 She had worked with Dorothy Crowfoot Hodgkin to solve the x-ray crystal structure of penicillin, and was later active in protein crystallography.The phase problem had not yet been solved to allow determination of protein structure, so his Ph.D. thesis (completed in 1952) studied the density and solvent content in crystals to help determine very accurate molecular weights for proteins.In 1954 he went to the Carlsberg Laboratory in Copenhagen to do postdoctoral research with Kaj Linderstrøm-Lang, where he started his classic work on the ribonuclease enzyme.