Sir Hugh Stott Taylor (6 February 1890 – 17 April 1974) was an English chemist primarily interested in catalysis. In 1925, in a landmark contribution to catalytic theory, Taylor suggested that a catalysed chemical reaction is not catalysed over the entire solid surface of the catalyst but only at certain 'active sites' or centres. He also developed important methods for procuring heavy water during World War II and pioneered the use of stable isotopes in studying chemical reactions. Early life Taylor was born in St Helens, Lancashire, England in 1890, the son of glass technologist James and Ellen (née Stott) Taylor. He was educated at Cowley Grammar School in St Helens and then attended the University of Liverpool, where he received his BSc in 1909 and his MSc in 1910. Taylor then carried out three years of graduate work in Liverpool, after which he spent one year at the Nobel Institute in Stockholm in the laboratory of Svante Arrhenius and another at the Technische Hochschule in Hanover under Max Bodenstein. These studies earned him a PhD degree from the University of Liverpool in 1914. Basic research Taylor showed that chemisorption may be an activated process, and occur slowly. Moreover, he conceived the idea that chemically active sites might be sparse on the surface of a catalyst and, hence, could be inhibited with relatively few molecules. Taylor showed that hydrogen atoms are key intermediates of reactions involving H2 on metal surfaces and also discovered the conversion of heptane to toluene over chromium oxide. Protein structure Taylor and a graduate student developed the first semi-realistic model of the α-helix, an element of protein secondary structure. An earlier model by Astbury had been shown to be physically implausible by Hans Neurath. Using physical models and chemical reasoning, Taylor sought to find a better model, which differs only slightly from the modern α-helix proposed by Linus Pauling and Robert Corey. Taylor reported their models at his Franklin Medal lecture (1941) and in press (1942). Work at Princeton Taylor began at Princeton in 1914 as instructor in Physical Chemistry, and by 1915, was made an Assistant Professor. He was promoted to Professor of Physical Chemistry in 1922 and became chair of the Chemistry Department at Princeton in 1926, where he served until 1951. In 1927, Taylor became the David B. Jones Professor of Chemistry at Princeton. Taylor also served as the Dean of the Graduate