ROGER YONCHIEN TSIEN 1February1952— 24August2016 ElectedForMemRS 2006 By ChristopherL.-H.HuangDM(Oxford), ScD(Cambridge), FESC* PhysiologicalLaboratoryandDepartmentofBiochemistry,Universityof Cambridge,DowningStreet,CambridgeCB23EG,UK RogerYonchienTsiendisplayedprecociouschildhoodtalentsinchemistry.Aftergraduating from Harvard University in chemistry and physics in 1972, he pursued a PhD programme in the Physiological Laboratory, Cambridge, under the supervison of Professor Richard Adrian (FRS 1977) with Marshal Scholarship support. His thesis ‘The design and use of organic chemical tools in cellular physiology’ won the Gedge Prize and a Comyns Berkeley Research Fellowship by Gonville and Caius College, supporting his postdoctoral + + workdevelopingCa2 -sensitiveelectrodesandﬂuorescentprobesmeasuringcellular[Ca2 ].
408 BiographicalMemoirs Earlydaysand education RogerYonchienTsienwasborninNewYorkCityon1February1952,thethirdofthreesons to MIT-trained mechanical engineer Hsue Chu Tsien and trained nurse Yi Ying. His family lineage fell within the scholar-gentry Hangzhou tradition, with early historically recorded interactions with the Song Dynasty. His family background also had an unusual backdrop reﬂectingtheChinesehistoricaleventsduringandimmediatelyfollowingtheSecondWorld War.Theiroftenexceptionallytalentedprogenyoftenledimpressiveandimaginativecareers intheWestdespiteadversityandevenprejudice.
RogerYonchienTsien 409 a chance to develop their original drive and independence than amassing a collection of subordinatestoilinguncriticallyunderthedirectionofaprincipalinvestigator.Suchwasalso the culture in the Physiological Laboratory (Hill 1965), which doubtless contributed to its distinguishedscientiﬁchistory,includingNobelprizesincellularphysiologybeginningfrom E.D.AdrianFRSandA.V.HillFRS.
410 BiographicalMemoirs of a Comyns Berkeley Research Fellowship by Gonville and Caius College. Elections to such college research fellowships are highly competitive, with independent scrutiny of the candidates’ submitted works by distinguished outside assessors, and provide support for a free choice of research activities in Cambridge over a ﬁve-year period, ideal for someone of Roger’s independence and originality. This period likely established the foundations for Roger’s scientiﬁc life. He began his developments of chemical and, later, molecular biological probes that could be introduced into, or expressed, in the cell interior for studies of its physiological processes. This highly individualistic and elegant pursuit by + someone extraordinarily gifted in organic chemistry initially focused on intracellular Ca2 measurements, although later studies were inclusive of a wide range of further ions and molecules.Thisinitialinterestwastimely:overthe1970sitbecameappreciatedthatcytosolic + [Ca2 ] was a key central second messenger. Clariﬁcation of its modiﬁcation following a triggeringactivationorregulatorystep,andmodulationofthisprocessbyexchangesbetween + freeandboundcytosoliccompartments,intracellularCa2 storesandtheextracellularspace, wascentraltounderstandingtheregulationofcellularactivity.
RogerYonchienTsien 411 (a) (c) (b) + Figure1.DevelopmentanduseofCa2 -sensitiveelectrodes.(a)Potentialdifference,E + developed + + Ca2 acrossCa2 -selectivemembranerelativetoreferencepotentialV asaresultofCa2 activitiesinthe 0 sampledﬂuid,a ,andwithintheelectrode,a.(b)Microelectrodemeasurementconﬁgurationtomeasure + s f Ca2 activity in an excitable cell with membrane potential E , comparing the potentials generated + m by the tetraphenylphosphonium oxonol Ca2 sensor microelectrode and voltage-sensitive electrode + impalementsE andE respectively.(c)Expectedcalibrationplots:thetheoreticalNernstplotforCa2 1 2 inwhichapCaof3isassignedzerovoltage.
412 BiographicalMemoirs + methods to this end. Optical methods show better Na rejection and faster responses in contrast to the slow response times of electrode methods, suitable for monitoring biological events. In contrast to monitoring conditions at a point, optical methods also + provided [Ca2 ] estimates averaged over deﬁned regions of interest and could also + characterizespatial[Ca2 ]distributionwiththesubsequentlyavailableconfocalmicroscopic techniques.
RogerYonchienTsien 413 (a) (b) (c) (d) (e) + Figure 2. Ca2 -chelating compounds leading to development of quin-2. (a) EGTA, illustrating cage formedbythefourcarboxylgroups.Thisgeometryisconservedin(b),theanalogueBAPTA,despite + replacementsofthemethylenegroups.(c)Theacetomethoxy(AM)esterofthesimilarlyCa2 -binding indicatorquin-2readilypermeatescellmembraneswhereendogenousesterasescleavetheestergroups, + yielding(d)quin-2,whoseﬂuorescenceincreasessixfoldwithincreased[Ca2 ].
414 BiographicalMemoirs Finally, cell incubation in solutions containing the membrane-permeant acetomethoxy (AM) ester quin-2-AM accomplished atraumatic yet consistent intracellular access without micromanipulation or plasma membrane disruption. Endogenous esterases then split off the ester groups releasing and trapping the membrane-impermeant quin-2 tetra-anion (7) + (ﬁgure 2d). Increases in quin-2 ﬂuorescence with increased [Ca2 ] could be monitored by conventional cuvette spectroﬂuorimeter. Quin-2 thus became strategic in cytosolic + [Ca2 ] measurements in a wide range of mammalian cells and cell suspensions, including lymphocytes, thrombocytes, spermatozoa, neutrophils and macrophages, particularly in + assessments of the roles of Ca2 in stimulus–response coupling (8, 9). In future years this approachtocellularintroductionofesteriﬁedmembrane-permeant derivativeswasextended to studies of the roles of candidate cell messenger molecules, such as phosphatidylinositol 3,4,5-trisphosphate,incellphysiology(25).