Roger Yonchien Tsien (Chinese: 錢永健; pronounced /tʃɛn/, "CHEN"; February 1, 1952 – August 24, 2016) was an American biochemist.

He was a professor of chemistry and biochemistry at the University of California, San Diego,[7] and was awarded the Nobel Prize in Chemistry in 2008 for his discovery and development of the green fluorescent protein, in collaboration with organic chemist Osamu Shimomura and neurobiologist Martin Chalfie.

When he was 16, he won first prize in the nationwide Westinghouse Talent Search with a project investigating how metals bind to thiocyanate.

[12] Tsien attended Harvard College on a National Merit Scholarship, where he was elected to Phi Beta Kappa as a junior.

In 2004, Tsien was awarded the Wolf Prize in Medicine "for his seminal contribution to the design and biological application of novel fluorescent and photolabile molecules to analyze and perturb cell signal transduction.

"[21] In 2008, Tsien shared the Nobel Prize in Chemistry with Osamu Shimomura and Martin Chalfie for "the green fluorescent protein: discovery, expression and development.

"[8][22] The multicolored fluorescent proteins developed in Tsien's lab are used by scientists to track where and when certain genes are expressed in cells or in whole organisms.

[23] The first significant leap forward was a single point mutation (S65T) reported by Tsien in 1995 in Nature.

[27] Jellyfish- and coral-derived fluorescent proteins require oxygen and produce a stoichiometric amount of hydrogen peroxide upon chromophore formation.

smURFP has a large extinction coefficient (180,000 M−1 cm−1) and has a modest quantum yield (0.20), which makes it comparable biophysical brightness to eGFP and ~2-fold brighter than most red or far-red fluorescent proteins derived from coral.

On 26 October 1990, Roger Tsien et al. filed a patent of stepwise ("base-by-base") sequencing with removable 3' blockers on DNA arrays.

He has also developed fluorescent indicators for other ions such as magnesium, zinc, copper, iron, lead, cadmium, aluminum, nickel, cobalt, and mercury.

To overcome such issues, Tsien's group also developed the calmodulin-based sensor, named Cameleon.

[31] FlAsH-EDT2 is a biochemical method for specific covalent labeling of proteins harboring a tetracysteine motif (CCXXCC).

[32] Mouse experiments by Tsien's group suggest that cancer surgery can be guided and assisted by fluorescent peptides.

"[15] Roger Y. Tsien has received numerous honors and awards in his life, including: All text published under the heading 'Biography' on Fellow profile pages is available under Creative Commons Attribution 4.0 International License."