US biochemist who, with Japanese organic chemist and marine biologist Osamu Shimomura and US geneticist Martin Chalfie, shared the Nobel Prize for Chemistry in 2008 for his contributions to the discovery and development of the Green Fluorescent Protein (GFP).
Tsien's studies centred on understanding the mechanism of how GFP glows. He showed that bacteria transformed with the GFP gene only fluoresce when grown in the presence of oxygen. Tsien concluded from his observations that the GPD catalyses a chemical transformation which modifies a few of its own amino acids to create a light-producing structural element or chromophore. Tsien and his coworkers also studied the red fluorescent protein (DsRed) from the coral Discosoma, and combining some of its characteristics with those of GFP to produce a GPD variant that glowed red instead of green, thus showing that the colour palette of GPD could be extended. Tsien's group also produced GFP variants with improved brightness and folding characteristics and helped determine the crystal structure of the GFP. This work helped in the understanding of the basic scientific principles which make GFP produce light, and also added to its usefulness, as the multiple colour variants now allow researchers to follow the activity of several genes at the same time. GFP and its variants are now available commercially as a molecular biology kit, and have proven extremely useful in many fields of life sciences, including the study of embryo development and cancer.
Tsien was born on 1 February 1952 in New York, USA. He was awarded his PhD in physiology from Cambridge University, UK, in 1977. Tsien was elected a member of the US National Academy of Sciences and the American Academy of Arts and Sciences in 1998. From 1989 he held the position of Professor and Investigator at the Howard Hughes Medical Institute, University of California, USA.