Unique Fluorescence Property of Human gamma-Crystallins

Jiejin Chen, Ph.D.
Senior Scientist
Takeda Pharmaceutical
Cambridge, MA 02139

Will Never Forget . . . .

Jon took me to his lab as a graduate student and guided me through the qualification exams. Jon cares about his lab members as we are part of his family. Jon is a strong advocate for science, community, and outreach program. I have been very fortunate to have Jon as my PhD thesis advisor, and mentor.

The King lab use Tryptophan fluorescence as the read-out signal to monitor the Crystallin protein unfolding and refolding process. It was observed that the tryptophan fluorescence is quenched in its native state for crystallin proteins compared to its denatured state. I utilized the site-directed mutagenesis to study the induvial and combinational fluorescence properties of the four Tryptophan inside Crystallin protein.

To investigate the quenching mechanisms, Jon set up the collaborations with Professor Patrick Callis at Montana University for computational studies. Prof. Callis provided computational supports and insights on the neighboring residues’ impact on the electron transfer rates and I did experiments to test these theoretical calculations.

The extreme quenching makes Crystallin a good model protein to be studies by the time-resolved fluorescence technique. Jon arranged my visit to Prof. Ludwig Brand’s lab at John Hopkins University to get the real experimental data on the ultra-short lifetime of the highly quenched Tryptophans by the world class lasers in Prof. Brand’s lab.

These productive collaborations led to the deep understanding of the biophysical property of crystallin for its folding and evolutions. Jon is highly respected in the Protein folding and Protein Science field. His generous manner is one of the key factors to build up good collaborations with experts in other biophysical disciplines.

Jon’s generosity, sympathy, and high standard on science, have made me a better scientist and a better person.

As a long-term Cambridge resident, I still run into Jon from time to time in the neighborhood. A few times, Jon was heading to the city hearing for community related matters. During the pandemic, Joh hosted the virtual lab reunion to discuss what we can do to contribute to the cure of Covid-19.

It has been a real honor to be part of the King Lab alumni.

Even though I don’t often discuss my time at King Lab, it has become part of me, and will never be forgotten.


  1. Chen J, Flaugh SL, Callis PR, King J. Mechanism of the highly efficient quenching of tryptophan fluorescence in human gammaD-crystallin. Biochemistry. 2006 Sep 26;45(38):11552-63.
  1. Xu J, Chen J, Toptygin D, Tcherkasskaya O, Callis P, King J, Brand L, Knutson JR. Femtosecond fluorescence spectra of tryptophan in human gamma-crystallin mutants: site-dependent ultrafast quenching. J Am Chem Soc. 2009 Nov 25;131(46):16751-7.
  1. Chen J, Toptygin D, Brand L, King J. Mechanism of the efficient tryptophan fluorescence quenching in human gammaD-crystallin studied by time-resolved fluorescence. Biochemistry. 2008 Oct 7;47(40):10705-21.
  1. Chen J, Callis PR, King J. Mechanism of the very efficient quenching of tryptophan fluorescence in human gamma D- and gamma S-crystallins: the gamma-crystallin fold may have evolved to protect tryptophan residues from ultraviolet photodamage. Biochemistry. 2009 May 5;48(17):3708-16.