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Article Tianeptine Esters Derivatives: A Study of Protein-Drug Inter...

Dear Andrii Lesiuk ,

The quenching of the two Trp AA by ceriumoxide are well-described, see for example:

https://www.researchgate.net/publication/324863473_Spectroscopic_Studies_of_Interaction_of_Protein_with_Cerium_Oxide_Nanoparticles

The first thing what comes into my mind is the effect that temperate has on the conformation of BSA. Temperature-induced denaturation of BSA protein is often described in the literature, see for example:

https://pubs.acs.org/doi/10.1021/acsami.8b13749

and

https://pubmed.ncbi.nlm.nih.gov/2610859/

in other words the temperature influences the Trp-fluorescence (because one or two Trp AA are more exposed or less exposed to water etc.) and consequently also the degree of quenching by ceriumoxide.

Best regards.

This suggests a dynamic quenching, which causes an apparent increase of Ka because of more frequent collisions of BSA with nanoparticles at higher temperatures - thus, quenching may be not because of the specific interaction (e.g. with specific residues of the protein) but just random nonspecific collisions/penetration.

Thanks a lot Rob Keller for constructive and well informed answer. It really helps because I'm not a professional in the issue. In addition, Tomasz Fraczyk it turned out that the Stern-Volmer constant decreases with temperature and its value exceeds the typical for dynamic mechanism. Thus, we consider the static mechanism only.

Also, the spectra shows a red shift of the maxima with respect to the case of pure BSA solution. Maybe it also can tell sth about the process.

P.S. I would like to clarify one moment. When calculating the quenching constants I must take the intensities at the same wavelength, mustn't I?