Recent developments in synthetic biology may bring the bottom-up generation of a synthetic cell within reach. A key feature of a living synthetic cell is a functional cell cycle, in which DNA replication and segregation as well as cell growth and division are well integrated. Here, we describe different approaches to recreate these processes in a synthetic cell, based on natural systems and/or synthetic alternatives. Although some individual machineries have recently been established, their integration and control in a synthetic cell cycle remain to be addressed. In this Perspective, we discuss potential paths towards an integrated synthetic cell cycle.

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The magnetic tweezer is a single molecule manipulation instrument ideally suited to measuring biophysical systems at a constant applied force. The development of a magnetic tweezers with a high-speed camera and GPU-accelerated particle tracking has allowed for the measurement of molecular events at the millisecond time scale. However, as the spatial resolution of the instrument is improved, previously neglected sources of noise start to become limiting, such as: mechanical stability of the sample stage, and coherent light artifacts such as speckle. Here, we isolate the various sources of noise in an attempt to determine the fundamental limit to magnetic tweezer resolution. We use a state-of-the-art high spatial and temporal resolution magnetic tweezer to measure the dynamics of model systems such as DNA hairpins.

The classical Oseen-Frank theory of liquid crystal elasticity is based on the experimentally verified fact that there are three independent modes of distortion, each with its associated elastic constant. On the other hand the arguably more first-principles order parameter-based Landau-de Gennes theory only involves two independent elastic modes. The resulting "elastic constants problem" has led to a considerable amount of vexation among theorists. In a series of papers at the turn of the century Fukuda and Yokoyama suggested that the resolution of this problem could be found in the proper treatment of non-local effects in the ideal part of the free energy. They used an ingenious, but technically complex, technique based on a fieldtheoretic approach to semi-flexible polymers. Here we revisit their idea but now in the more accessible framework of density functional theory of rigid particles. Our work recovers their main results for rod-like particles, in that generically an ordered assembly of non-interacting rods has three independent elastic constants associated to it that all scale as the square of the length of the particles and obey the inequalities K2 < K1 < K3. We also consider the case of disk-like particles, and then find in line with expectations that K3 < K1 < K2.