Unique, pH-dependent biphasic band shape of the visible circular dichroism of curcumin-serum albumin complex

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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 Δε496.6nm+40M-1cm-1 and Δε426.8nm-40M-1cm-1, respectively (pH 9.0, t=37°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.

Original languageEnglish
Pages (from-to)776-782
Number of pages7
JournalBiochemical and biophysical research communications
Volume301
Issue number3
DOIs
Publication statusPublished - Feb 14 2003

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Keywords

  • Circular dichroism spectroscopy
  • Curcumin
  • Exciton coupling
  • Human serum albumin
  • Induced chirality

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology

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