Living systems, down to their smallest, truly living components — cells — are made up of a huge number of molecules. Resolving a cell molecule-by-molecule, namely at the level of chemistry and physics, is a long-held dream, as this feat would link the life sciences with the physical sciences at the most basic level. Can such a highly resolving microscopic view ever be realized? The answer seems to be yes, however, the respective microscope will take the form of a computer. Such computational microscope is already being developed, programmed to build on biological data, as well as on chemical and physical knowledge. When can we expect to look through such a microscope and see a cell in all its molecular detail? There is a good chance it will be around the year 2022, when the first ever exascale computer is supposed to become available. This computer will be a hundred times more powerful than today's leading machine. The optimism for soon resolving a whole cell with the computational microscope derives from a breakthrough project already achieved on present day computers, namely, the molecule-by-molecule view of a so-called cellular organelle, the photosynthetic chromatophore. This organelle is about 100 nm in size and, in volume, is about a hundredth of a very small living cell; exascale computing should enable accordingly the study of a whole, yet small, cell. The view of the chromatophore through the computational microscope, realized in full only this year, is amazing and beautiful. One sees a clockwork of linked, mostly rather elementary processes: light absorption producing optically excited chlorophyll molecules; chlorophyll excitation spreading through the entire chromatophore, inducing electron and proton transfer at certain centers; electrons being moved around by different charge carriers; protons being pumped into the chromatophores until the protons' pressure becomes high enough that they mechanically drive synthesis of molecules of ATP, a fuel that provides energy for most cellular activities. With the computational microscopy of the chromatophore, a major part of a biological cell has been resolved, for the first time in its entirety, at the level of truly basic chemistry and physics, showcasing how Angstrom-scale processes lead to 100-nm- scale overall function of solar energy harnessed to make ATP. Reaching the same detailed view for an entire living cell in 2022 promises an even better basic understanding of life in general, and human health in particular.
Argonne Physics Division Colloquium Schedule