Biophysical Society Thematic Meeting | Ascona, Switzerland

Liposomes, Exosomes, and Virosomes: From Modeling Complex Membrane Processes to Medical Diagnostics and Drug Delivery

Monday Speaker Abstracts

Fluorescence-free Imaging and Tracking of Individual Secretory and Transmembrane Proteins in a Living Cell Matthew P. McDonald , Katharina König, André Gemeinhardt, Richard W. Taylor, Susann Spindler, Vahid Sandoghdar. Max Planck Institute for the Science of Light, Erlangen, Bavaria, Germany. The cellular membrane plays a pivotal role in many biological and medical processes. As an example, proteins protruding from the membrane serve as signaling centers to nearby cells and extracellular biomolecules. Intercellular communications and secretions are also mediated by the membrane through endosome-membrane fusion. Here, we present our recent efforts towards understanding this ubiquitous dynamic system. Using a novel optical interferometric scattering detection technique (iSCAT), we observe real-time secretion events of single label-free proteins ejected from a living cell. Importantly, iSCAT functions by way of mixing the weak analyte’s scattering signature with a relatively strong reflected plane wave. Even the tiniest nanoparticles are, therefore, observed via the interference between these two signals. In addition, we perform analogous measurements to track gold nanoparticle labeled transmembrane proteins and lipids in three dimensions as they diffuse across living cells and giant unilamellar vesicles. Temporal and spatial resolutions of ~50 µs and ~1 nm are routinely achieved, allowing for an unprecedented look into membrane-protein diffusion dynamics. The developed method thus has the potential to solve a wide range of problems in cellular physiology, such as intercellular signaling, immunology, and cancer malignancy.

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