|Title||Unraveling ultrafast photoinduced proton transfer dynamics in a fluorescent protein biosensor for Ca(2+) imaging.|
|Publication Type||Journal Article|
|Year of Publication||2015|
|Authors||Tang, Longteng, Weimin Liu, Yanli Wang, Yongxin Zhao, Breland G. Oscar, Robert E. Campbell, and Chong Fang|
|Date Published||2015 Apr 20|
Imaging Ca(2+) dynamics in living systems holds great potential to advance neuroscience and cellular biology. G-GECO1.1 is an intensiometric fluorescent protein Ca(2+) biosensor with a Thr-Tyr-Gly chromophore. The protonated chromophore emits green upon photoexcitation via excited-state proton transfer (ESPT). Upon Ca(2+) binding, a significant population of the chromophores becomes deprotonated. It remains elusive how the chromophore structurally evolves prior to and during ESPT, and how it is affected by Ca(2+) . We use femtosecond stimulated Raman spectroscopy to dissect ESPT in both the Ca(2+) -free and bound states. The protein chromophores exhibit a sub-200 fs vibrational frequency shift due to coherent small-scale proton motions. After wavepackets move out of the Franck-Condon region, ESPT gets faster in the Ca(2+) -bound protein, indicative of the formation of a more hydrophilic environment. These results reveal the governing structure-function relationship of Ca(2+) -sensing protein biosensors.
|Grant List||/ / Canadian Institutes of Health Research / Canada|