Microsolvation effects on the excited-state dynamics of protonated tryptophan.
To better understand the complex photophysics of the amino acid tryptophan, which is widely used as a probe of protein structure and dynamics, we have measured electronic spectra of protonated, gas-phase tryptophan solvated with a controlled number of water molecules and cooled to approximately 10 K. We observe that, even at this temperature, the bare molecule exhibits a broad electronic spectrum, implying ultrafast, nonradiative decay of the excited state. Surprisingly, the addition of two water molecules sufficiently lengthens the excited-state lifetime that we obtain a fully vibrationally resolved electronic spectrum. Quantum chemical calculations at the RI-CC2/aug-cc-pVDZ level, together with TDDFT/pw based first-principles MD simulations of the excited-state dynamics, clearly demonstrate how interactions with water destabilize the photodissociative states and increase the excited-state lifetime.
Mercier
Sébastien R
SR
Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
Boyarkin
Oleg V
OV
Kamariotis
Anthi
A
Guglielmi
Matteo
M
Tavernelli
Ivano
I
Cascella
Michele
M
Rothlisberger
Ursula
U
Rizzo
Thomas R
TR
D008958:Models, Molecular; D011522:Protons; D013816:Thermodynamics; D014364:Tryptophan / Q000737:chemistry*
D011522:Protons; D014364:Tryptophan