title: Binding of the alkaloid aristololactam-β-D-glucoside and daunomycin to human hemoglobin: spectroscopy and calorimetry studies.
abstract: The interaction of the plant alkaloid aristololactam-β-D-glucoside (ADG) and the anticancer agent daunomycin (DAN) with human hemoglobin was studied by different spectroscopic and calorimetric methods. The binding affinity values of ADG and DAN, estimated from spectroscopic experiments, were 3.79 × 10(4) and 6.68 × 10(4) M(-1), respectively. From circular dichroism, 3D fluorescence, and FTIR studies it was observed that, DAN induced stronger conformational changes than ADG in the protein. From synchronous fluorescence spectroscopy results, a pronounced shift in the maximum emission wavelength of tyrosine residues was observed in both cases suggesting that the drugs changed the polarity around tyrosine residues with marginal change around the tryptophan residues. The thermodynamics of the binding interaction analyzed using microcalorimetry presented single binding events that were exothermic in nature in both cases. The binding was driven by large positive standard molar entropy changes with small favorable enthalpy contributions. Negative heat capacity changes in both cases are correlated to the involvement of significant hydrophobic forces in the complexation process. The affinity of DAN to Hb was higher than that of ADG.
authors.affiliation: a Biophysical Chemistry Laboratory, Chemistry Division , CSIR-Indian Institute of Chemical Biology , 4, Raja S.C. Mullick Road, Kolkata 700 032 , India.
authors.forename: Abhi
authors.initials: A
authors.lastname: Das
authors.affiliation: a Biophysical Chemistry Laboratory, Chemistry Division , CSIR-Indian Institute of Chemical Biology , 4, Raja S.C. Mullick Road, Kolkata 700 032 , India.
authors.forename: Gopinatha
authors.initials: G
authors.lastname: Suresh Kumar
mesh_terms: D034341:Aristolochic Acids / Q000737:chemistry* / Q000378:metabolism; D002151:Calorimetry / Q000379:methods; D003630:Daunorubicin / Q000737:chemistry* / Q000378:metabolism; D005960:Glucosides / Q000737:chemistry* / Q000378:metabolism; D006454:Hemoglobins / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D015394:Molecular Structure; D011485:Protein Binding; D013057:Spectrum Analysis / Q000379:methods; D013816:Thermodynamics
chemical_list: D034341:Aristolochic Acids; D005960:Glucosides; D006454:Hemoglobins; C062008:aristololactam-glucoside; D003630:Daunorubicin
keywords: aristololactam-β-D-glucoside; daunomycin; human hemoglobin; spectroscopy; thermodynamics