Roger Y. Tsien (1952–2016)

Roger after the announcement of his winning of Nobel Chemistry Prize in 2008, credit of Erik Rodriguez. Roger Youchien Tsien, the founding pioneer of fluorescence imaging methods and Nobel Laureate in Chemistry in 2008, passed away on August 24. He was 64. Roger was born in New York City on February 1, 1952. His early life and professional career prior to his professorship at University of California, San Diego are vividly described in an autobiography at nobelprize.org (https://www. nobelprize.org/nobel_prizes/chemistry/ laureates/2008/tsien-bio.html). A talent for chemistry was evident from an early age, and he took full advantage of the encouragement—and occasional licensed reagent—from his father, an engineer, for increasingly complex and occasionally dangerous inorganic chemistry experiments in the basement and patio of their home in New Jersey. These youthful exploits included an ambitious, unsupervised multistep reaction sequence aimed at synthesizing aspirin. Looking back he said, ‘‘it was very good training in how to improvise equipment, plan and execute experiments, interpret confusing results, and decide how to do things better.’’ Eventually, Roger’s intellectual forays led him into the sparsely populated interface between major research fields, in which he decided to use the power of chemistry and optics to solve problems in biological visualization. This intrepid interdisciplinary spirit via technology development defined his work for the remainder of his career. Roger was known for pioneering the development of novel calcium imaging techniques during the 1980s, and his group created a few first-generation calcium indicators (quin-2, fura-2, indo-1, fluo-3, and others), their membranepermeable derivatives (acetoxymethyl [AM] ester forms) and caged calcium compounds. Using fura-2 and indo-1 as prototypes, he established methodologies for the quantitative measurement of intracellular calcium concentration based on ratiometric imaging. Moving beyond calcium, he worked alone or with colleagues to engineer and validate fluorescent indicators for cAMP, pH, and membrane voltage. Together, this multicolor toolbox for optical interrogation of molec-