On day 135 of #LMB365 we have a 1970s drawing showing the hybrid atomic orbitals of the lysozyme system, to highlight Michael Levitt’s landmark paper on the theoretical studies of enzymic reactions, published on this day in 1976. This paper reported the first computerised model of an enzymatic reaction, a development that allowed any kind of chemical reaction to be simulated involving any kind of molecule, irrespective of size. For this work Michael shared the 2013 Nobel Prize in Chemistry. Reference: A. Warshel & M Levitt, Theoretical studies of enzymic reactions, Journal of Molecular Biology 103: 227-249.