Statistical physics of biological systems


This line of research lies at the interface between statistical physics and biology. The challenge for anyone who positions themselves in this area of research is twofold. The first task is to develop models that are able to capture the intrinsically multi-scale character of biological processes, necessarily starting in a bottom-up fashion from capturing the important molecular aspects, in order to integrate them in a self-consistent way into more simplified models of cellular or even higher scale processes. The second challenge, perhaps the most fascinating one, is to probe the complexity of the experimental phenomenology of a given class of biological processes in order to determine the most general aspects while separating them from system-specific declinations. Interaction with fellow biologists and biotechnologists is of paramount importance in both cases.

More particularly, we are interested in the non-equilibrium aspects that characterise the dynamics of general biological processes such as:

  • Cell motility: migration and invasion processes in the context of tumour metastasis phenomena. Modelling of cellular signalling pathways associated with non-equilibrium locomotion processes such as chemotaxis (locomotion driven by liquid phase gradients) and durotaxis (locomotion driven by solid/viscoelastic phase gradients, such as stiffness gradients).

  • Diffusion and reaction processes in complex environments. The cell interior and inter-cellular phases in multicellular organisms are dense and structured environments, characterised by a myriad of non-equilibrium processes, which impose complex spatio-temporal correlations to thermal noise. The challenge is to study networks of chemical reactions occurring in environments where diffusive processes are profoundly modified by the interactions of biomolecules with the environment and where the detailed balance condition is broken by active processes involving driving and dissipation in reaction cycles.

People involved

Recent publications

Dass AV, Georgelin T, Westall F, Foucher F, De Los Rios P, Busiello DM, Liang S, Piazza F

Nature communications 12(1):1-0 (2021)

The exclusive presence of β-D-ribofuranose in nucleic acids is still a conundrum in prebiotic chemistry, given that pyranose species are substantially more stable at equilibrium. However, a precise characterisation of the relative furanose/pyranose fraction at temperatures higher

than about 50 °C is still lacking. Here, we employ a combination of NMR measurements and statistical mechanics modelling to predict a population inversion between furanose and pyranose at equilibrium at high temperatures. More importantly, we show that a steady temperature gradient may steer an open isomerisation network into a non-equilibrium steady state where furanose is boosted beyond the limits set by equilibrium thermodynamics. Moreover, we demonstrate that nonequilibrium selection of furanose is maximum at optimal dissipation, as gauged by the temperature gradient and energy barriers for isomerisation. The predicted optimum is compatible with temperature drops found in hydrothermal vents associated with extremely fresh lava flows on the seafloor.

Busiello DM, Liang S, Piazza F, De Los Rios P,, Liang S

Communications Chemistry 4(1):1-7 (2021)

Life has most likely originated as a consequence of processes taking place in non-equilibrium conditions (e.g. in the proximity of deep-sea thermal vents) selecting states of matter that would have been otherwise unfavorable at equilibrium. Here we present a simple chemical network in which the selection of states is driven by the thermodynamic necessity of dissipating heat as rapidly as possible in the presence of a thermal gradient: states participating to faster reactions contribute the most to the dissipation rate, and are the most populated ones in non-equilibrium steady-state conditions. Building upon these results, we show that, as the complexity of the chemical network increases, the velocity of the reaction path leading to a given state determines its selection, giving rise to non-trivial localization phenomena in state space. A byproduct of our studies is that, in the presence of a temperature gradient, thermophoresis-like behavior inevitably appears depending on the transport properties of each individual state, thus hinting at a possible microscopic explanation of this intriguing yet still not fully understood phenomenon.