Site-selective binding of human serum albumin by palmatine: spectroscopic approach.
In this study, fluorescence spectroscopy in combination with UV-vis absorption spectroscopy and circular dichroism (CD) spectroscopy was employed to investigate the high affinity binding of palmatine to human serum albumin (HSA) under the physiological conditions. In the mechanism discussion it was proved that the fluorescence quenching of HSA by palmatine is a result of the formation of palmatine/HSA complex. Binding parameters calculating from Stern-Volmer method and Scatchard method showed that palmatine bind to HSA with the binding affinities of the order 10(4) L.mol(-1). The thermodynamic parameters studies revealed that the binding was characterized by negative enthalpy and positive entropy changes and the electrostatic interactions play a major role for palmatine-HSA association. Site marker competitive displacement experiments demonstrating that palmatine bind with high affinity to site I (subdomain IIA) of HSA. The specific binding distance r (2.91 nm) between donor (Trp-214) and acceptor (palmatine) was obtained according to fluorescence resonance energy transfer (FRET). Furthermore, the CD spectral result indicates that the secondary structure of HSA was changed in the presence of palmatine.
Hu
Yan-Jun
YJ
State Key Laboratory of Virology and Department of Chemistry, Wuhan University, Wuhan 430072, People's Republic of China.
Ou-Yang
Yu
Y
Dai
Chun-Mei
CM
Liu
Yi
Y
Xiao
Xiao-He
XH
D001600:Berberine Alkaloids / Q000737:chemistry* / Q000378:metabolism*; D001665:Binding Sites; D002942:Circular Dichroism; D031541:Fluorescence Resonance Energy Transfer; D006801:Humans; D011485:Protein Binding; D011487:Protein Conformation; D012709:Serum Albumin / Q000737:chemistry* / Q000378:metabolism*; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics
D001600:Berberine Alkaloids; D012709:Serum Albumin; C005413:palmatine