Physics of Protein Machines; exploring harvesting light & making a molecular motor


Nanotechnology strives to construct the ultimate microscopic devices: machines on the nanometer scale that are spanned by as few as 10’s of atoms. If you get smaller than this, you cannot build it with atoms as we know them. Unsurprisingly, with over 4 billion years of evolution,
living systems have already discovered nanomachines at the lower size limit with performance beyond the wildest dreams of the nanotechnologist. These are the proteins: essentiallynanosolids built from robust, single polymer chains that can self-assemble into a unique, well-defined three-dimensional form. Understanding the physical principles that underpin protein structure and function is fundamental to modern molecular and cellular biology. It is also the key to the development of future nanotechnology. Two themes will be explored: light harvesting proteins and motor proteins. Light harvesting proteins couple light-active chromophores so as to harvest solar energy and transfer it to a photosystem that creates a charge separation and hence traps the energy. Do such systems use quantum mechanics, in particular, electronic coherence in a non-trivial way? Motor proteins are molecular machines that convert chemical energy into work in an environment where friction (thermal fluctuations) is dominant. How do they do it? One possibility is that motor proteins are a physical realisation of Maxwell’s demon. To test this, we are building a protein walker based on non-motor components that will move by rectifying noise. As per the demon, energy must be supplied, in this case via an input chemical potential.