Real-time single-molecule monitoring and control of nanoparticle formation
Monitoring AuNP growth. Methods capable of controlling synthesis at the level of an individual nanoparticle are a key step towards improved reproducibility and scalability in engineering complex nanomaterials. To address this, we combine spatially-patterned activation of the photoreductant sodium pyruvate with interferometric scattering microscopy to achieve fast, label-free monitoring and control of hundreds of gold nanoparticles in real-time. Individual particle growth kinetics are well-described by two-step nucleation autocatalysis model, but with a distribution of individual rate constants that changes with reaction conditions.
Yize Wu joining us as a MRes student in Interdisciplinary Chemistry, Yize joins us to work on biohybrid nanopores.
Milan Singh Milan joins us as a MSci student this year, working on artificial cell self-replication.
Spatiotemporal stop-and-go dynamics of the mitochondrial TOM core complex correlates with channel activity
TOM diffusion is coupled to permeability. Here we show the correlation between lateral protein diffusion and channel activity of the general protein import pore of mitochondria (TOM-CC) in membranes resting on ultrathin hydrogel films. Using electrode-free optical recordings of ion flux, we find that TOM-CC switches reversibly between three states of ion permeability associated with protein diffusion. While freely diffusing TOM-CC molecules are predominantly in a high permeability state, non-mobile molecules are mostly in an intermediate or low permeability state. We explain this behavior by the mechanical binding of the two protruding Tom22 subunits to the hydrogel and a concomitant combinatorial opening and closing of the two β-barrel pores of TOM-CC. TOM-CC could thus represent a β-barrel membrane protein complex to exhibit membrane state-dependent mechanosensitive properties, mediated by its two Tom22 subunits.
Single-molecule FRET imaging of beta-barrel folding. In comparison to globular proteins, the spontaneous folding and insertion of β-barrel membrane proteins is surprisingly slow, typically occurring on the order of minutes. Using single-molecule Förster Resonance Energy Transfer to report on the folding of fluorescently-labelled Outer Membrane Protein G we measured the real-time insertion of a β-barrel membrane protein from an unfolded state. Folding events were rare, and fast (<20 ms); occurring immediately upon arrival at the membrane. This combination of infrequent, but rare, folding resolves this apparent dichotomy between slow ensemble kinetics, and the typical timescales of biomolecular folding.
Raj Paul Raj joins us as a Newton-Bhabha research internship as part of his PhD programme in IACS, India. He brings synthetic ion channels for single channel electrophysiology and single molecule imaging in Droplet Interface Bilayers.