Hi, i cannot give you the perfect solution to your problem. I dont think that you can look at environment sensitivity and solvatochromism as independent properties. I would like to hear more about the experiment and your experience with rhodamine in this regard.

What i can say though, when your only problem with rhodamine is its tautomerism, then you could use sulforhodamines like Texasred or Lissamine Rhodamine B for example.

Higher stokes shifts maybe obtained with dyes based on Coumarine like Coumarine 6 or Coumarine 153 or dyes like Dansyl migth also be useful.

Usually commercial fluorophores are trimmed to have very low stokes shift because this comes with higher fluorescece yield/sensitivity. Very large stoke shift and long fluorescence halftime are used in special applications like time resolved fluorescence and there fluorophores like Europium or Terbium Ions can be used.

Maybe have a look in the catalog of vendor that is accessible to you (Themofischer scientific for example).

Just some random ideas, hope it helps somehow :)

Hi Jan Laurenz Meidner, Omg third attempt at replying thanks to Researchgate suspecting my server is malicious!

Random ideas are appreciated and perhaps my only path forward! Texas Red is a candidate I intend to research more, thank you. Lissamine Rhodamine B is new to me, and I plan to read about it as well.

I have been thinking that my requests for both minimal solvatochromism and a large Stokes shift may be impossible. Large Stokes shifts generally come from stabilizing large excited state dipoles with polar solvents, and that same scenario will lead to variable emission energy with solvent polarity.

Our assay begins by making actin filaments (F-actin). Phalloidin stabilizes the filaments by occupying sites at the junction of two actin monomers. Rhodamine is attached by a minimal covalent linker (not pictured), and is also protein-solvated (solvent-protected, high QY). We add a protein, plasma gelsolin (pGSN). One pGSN severs one filament and then permanently attaches to that new filament end and twists the filament a little. The other filament end now has a solvent-exposed rhodamine that gets quenched, and the loss of fluorescence decreases proportional to the [pGSN]. The trouble is that the proportionality is variable, and we believe not related to the pGSN behavior (many lots of pGSN perform as well as each other). Attached figure: The assay has a maximum sample (F-actin with no pGSN; all rhodamine is solvent-protected), a minimum sample (rhodamine phalloidin with no actin; all rhodamine is solvent-exposed), and a series of samples with F-actin and some concentration of pGSN. We want consistent relative fluorescence loss (purple arrow ÷ green arrow). Since a small shift in where rhodamine sits in F-actin could bring it closer to, say, a hydrophobic residue and make it go dark, I would like a new fluorophore that simplifies the photophysics by avoiding leuco states. I will still need QY contrast between solvent-protected and -exposed states, and would like to avoid substantial photobleaching if I can.