Biology subjects

Roke, S.

Publications and source records attributed to Roke, S..

3 recordsLinked to original sources

bioRxiv2026

Fusion of lipid membranes: an alternative pathway

Membrane fusion is ubiquitous in myriad biological processes, including presynaptic neurotransmitter release, myoblast fusion, virus entry, and fertilization1-3. It is often considered in the presence of fusogenic proteins, which mediate the fusion by pulling the membranes into contact to overcome the high energy barrier imposed by hydration repulsion4-7. Here we uncover an alternative pathway - membrane fusion arising from electroporation induced by transmembrane potentials8,9 in absence of proteins. Using biased molecular dynamics simulations to carry out extensive potential-of-mean-force calculations10, we show how electroporation of opposing membranes promotes membrane fusion via formation of an intermembrane splayed lipid and peripore stalk, without any protein involvement. We validate our mechanism by demonstrating experimentally, via video microscopy and second harmonic generation imaging11 of interacting giant unilamellar vesicles (GUVs), that GUV fusion occurs in the presence of transmembrane potentials but not in their absence. The magnitude of these transmembrane potentials is biologically relevant, prevalent in transient states near the surfaces of cell membranes8,12, underscoring the potential importance of this mechanism in biological events.

biophysics↗

bioRxiv2024

Dissecting the membrane association mechanism of aerolysin pore at femtomolar concentrations using water as a probe

Aerolysin is a bacterial pore-forming toxin able to form transmembrane pores at the host plasma membrane of narrow internal diameter and great stability. These assets make it a highly promising nanopore for the detection of biopolymers such as nucleic acids and peptides. While much is known about aerolysin from a microbiological and structural side, its membrane association and pore-formation mechanism are not yet fully disclosed. Here, we studied the interaction of femtomolar concentrations of aerolysin and its mutants with liposomes in aqueous solution using angle-resolved second harmonic scattering (AR-SHS), in combination with single-channel current measurements. The measurements were so sensitive to detect electrostatic changes on the membrane-bound aerolysin induced by pH variation induced by the changes in the hydration shell of aerolysin. We reported for the first time the membrane binding affinity of aerolysin at different stages of the pore formation mechanism: while wt aerolysin has a binding affinity as high as 20 fM, the quasi-pore state and the prepore state show gradually decreasing membrane affinities, incomplete insertion and pore opening signature. Moreover, we quantitatively characterized the membrane affinity of mutants relevant for applications to nanopore sensing. This approach opens new possibilities to efficiently screen biological pores suitable for conducting molecular sensing and sequencing measurements, as well as to probe pore forming processes.

biophysics↗

bioRxiv2019

Biodegradable harmonophores for targeted high-resolution in vivo tumor imaging

Optical imaging probes have played a major role in detecting and monitoring of a variety of diseases1. In particular, nonlinear optical imaging probes, such as second harmonic generating (SHG) nanoprobes, hold great promise as clinical contrast agents, as they can be imaged with little background signal and unmatched long-term photostability2. As their chemical composition often includes transition metals, the use of inorganic SHG nanoprobes can raise long-term health concerns. Ideally, contrast agents for biomedical applications should be degraded in vivo without any long-term toxicological consequences to the organism. Here, we developed biodegradable harmonophores (bioharmonophores) that consist of polymer-encapsulated, self-assembling peptides that generate a strong SHG signal. When functionalized with tumor cell surface markers, these reporters can target single cancer cells with high detection sensitivity in zebrafish embryos in vivo. Thus, bioharmonophores will enable an innovative approach to cancer treatment using targeted high-resolution optical imaging for diagnostics and therapy.

bioengineering↗