Abstract:
While excited-state proton transfer (ESPT) underlies the bright fluorescence from wild-type green fluorescent protein (wt-GFP), the large Stokes shifts in certain red fluorescent proteins (LSS-RFP) imply a more intricate excited-state photophysical behavior. Our earlier work showed that mKeima exhibits dual emission only at 77 K; a similar trend was also observed in LSSmKates. In contrast, mBeRFP displays dual emission at room temperature and triple emission at 77 K, the first reported example of triple emission in a fluorescent protein. To gain insight into the ultrafast relaxation of different conformers in the excited state, we performed femtosecond transient absorption spectroscopy (fs-TAS) in both normal and deuterated buffers. This work demonstrates the key role of ESPT in LSSmKate1 and LSSmKate2, which differ by a point mutation, and reports temperature-sensitive local and distant emissions, including dual and triple fluorescence in mBeRFP. Combining the results, we conclude that the branching of the excited-state population through multiple conical intersections leads to LSS in LSS-RFP. The results are further supported by electronic structure calculations. If time permits, I will discuss speculations on assigning the picosecond fluorescence kinetics observed in wt-GFP to proton transfer, and why we need to think outside the box to pinpoint the mechanistic details.
Biography:
Dr. Arijit K. De completed his BSc (2003) from the University of Calcutta, and both MSc (2005) and PhD from IIT Kanpur. He was a postdoctoral fellow at the University of California Berkeley. In 2014, he joined IISER Mohali, where he is now an Associate Professor in the Department of Chemical Sciences. The central theme of research in the "Condensed Phase Dynamics" group at IISER Mohali, led by Dr. Arijit K. De, is to explore, through a combination of experiments and theories, a multitude of multidisciplinary problems spanning chemistry, biophysics, and condensed matter physics. His group developed a couple of cutting-edge spectroscopic techniques beyond widely used, commercially available femtosecond pump-probe (or transient absorption) spectroscopy, namely 'two-dimensional electronic spectroscopy' and '(time-resolved) impulsive Raman spectroscopy'. The group also pioneered the study of the role of optical and thermal nonlinearities in laser trapping under femtosecond-pulsed excitation. Quite recently, they developed a 'laser beam-shaping (with computer-generated holograms)' apparatus.
Seminar Series by the NYU-ECNU Center for Computational Chemistry at NYU Shanghai
This event is open to the NYU Shanghai, NYU, ECNU community and the computational chemistry community.