephalomyelitis-modified compositions exhibit weaker binding and more pronounced protein insertion. Disruption of asymmetry--either by thermal-induced lipid redistribution or by using symmetric cytoplasmic myelin--leads to a marked reduction in Myelin Basic Protein binding, despite increased membrane charge. Following vesicle adsorption and formation of a second bilayer, the protein layer narrows to near in vivo thickness in both systems, with the diseased condition exhibiting a wider inter-bilayer spacing. These results underscore the relevance of lipid asymmetry and composition in governing protein - membrane interactions, with implications for the molecular basis of myelin stability and demyelination.

biophysics↗

bioRxiv2025

Glycation enhances protein association with lipid bilayer membranes

Glycation is a non-enzymatic post-translational modification that leads to the formation of advanced glycation end-products (AGEs), which accumulate in the blood-stream under chronic hyperglycemia and are implicated in diabetes-related pathologies. While glycated proteins such as albumin or hemoglobin are widely used as biomarkers for glycemic control, the structural and chemical changes induced by glycation may also alter their interactions with lipid interfaces, including cellular membranes and lipoproteins, potentially affecting their biological distribution and diagnostic detectability. In this study, we investigated how glycation influences the interaction of bovine serum albumin (BSA) with supported lipid bilayers (SLBs) of different compositions, used as model systems to replicate the diversity of membrane surface charges and fluidity. Using neutron reflectometry (NR), we compared the membrane association of BSA and a chemically-enhanced glycated form of BSA (gBSA), focusing on nanostructural changes at the bilayer interface. Our results showed negligible interaction of either proteins with zwitterionic or cationic membranes. In contrast, both BSA and gBSA exhibited significant binding to negatively charged bilayers, with glycation significantly amplifying this interaction. Quantitatively, the membrane-associated protein volume fraction increased from 0.11 (BSA) to 0.17 (gBSA), suggesting that glycation modifies the proteins surface properties in ways that promote stronger lipid interactions with negatively charged membranes. These findings suggest that glycation not only affects protein structure but also modulates protein-membrane affinity in a lipid-dependent manner. This has important implications for the bioavailability and behavior of glycated albumin in the bloodstream, potentially influencing the accuracy of clinical assays and contributing to membrane-related pathophysiology in diabetes. Our work highlights the need for a deeper understanding of glycation-induced changes in protein-lipid interactions and their consequences for biomarker reliability and disease mechanisms. Graphical TOC Entry O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=82 SRC="FIGDIR/small/685514v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@150e71aorg.highwire.dtl.DTLVardef@749b35org.highwire.dtl.DTLVardef@179f468org.highwire.dtl.DTLVardef@19cfe8e_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2025

Bcl-2 Oligomerizes Bax on the Mitochondrial Membrane Surface Preventing the Initial Stages of Apoptosis

The Bcl-2 family of proteins control mitochondrial outer membrane (MOM) pore formation, crucial to cellular clearance via apoptosis. However, the molecular principles by which opposing family members inhibit, mediate or promote MOM perforation remain elusive. Here, we demonstrate that cell-protecting Bcl-2 directly sequesters cell-killing Bax into a protein-protein complex at the membrane interface preventing Bax forming apoptotic pores. Neutron reflectometry showed Bax association with Bcl-2 occurs through the formation of Bax protein oligomers on the membrane surface. Bax binding to the membrane surface was proportional to the membrane-embedded Bcl-2 suggestive of protein-protein complex formation through both Bcl-2/Bax and Bax/Bax interactions. Bcl-2/Bax sequestration to prevent perforation was observed in membrane models with and without pro-apoptotic cardiolipin present. Our findings shed fundamental new light on the communication of Bcl-2 with its cell-killing relatives at the mitochondrias membraneous exterior to prevent cells from undergoing apoptosis. TeaserMembrane-embedded Bcl-2 sequesters Bax, to prevent the perforation of mitochondrial membranes by Bax which would initiate apoptosis.

biophysics↗

bioRxiv2022

Structural Characterisation of Nanoparticle-Supported Lipid Bilayers by Grazing Incidence X-ray and Neutron Scattering

The structure of supported lipid bilayers formed on a monolayer of nanoparticles was determined using a combination of grazing incidence X-ray and neutron scattering techniques. Ordered nanoparticle arrays assembled on a silicon crystal using a Langmuir-Schaefer deposition were shown to be suitable and stable substrates for the formation of curved and fluid lipid bilayers that retained lateral mobility, as shown by fluorescence recovery after photobleaching. A comparison between the structure of the curved bilayer assembled around the nanoparticles with the planar lipid membrane formed on the flat underlying silicon oxide surface revealed a [~]5 [A] thinner bilayer on the curved interface, resolving the effects of curvature on the lipid packing and overall bilayer structure. The combination of neutron scattering techniques, which grant access to sub-nanometre scale structural information at buried interfaces, and nanoparticle-supported lipid bilayers, offers a novel approach to investigate the effects of membrane curvature on lipid bilayers.

biophysics↗