Excitation ratiometric chloride sensing in a standalone yellow fluorescent protein is powered by the interplay between proton transfer and conformational reorganization

Abstract

Natural and laboratory-guided evolution has created a rich diversity of fluorescent protein (FP)-based sensors for chloride (Cl−). To date, such sensors have been limited to the Aequorea victoria green fluorescent...

A Novel Dialkylamino GFP Chromophore as an Environment-Polarity Sensor Reveals the Role of Twisted Intramolecular Charge Transfer

“…It is likely because of the same polarization instead of polarizations at the magic angle (54.7 • ) for pump and probe pulses during the measurement. However, our main focus was to collect fs-TA spectra with high signal-to-noise and perform a quantitative analysis using the retrieved fluorescence time constant (the longest time constant on the ns timescale, colored in green in Figure 3a and Figure S7 for compound 1) and the aforementioned FQY (see more details below), while this dimethylamino group twisting motion differed from the two-ring twisting motions of the chromophore backbone that lead to a more red-shifted stimulated emission band with much shorter lifetimes in solution [39,57,58]. The last green EADS was associated with the decay of FS with an apparent lifetime of 0.78 ns.…”

[LiCl2]− Superhalide: A New Charge Carrier for Graphite Cathode of Dual‐Ion Batteries

“…The structures were first optimized with 3–21G then 6–31G basis sets. [ 46 ] The 6–31G(d,p) basis sets were used for [Li(H 2 O) 4 ] + and [Li(H 2 O) 3 Cl] due to their positive and neutral charge, while the diffuse function was added for heavy atoms on [Li(H 2 O) 2 Cl 2 ] − , [Li(H 2 O)Cl 3 ] 2− , and [LiCl 4 ] 3− because of the negative charge. No imaginary frequency was observed for the optimized structures (see Figure 1c–f in main text).…”

“…The structures were first optimized with 3-21G then 6-31G basis sets. [46] ICP-MS Measurements: Graphite electrode samples were weighed out and leached in 6 mL of 8 M ("charged") or 13 M ("discharged") ultrapure nitric acid (Aristar Ultra grade, BDH Chemical). After a period of ≥4 days, the leaches were diluted for analysis.…”

Fluorescence Modulation by Ultrafast Chromophore Twisting Events: Developing a Powerful Toolset for Fluorescent-Protein-Based Imaging

“…These transient electronic bands can thus be readily obtained in fs-TA data. Meanwhile, FSRS provides simultaneously high spectral (typically <20 cm –1 ) and temporal (<30 fs) resolutions, along with the broad wavelength tunability enabling targeted ,, and dynamic ,, resonance Raman enhancement (conveniently guided by fs-TA results), which has been used to study many biological systems including ultrafast twisting events in rhodopsin, phytochrome, and FP systems. ,,, The synergy between fs-TA and FSRS also allows deeper insights into the FSRS band intensity dynamics with a clearer distinction , between population change (e.g., deprotonation, chemical speciation) and resonance effect (e.g., shift of TA band, change of electronic structure), as we previously demonstrated for a photoacid (pyranine) in various solvents with comparative dynamics plots of the TA and FSRS bands. , In essence, the Raman approach is advantageous over time-resolved IR (TRIR) techniques mainly due to the unique resonance Raman enhancement effect, allowing a “laser-sharp” focus on steady-state and time-resolved chromophore motions at the chemical-bond level, whereas multiple overlapped IR bands from surrounding amino acids observed in TRIR besides the chromophore modes could complicate spectral analysis. Detailed information and expanded discussions about FSRS methodology with diverse applications can be found in several recent reviews. ,,,, …”

“…However, most of these studies were focused on anionic p -HBDI and/or its derivatives in vacuo or in solution, and debates remain regarding the exact light-induced pathways, such as sequential or parallel roles played by P-ring and imidazolinone ring (I-ring) twisting motions (see Figure , left panel), and whether or not these processes are barrierless on ultrafast time scales . In contrast, our recent works have targeted and directly observed the onset, progression, and outcome of the chromophore twisting events inside the protein matrix in a series of FP derivatives and FP-based biosensors, ,− as well as photoconvertible and photoswitchable proteins …”