Promotionsvortrag Physik: „Phenomenological Perspectives in Biophysics“

Ankündigung des Promotionsvortrags von: Herrn Conrad Möckel

In this thesis defense, I present non-invasive, label-free optical approaches for quantifying biolog-ical material properties across subcellular length scales. A central focus lies on mass density, which links molecular composition to mechanical behavior and transport phenomena, yet is rarely measured directly. Simple mixture models relate refractive index measurements to local mass density, but the accuracy, especially in complex biological matter, is often limited by incomplete knowledge of the molecular composition. I show how this uncertainty propagates and why it moti-vates direct density measurements. Stimulated Brillouin scattering provides such a direct readout by exploiting photon-phonon interactions. I demonstrate its applicability to biological matter and discuss how it can serve as a quantitative benchmark for refractive-index-based estimates, broad-ening the scope of density-based inferences in biological studies. In the second half of the talk, I discuss bright-field differential dynamic microscopy (DDM). By analyzing inherent density fluctua-tions in microscopy movies without the presence of exogenous labels or tracer particles, DDM yields the intermediate scattering function across length and time scales. In Xenopus laevis egg extract as a model system for cytoplasm, I show how DDM reveals viscoelastic subdiffusion and non-Gaussian displacement statistics. Perturbations of biochemical activity and cytoskeletal or-ganization modulate these dynamics and motivate the notion of hierarchical heterogeneities in the cytoplasm. I close by outlining next steps and future directions.

(Vortrag auf Englisch)

Dem Vortrag schließt sich eine Diskussion von 15 Minuten an. Vortrag und Diskussion sind öffentlich. Diesen Verfahrensteilen folgt ein nicht öffentliches Rigorosum von 45 Minuten.