First Step toward a Universal Fluorescent Probe: Unravelling the Photodynamics of an Amino–Maleimide Fluorophore

Abstract

Continuous advancements in biophysics and medicine at the molecular level make the requirements to image structure-function processes in living cells ever more acute. While fluorophores such as the green fluorescent protein have proven instrumental toward such efforts, the advent of nondiffraction limited microscopy limits the utility of such fluorescent tags. Monoaminomaleimides are small, single molecule fluorophores that have been shown to possess stark variations in their emission spectra in different solvent environments, making them a potentially powerful tool for a myriad of applications. The ability to "autotune" fluorescence according to different media allows for a probe capable of working in all regions of a cell, or accurately characterizing the purity of an environment. In this work, we present ultrafast pump-probe studies of a model monoaminomaleimide, 1-methyl-3-(methylamino)-1H-pyrrole-2,5-dione, and demonstrate how fluorescence quenching in polar protic solvents is caused by electron driven proton transfer from the solvent to the fluorophore. Armed with this knowledge, the present study acts as a first step for the rational design of future maleimides, potentially moving toward creating a universal fluorophore with tunable efficiency, dependent on environment.

Enhancing the Anti‐Solvatochromic Two‐Photon Fluorescence for Cirrhosis Imaging by Forming a Hydrogen‐Bond Network

“…In accord with the “energy gap law” energy is released through electron transition from excited states to the empty orbitals . Excited‐state proton transfer mostly occurs in protic polar solvents, where protons migrate from solvents to the fluorophores and quench the excited electrons (Figure A) . On the other hand, D–A type fluorophores rely on intramolecular charge transfer (ICT) for bright emission .…”

“…[10] Excited-state proton transfer mostly occurs in protic polar solvents,where protons migrate from solvents to the fluorophores and quench the excited electrons ( Figure 1A). [11] On the other hand, D-A type fluorophores rely on intramolecular charge transfer (ICT) for bright emission. [12] Thef luorescence properties might be jeopardized if the D-A group were overly truncated.…”

Rational design of substituted maleimide dyes with tunable fluorescence and solvafluorochromism

“…This is consistent with previous work which shows that the hydrogen bonding between protic solvents and the C O group in maleimides causes quenching effects through electron driven proton transfer from the solvent to the fluorophore. 38 In non-polar solvents such as cyclohexane, bright emission with the highest Φ f was observed, likely as a consequence of the suppression of twisted intramolecular changer transfer (TICT) in the maleimide rings. 9 …”

Enhancing the Anti‐Solvatochromic Two‐Photon Fluorescence for Cirrhosis Imaging by Forming a Hydrogen‐Bond Network

“…[9] In accord with the "energy gap law" energy is released through electron transition from excited states to the empty orbitals. [11] On the other hand, D-A type fluorophores rely on intramolecular charge transfer (ICT) for bright emission. [11] On the other hand, D-A type fluorophores rely on intramolecular charge transfer (ICT) for bright emission.…”

“…[15] It is noteworthy that most fluorophores are quenched by hydrogen bonds,with the GFP chromophore being an exception only in the protein pocket. [11] Our design aims at incorporating all the three features of GFP chromophore with an emphasis on forming hydrogen bonds in the open solvent environment.…”