Molecular machinery: quantifying the energetic cost of controlling nanoscale biological systems

At microscopic scales, biological systems must maintain a high degree of organization in order to properly function. Ultimately, this organization is achieved by the concerted efforts of a collection of nanoscale molecular machines: protein complexes that perform specific functions within the cell. Quantifying the flows of energy, information, and material through such systems is a central challenge in understanding their dynamics and in vivo operation. Currently, a number of important questions related to the function of molecular machines remain unanswered: what design principles produce efficient machines? What fundamental physical limitations are placed on these nonequilibrium systems? In this talk I will discuss our recent efforts to address some of these questions, making use of tools from nonequilibrium thermodynamics to quantify the energetic costs of driving strongly fluctuating systems. In particular, quantifying the dissipation associated with driving a fluctuating system between different states leads to conditions for efficient operation. Among other things, we find that there is an energetically optimal speed for systems to move at.