Setsuro Ebashi (1922–2006)

a stroke six years ago in 2000. Thereafter, however, his health remained relatively stable, and during an international symposium in October 2005, celebrating the 40th anniversary of his discovery of troponin, he delivered a speech in English without a draft, as was his usual style, and impressed the scientists who were assembled from all over the world. His condition suddenly worsened a few days before his passing, which has been a deeply felt loss for his friends and pupils. After a relatively long time seeking to find his specialization, Ebashi decided to concentrate his research on the regulatory mechanism of muscular contraction in the early 1950s. By this time, he was already almost 30 years old and it seems to be a relatively late start in contrast to the subsequent rapid progress in his research. Prof. Ebashi first investigated the relaxing factor , which was the granular fraction extracted from skeletal muscles, and in 1957, he began to perceive a relationship between the relaxing factor and calcium ions. However, the laboratory was in poor condition after the war, not being equipped with either an ultracentrifuge or calcium isotope that was necessary to prove his hypothesis. Furthermore, when he obtained a series of chelating agents from Mr. Keihei Ueno, President of Dojindo Laboratories, and compared their calcium-binding activity with their muscle-relaxing activity he could not find any correlation. He was disappointed by these results and tentatively abandoned the idea of calcium being the key substance. When he decided to go abroad to study in Prof. Fritz Lipmann's laboratory of Rocke-feller Institute in 1959, he considered changing his research area. Prof. Lipmann, however, advised Ebashi to continue his research on the muscle. Around this period, Ebashi came across a paper in the library that suggested to him that the correlation between calcium-binding activity and muscle-relaxing activity of the chelating agents should be examined in the presence of magnesium ion. He then recalculated the relationship between the two activities and as a result found that they correlated exactly. This was an important turning point in his research career, and after that his research proceeded very smoothly. By fully utilizing an ultracentrifuge and calcium isotope, he discovered that the activity of the relaxing factor was due to the removal of calcium ion, and furthermore that an extremely low concentration of calcium ion directly acts on muscle proteins to induce a contrac-tile change. Upon returning …