[2][1] From 1952 to 1964, Hartley pioneered work on the sequence and mechanism of the enzyme chymotrypsin in Cambridge, and developed the use of paper chromatography to separate amino acids and peptides — an essential part of protein characterisation at that time.
[12][13][14] [15] [16] His group also showed that mammalian serine proteases, including the blood clotting cascade, had homologous structures and mechanisms, indicating a common evolutionary origin.
He left the Department of Biochemistry to set up Imperial's Centre for Biotechnology, and became a founding board member of Biogen – the longest surviving genetic engineering company.
Since then, Hartley has founded companies to make cheap bioethanol from waste hemicellulosic biomass, using genetically engineered compost heap microorganisms.
His comparative studies on other pancreatic proteolytic enzymes have revealed interesting homologies, which give information about the biological origin of the proteins and their mode of action.