title: Unique, pH-dependent biphasic band shape of the visible circular dichroism of curcumin-serum albumin complex.
abstract: Interaction between the plant derived polyphenolic type curcumin molecule having anticarcinogenic, antiinflammatory, and antioxidant activities, and human serum albumin was studied at different pH values by circular dichroism (CD) and electronic absorption spectroscopy. The weak, induced CD spectrum of curcumin-HSA complex measured at pH 7.4 in the visible spectral region shows striking changes upon alkalization; CD spectra collected between pH 7.7 and 9.3 exhibit characteristic, oppositely signed CD band pair according to the visible absorption band of HSA-bound curcumin. At 0.3 curcumin/HSA molar ratio, typical molar CD values are Delta epsilon (496.6nm)+40M(-1)cm(-1) and Delta epsilon (426.8nm)-40M(-1)cm(-1), respectively (pH 9.0, t=37 degrees C). The induced optical activity is attributed to a bent, right-handed chiral conformation of the HSA-bound curcumin molecule within which intramolecular exciton coupling occurs between the electric dipole transition moments of the dissymmetrically juxtaposed feruloyl chromophores. Deprotonation of phenolic OH group(s) of curcumin seems to be the reason leading to the conformational alteration of HSA-bound curcumin.
authors.affiliation: Department of Molecular Pharmacology, Institute of Chemistry, Chemical Research Center, Budapest, Hungary. zsferi@chemres.hu
authors.forename: Ferenc
authors.initials: F
authors.lastname: Zsila
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Bikádi
authors.forename: Miklós
authors.initials: M
authors.lastname: Simonyi
mesh_terms: D002942:Circular Dichroism; D003474:Curcumin / Q000737:chemistry* / Q000378:metabolism; D000431:Ethanol / Q000737:chemistry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007536:Isomerism; D046911:Macromolecular Substances; D011487:Protein Conformation; D012709:Serum Albumin / Q000737:chemistry* / Q000378:metabolism; D012997:Solvents / Q000737:chemistry; D013053:Spectrophotometry; D013056:Spectrophotometry, Ultraviolet
chemical_list: D046911:Macromolecular Substances; D012709:Serum Albumin; D012997:Solvents; D000431:Ethanol; D003474:Curcumin