We have designed a calcium sensor CatchER (a GFP-based calcium indicator to monitor calcium dynamics in high calcium concentration environment) with a capability for monitoring calcium ion responses in various types of cells. The intrinsic optical properties of CatchER are based on the acid-base equilibria of its chromophore in the ground and the excited states.  The Ca-sensing action of CatchER involves the calcium-induced changes of its prototropic properties detected by the absorption and the emission spectroscopies.  Addition of calcium inhibited the proton transfer both in ground and in the excited-state (ESPT). Interestingly, a strong inhibition on the ESPT non-adiabatic geminate recombination by calcium and in protic (vs deuteric) medium was detected.  Molecular mechanisms of these phenomena will be discussed.  Kaede-like fluorescent proteins possess a complex photochemical and photophysical behavior, which requires further investigations. In particular, little has been done in the field of ultrafast time-resolved studies on this protein class.  In this work, we studied the ultrafast photoinduced kinetics of Dendra2 using femtosecond transient absorbance spectroscopy. As a part of this study, an optical setup that allows illumination of a sample using two consecutive ultrafast photoconverting pulses with a variable delay was utilized. This made possible to study the potential evolution paths of the system during Dendra2 photoconversion (PC), via absorption of one and two photons. A comparative PC study via pulsed or continuous-wave excitation at various wavelengths will be reported.

Ultrafast photoinduced processes in fluorescent proteins: Proton geminate recombination and two-photon photoconversion

247th National Meeting (2014)

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