AIMD maps GFP's excited-state proton shuttle
TD-DFT AIMD and wavelet spectra show GFP ESPT is concerted once low-frequency chromophore modes planarize the H-bond wire.
Source
The mechanism of a green fluorescent protein proton shuttle unveiled in the time-resolved frequency domain by excited state <i>ab initio</i> dynamics
Study at a glance
- Design
- Computational / modelling — ONIOM QM/MM AIMD of wtGFP excited-state proton transfer with wavelet spectral analysis
- N
- Five S1 trajectories; ESPT within ~1 ps in four runs — no experimental sample N
- Population
- Wild-type green fluorescent protein chromophore environment
- Outcome
- Excited-state proton-transfer timing and vibrational signatures
Structured fields used in claim comparison tables when every cited study has a complete layer.
What they did
Authors ran ONIOM QM/MM Born–Oppenheimer AIMD of wtGFP in S0 and S1 (B3LYP vs TD-CAM-B3LYP) and analysed O–H, C–O/C–N and dihedral trajectories with Morlet wavelets versus FSRS.
What they found
Four of five S1 runs transferred the proton within 1 ps (720 fs in TRJI; 350, 380, 980 fs in II–IV). O–O contacts shorten in 15–20 fs; O–H stretches redshift; C–O/C–N bands beat out of phase every ~250 fs. Twist modes drop from 146 to 101 cm–1 and His148 approaches Otyr before transfer.
The limits
What it doesn't show
Kinetics are faster than the experimental 3/10 ps phases (DFT barrier underestimation, no MM polarisation); nonadiabatic hops at longer times are omitted; only four successful S1 trajectories.
Key terms
- ESPT
- Excited-state proton transfer from the GFP chromophore along a hydrogen-bond wire.
- ONIOM QM/MM
- Layered model with TD-DFT on the chromophore pocket and AMBER on the rest of GFP.
- Wavelet transform
- Time–frequency analysis that tracks instantaneous vibrational bands along an AIMD trajectory.
- FSRS
- Femtosecond stimulated Raman spectroscopy whose C–O/C–N out-of-phase beats the AIMD reproduces.
- HBDI
- p-Hydroxybenzylideneimidazolinone, the GFP chromophore in A (neutral) and I*/B (anionic) forms.
Flashcards
Research intelligence for this paper
See its role on concept claims, tensions it is part of, placement history, and related discoveries.
Quiz yourself
GFP ESPT final acceptor is:
Common questions
Who donates and who accepts the proton?
Chromophore phenolic OH to crystallographic water to Ser205 to Glu222.
Is the shuttle stepwise?
Concerted and nearly synchronous in all reactive S1 trajectories.
What promotes ESPT?
Photoactivated low-frequency modes that planarize the oxygen wire plus His148 approach.
How is S1 modelled?
TD-CAM-B3LYP/6-31+G(d,p) high layer, AMBER low layer.
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