Devising Efficient Red‐Shifting Strategies for Bioimaging: A Generalizable Donor‐Acceptor Fluorophore Prototype

Abstract

Long emission wavelengths, high fluorescence quantum yields (FQYs), and large Stokes shifts are highly desirable features for fluorescent probes in biological imaging. However, the current development of many fluorescent probes remains largely trial-and-error and lacks efficiency. Moreover, to achieve far-red/near-infrared emission, a significant extension in the p-conjugation is usually adopted but accompanied by other drawbacks such as fluorescence loss. In this review, we discuss an effective red-shifting strategy built upon the green fluorescent protein chromophore, which enables a synergistic tuning of both the electronic ground and excited states. This approach could shorten the path toward redder emission in comparison to the conventional intramolecular charge transfer (ICT) strategy. We envision that this spectroscopy and computation-aided strategy may advance the noncanonical fluorescent protein design and be generalized to various fluorophore scaffolds for redder emission while preserving other superior properties such as high FQYs.[a] C.

Ultrafast Dynamics and Photoresponse of a Fungi‐Derived Pigment Xylindein from Solution to Thin Films

“…From the calculated absorption spectra (Figure S3) of the protonated, deprotonated, and ESIPT product, the latter two species display a similar redshift from the protonated form. Moreover, both the deprotonated and I forms acquire significant charge on the central oxygen atoms (O2 and O5 in Table S1), so the electron donating capability of these oxygens may play a pivotal role that induces the redshift [8] . These results support our calculation approach (Supporting Information).…”

“…Moreover,b oth the deprotonated and If orms acquire significant charge on the central oxygen atoms (O2 andO 5i nT able S1), so the electron donating capability of these oxygens may play ap ivotal role that induces the redshift. [8] These resultss upport our calculation approach (Supporting Information). In contrast, the xylindein thin films display one dominant emission peak at ar edder wavelength (909 nm) that originates from an excimer state.…”

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

“…Increasing the electron density around or at the phenolate ring such as incorporating π-π stacking (e.g., an adjacent Y203 here) or electron-donating groups would redshift the anionic chromophore emission. 44,65 On the ion-sensing front, the low binding affinity (Kd~300-400 mM at pH=5-6) makes the current phiYFP unsuitable for intracellular detection of Cl − concentrations without further engineering. In order to improve the binding affinity, one direct approach is to strengthen the electrostatic interaction between the anion and protein residues that constitute the binding pocket.…”

Developing Bright Green Fluorescent Protein (GFP)‐like Fluorogens for Live‐Cell Imaging with Nonpolar Protein−Chromophore Interactions

“…[8][9][10] It was directly engineered from the GFP chromophore (p-HBI) [11] using our double-donor-oneacceptor (DDA) strategy that can effectively red-shift emission wavelengths. [12] Interestingly, the electron-donating group (EDG) À OMe (ortho to the hydroxyl, "DD") and an electronwithdrawing group (EWG) À CF 3 ("A") as well as another À OMe (meta to hydroxyl, ortho to the methine bridge) cause remarkable FE of the anionic chromophore from solution to the protein environment of FAST besides a redshift in wavelength (Figure S1). The analogues without the extra donor (2OM-HBI-2T) or acceptor (25DOM-HBI, Figure 1B) exhibit notably smaller FE, suggesting that our DDA strategy is effective in promoting a large FE.…”