Binding of all-trans retinoic acid to human serum albumin: fluorescence, FT-IR and circular dichroism studies.
All-trans retinoic acid derived from vitamin A is an essential component for the modulation of angiogenesis, the process of blood vessel formation. We have investigated the binding of all-trans retinoic acid to the carrier protein, human serum albumin (HSA) under physiological conditions. Fluorescence quenching methods in combination with Fourier transform infrared (FT-IR) spectroscopy and circular dichroism (CD) spectroscopy were used for the biophysical studies. The binding parameters were determined by a Scatchard plot and the results found to be consistent with those obtained from a modified Stern-Volmer equation. From the thermodynamic parameters calculated according to the van't Hoff equation, the enthalpy change DeltaH(0) and entropy change DeltaS(0) are found to be 106.17 and 106.14J/molK, respectively. These values suggest that apart from hydrophobic interactions electrostatic interactions are present. Changes in the CD spectra and FT-IR spectra were observed upon ligand binding along with a significant degree of tryptophan fluorescence quenching on complex formation. Docking studies performed substantiated our experimental findings and it was observed that all-trans retinoic acid hydrogen bonded with Trp 214 and Asp 451 residues of subdomain IIA and IIIA of HSA, respectively.
Department of Chemistry, Indian Institute of Technology, Kharagpur 721302, India.
Tushar Kanti
TK
Maiti
Kalyan Sundar
KS
Ghosh
Joy
J
Debnath
Swagata
S
Dasgupta
D002942:Circular Dichroism / Q000379:methods*; D019277:Entropy; D006358:Hot Temperature; D006801:Humans; D007700:Kinetics; D008958:Models, Molecular; D012709:Serum Albumin / Q000378:metabolism*; D013050:Spectrometry, Fluorescence / Q000379:methods*; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D055672:Static Electricity; D013816:Thermodynamics; D014212:Tretinoin / Q000737:chemistry* / Q000378:metabolism; D014364:Tryptophan / Q000737:chemistry; D014801:Vitamin A / Q000378:metabolism
D012709:Serum Albumin; D014801:Vitamin A; D014212:Tretinoin; D014364:Tryptophan