Nanobiophysics

The organisation and dynamics of intracellular structures that maintain a cell’s form, shape, function and viability are rather complex. An emerging central theme which addresses this complexity deals with ATP-driven intracellular transport mechanisms along the tubulin network or the ability of mitochondria to rapidly undergo fission and fusion, and thereby creating a network that is adapted to the required ATP demands of the cell. In many physiological disorders, such as neuronal degeneration, these processes are disturbed, leading to increased cellular susceptibility to undergo cell death.

Physics modelling can add meaningful insight into the above processes. For example, semi-microscopic theories for membrane energetics and fluctuations can be utilised to understand the fusion between organelles. Descriptions including simple and driven – or active – dynamics of fusion and separation processes are possible. Predictions on transport processes and collective activity are accessible through nonequilibrium statistical physical treatments. On a slightly larger scale the insights from the fusion can be applied to network modalities. Here theoretical physical and mathematical characterisation of network properties would certainly assist in the analysis of experimental data.

For example the phenomena associated with autophagy can be studied through a variety of approaches.  We recently published a chapter “Autophagic Flux, Fusion Dynamics, and Cell Death” that shows how physics modelling can be added to the understanding of this process, understanding of which might ultimately help science to understand a variety of disorders.

The Nanobiophysics-SU group is particularly interested in the emerging field of organelle network analysis related to properties such as elasticity, connectivity and efficiency that report on molecular interactions and cellular function. A unique approach lies in the nested approach of theory and experimentally derived data on the nano-scale. By plugging into the power of molecular imaging technologies such as structured illumination superresolution microscopy (SR-SIM), this group addresses questions that arise only at the interface of nanotechnology and biology. SR-SIM allows to resolve specifically labelled structures down to 80 nm. Current projects address fusion dynamics between autophagosomes and lysosomes, mitochondrial network connectivity and actin-cyctoskeletal stiffness. For example, microscopy data together with physics models for networking and organelle structure can help to cast light on the dynamics inherent to mitochondrial networks numerically. The predictive power that this interdisciplinary approach allows to generate, is highly valuable for both biology and theoretical statistical physics alike.

The principal investigators are Dr Ben Loos (Dept of Physiological Sciences, Stellenbosch University) and Kristian Müller-Nedebock (Dept of Physics, Stellenbosch University)