Paul Ehrlich

Ehrlich and his co-workers made and tested a long series of arsenic compounds, and the 606th, arsphenamine, was made in 1907. After Sahachiro Hata showed in 1909 that it cured syphilis in infected rabbits, Ehrlich and Hata announced it on 19 April 1910 at the Congress for Internal Medicine in Wiesbaden, and Hoechst sold it as Salvarsan. Valent and colleagues describe it as the first synthetic agent against syphilis; it rested on Ehrlich's idea of a 'magic bullet' that would strike a parasite and spare the patient's own cells.

In 1897 Ehrlich proposed the side-chain theory: cells carry specific structures that bind a toxin, and when the cell makes more of them and releases them they act as antitoxin, or antibody. In 1900 he renamed these structures receptors. For his work on immunity he shared the 1908 Nobel Prize in Physiology or Medicine with Ilya Metchnikoff, whose theory of phagocytosis complemented his own.

From 1890 Ehrlich worked at Robert Koch's institute on Emil von Behring's diphtheria antitoxin. He showed that the antitoxin content of sera varied widely and defined units of antitoxin against a fixed standard, which the Nobel biography says became the basis of all later serum standardisation. From 1896 he directed the Prussian institute set up to control therapeutic sera, followed in 1899 by the Royal Institute of Experimental Therapy in Frankfurt.

As a student and young physician at the Charite in Berlin, Ehrlich sorted dyes into acid, basic and neutral kinds and used them to separate the granules in blood cells, work the Nobel biography says laid the foundations of haematology. In 1882 he published an improved stain for the tubercle bacillus that Koch had just identified, the basis of the later Ziehl-Neelsen method still in use.

In 1906 at the Georg-Speyer-Haus, Ehrlich told three chemists that atoxyl was not the 'anilide' of the accepted 1863 formula but an amino-phenylarsonic acid with a free amino group, and ordered the work to proceed on that basis. In Marquardt's account two of them, von Braun and Schmitz, refused and left; Bertheim stayed, and the joint paper with Ehrlich appeared on 1 May 1907. The Nobel biography credits Ehrlich with Bertheim for establishing the correct structural formula.

Insisting on his own chemical reading against the accepted formula, and ordering the work on that basis even when it cost him two chemists, is consistent with independent thinking; the same account shows the stance came at a price in staff. Independent Thinking

In 1909 Sahachiro Hata reported that compound 606, set aside in 1907 as ineffective, worked in syphilitic rabbits. Ehrlich asked him to repeat the experiments again and again, and by Marquardt's account Hata grew impatient before Ehrlich accepted the result and prepared the 1910 announcement; the Nobel biography says hundreds of experiments repeatedly proved its efficacy.

Asking for repeated confirmation of a result he badly wanted to be true is consistent with perfectionism; the same demand wore on the person doing the work. Perfectionism

In 1906 Ehrlich became director of the Georg-Speyer-Haus in Frankfurt, a chemotherapy research institute built beside his institute with money donated by Franziska Speyer. Its chemical laboratory let him move from serum work to making and testing compounds of his own design; Valent and colleagues call the donation an essential basis of the screening that led to 606.

Turning from serum work to a chemistry laboratory he did not have, and getting it through a private gift, is consistent with resourcefulness. Resourcefulness