Kenneth Charles Holmes. 19 November 1934—2 November 2021

Kenneth Holmes catalysed the transformation of ‘protein crystallography’ into ‘structural biology’. His demonstration in 1970, with his student Gerd Rosenbaum, and with the collaboration of Jean Witz from Strasbourg, that synchrotron radiation could be a suitable X- ray source for biological diffraction experiments opened vast new possibilities for visualizing the molecules of life. Holmes’ move from Cambridge to Heidelberg in 1968, which enabled the landmark 1970 experiment at the Deutsches Elektronen-Synchrotron in Hamburg, was a critical event in bringing structural biology to continental Europe—a science born in England and for which Cambridge continued at that time to be the locus of its most important innovations. Holmes’ own analysis of the molecular mechanism of muscle contraction exemplified the power of this new technology and the importance of visualizing the atomic structures of dynamic molecular assemblies.