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Title: High-Resolution Spectroscopy and Selective Photoresponse of Cryogenically Cooled Green Fluorescent Protein Chromophore Anions. Author: Andersen LH, Rasmussen AP, Pedersen HB, Beletsan OB, Bochenkova AV. Journal: J Phys Chem Lett; 2023 Jul 20; 14(28):6395-6401. PubMed ID: 37428615. Abstract: By time-resolved action spectroscopy of cryogenically cooled molecular ions, we have achieved a remarkable vibrational resolution in the photoresponse of the deprotonated green fluorescent protein (GFP) chromophore, a key molecular unit in the bioimaging of living cells. We define four characteristic spectral regions of the S0-S1 band with competing electronic and nuclear decay channels. We determine the energy barrier toward internal conversion to be ∼250 cm-1. This inhibits internal conversion and hence statistical fragmentation near the S0-S1 band origin, which is identified at 481.51 ± 0.15 nm (20768 ± 6 cm-1). The origin is red-shifted by only 221 cm-1 compared to that of wild-type GFP at 77 K. This, together with a striking agreement between the vibronic profiles of the protein and its chromophore, suggests their similar photophysics. In combination with theory, the data reveal the coexistence of mutually energy-borrowing mechanisms between nuclei and electrons mediated by specific vibrational modes.[Abstract] [Full Text] [Related] [New Search]