Title
Interaction of a sphingolipid with human serum albumin in the native, thermally denatured and chemically denatured states: Emission wavelength-dependent photophysical revelation
Author
Swagata Sen, Bijan K. Paul, Nikhil Guchhait
Year
2019
Journal
Journal of Molecular Liquids
Abstract
The present study exhibits a spectroscopic deciphering of the effect of a phosphosphingolipid, sphingomyelin (SM), on native as well as thermally disrupted (at ~65 °C), and urea-induced partially (in the presence of ~4.5 M urea) and completely (in the presence of ~8 M urea) chemically denatured human serum albumin (HSA). The steady-state absorption studies reveal ground-state complex formation between SM and the serum albumin. The modulations in the steady-state emission spectral profile of the Trp residue in HSA along with the time-resolved fluorescence measurements depict SM-induced modification of the micro-environment around the sole Trp residue of HSA in all the studied cases, with no significant structural modification of the protein. However, monitoring the emission wavelength-sensitive time-resolved decay behaviour of Trp, keeping the excitation wavelength constant, in the absence and presence of SM in all the cases provides an interesting result depicting a progressive increase of average fluorescence lifetime of Trp upon shifting the monitoring emission wavelength gradually to the red end of the spectrum. A significantly greater extent of increase in the average lifetime of Trp with added SM compared to that in the absence of the lipid in case of completely chemically denatured HSA than those in the other studied cases provides a probable indication that SM modifies the solvation structure of the microenvironment around Trp in presence of 8 M urea most effectively and thus leading to a significant modulation of the solvation dynamics of the flourophore in its excited-state.
Instrument
J-815, FP-8500
Keywords
Fluorescence, Protein structure, Chemical stability, Quenching, Circular dichroism, Secondary structure, Biochemistry