The quenching of the fluorescence signal is dependent on energy transfer, complex-formation, excited state reactions and collisional quenching ( collisional frequency) exciting electron to higher energy states. it is also related to energy transfer of excited TRP residue to nearby residues.

For example, we mutated phenylalanine residue that locates close to TRP to alanine. The energy transfer process is more efficient in TRP --> PHE than TRP -->ALA in that system.

References 

Lakowicz JR (2006) Principles of Fluorescence Spectroscopy: Principles of Fluorescence Spectroscopy, by J.R.∼Lakowicz.∼ISBN 0–387–31278–1.∼ Berlin: Springer, 2006. 

Vivian JT, Callis PR (2001) Mechanisms of tryptophan fluorescence shifts in proteins. Biophys J 80: 2093–2109.

https://www.dropbox.com/s/fzkeu46bf3xi0s8/10.1007%400-306-47058-62.pdf?dl=0

https://www.dropbox.com/s/x0pneo2kc48fvsz/10.1007%252F978-0-387-46312-4_16.pdf?dl=0

I hope it helps to understand your system better!

Thank you so much

Follow some of my publications in pubmed. We regularly use it.

Hi Aishwarya,

To check Trp quenching for protein-ligand interaction, you can use a constant conc of the protein and do continuous quenching by increasing the conc of the respective ligand. Depending on the position of the Trp residues in your protein of interest you will get increased or decreased Trp fluorescence intensity which later can be put in a Stern-Volmer equation and you can determine the affinity of protein-ligand interaction. Please check these articles for details:

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