Interaction of toxic azo dyes with heme protein: biophysical insights into the binding aspect of the food additive amaranth with human hemoglobin.
A biophysical study on the interaction of the food colorant amaranth with hemoglobin was undertaken. Spectrophotometric and spectrofluorimetric studies proposed for an intimate binding interaction between the dye and the protein. The dye quenched the fluorescence of the protein remarkably and the mechanism of quenching was found to be static in nature. Synchronous fluorescence studies suggested that the polarity around the tryptophan residues was altered in the presence of amaranth whereas the polarity around tyrosine residues remained largely unaltered. 3D fluorescence, FTIR and circular dichroism results suggested that the binding reaction caused conformational changes in hemoglobin. The negative far-UV CD bands exhibited a significantly large decrease in magnitude in the presence of amaranth. From calorimetry studies it was established that the binding was driven by a large positive entropic contribution and a small but favorable enthalpy change.
Biophysical Chemistry Laboratory, CSIR-Indian Institute of Chemical Biology, Kolkata 700 032, India.
Anirban
A
Basu
Biophysical Chemistry Laboratory, CSIR-Indian Institute of Chemical Biology, Kolkata 700 032, India. Electronic address: gskumar@iicb.res.in.
Gopinatha Suresh
GS
Kumar
D000548:Amaranth Dye / Q000737:chemistry*; D001391:Azo Compounds / Q000737:chemistry*; D001703:Biophysics; D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D005505:Food Coloring Agents / Q000737:chemistry*; D006420:Hemeproteins / Q000737:chemistry*; D006454:Hemoglobins / Q000737:chemistry*; D006801:Humans; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared
D001391:Azo Compounds; D005505:Food Coloring Agents; D006420:Hemeproteins; D006454:Hemoglobins; D000548:Amaranth Dye
Amaranth; Binding; Hemoglobin; Spectroscopy; Thermodynamics