title: Berberine, a strong polyriboadenylic acid binding plant alkaloid: spectroscopic, viscometric, and thermodynamic study.
abstract: The interaction of berberine with single stranded poly(rA) structure was investigated using a combination of spectrophotometric, spectrofluorimetric, circular dichroic, viscometric, and thermodynamic studies. The interaction process was characterized by typical hypochromic and bathochromic effects in the absorption spectrum of berberine, enhancement of fluorescence intensity of berberine, increase of viscosity, and perturbation of circular dichroic spectrum of single stranded poly(rA). Scatchard plot obtained from spectrophotometric analysis showed that berberine bound strongly to single stranded poly(rA) in a non-cooperative manner. In contrast, berberine does not show any significant effect (i) in its absorbance and fluorescence spectra on binding to double stranded poly(rA), (ii) alter the circular dichroic spectrum of double stranded poly(rA), or (iii) increase of viscosity of double stranded poly(rA) indicating that it does not bind at all to double stranded poly(rA) structure. Thermodynamic parameters indicated that the binding of the alkaloid to single stranded poly(rA) is an endothermic process and entropy driven. All these findings, taken together clearly support that berberine binds strongly to single stranded poly(rA) structure by a mechanism of partial intercalation leading to its use in gene regulation in eukaryotic cells.
authors.affiliation: Biophysical Chemistry Laboratory, Indian Institute of Chemical Biology, 4 Raja S.C. Mullick Road, Kolkata 700 032, India.
authors.forename: Ram Chandra
authors.initials: RC
authors.lastname: Yadav
authors.forename: Gopinatha Suresh
authors.initials: GS
authors.lastname: Kumar
authors.forename: Kakali
authors.initials: K
authors.lastname: Bhadra
authors.forename: Prabal
authors.initials: P
authors.lastname: Giri
authors.forename: Rangana
authors.initials: R
authors.lastname: Sinha
authors.forename: Sumana
authors.initials: S
authors.lastname: Pal
authors.forename: Motilal
authors.initials: M
authors.lastname: Maiti
mesh_terms: D001599:Berberine / Q000138:chemical synthesis* / Q000378:metabolism; D002942:Circular Dichroism; D009691:Nucleic Acid Denaturation; D009994:Osmolar Concentration; D011061:Poly A / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics; D014783:Viscosity
chemical_list: D001599:Berberine; D011061:Poly A