Albany 2015:Book of Abstracts

Albany 2015
Conversation 19
June 9-13 2015
©Adenine Press (2012)

Interaction of some food colorants with human hemoglobin: A biophysical study

Carmoisine, amaranth and tartrazine (Fig. 1) are toxic azo dyes which are widely used as food colorants. Interaction of these toxic food colorants with hemoglobin was studied employing a variety of biophysical tools. The binding caused hypochromic changes in the absorption spectrum of hemoglobin and led to quenching of its fluorescence spectrum. The mechanism of quenching was deduced to be static in nature from temperature dependent fluorescence data.


The equilibrium constant for the binding reaction was in the range 104-105 M-1 at 298.15 K. A 1:1 stoichiometry of complexation was established between these molecules and hemoglobin. Synchronous fluorescence studies revealed that the polarity around Trp residues of the protein was significantly increased upon complexation whereas those around Tyr residues remained virtually unchanged. The binding induced structural changes as evealed from 3D fluorescence, synchronous fluorescence, FT-IR and circular dichroism spectroscopy. Hydrophobic probe ANS displacement assay was used to ascertain the binding site of these colarants. The binding was revealed tobe favored by large positive entropy changes and small but favorable enthalpy changes. The negative standard molar heat capacity values in conjunction with the enthalpy-entropy compensation behavior suggested the involvement of dominant hydrophobic forces in the binding process. Detailed structural and energtics aspects from the biophysical perspectives shall be discussed in the light of their known toxicity.

This research has been supported by network project GenCODE (BSC0123) of Council of Scientific and Industrial Research, Govt. of India.

Anirban Basu
Gopinatha Suresh Kumar

Biophysical Chemistry Laboratory
CSIR-Indian Institute of Chemical Biology
Kolkata 700 032 India

Ph: +91 33 2499-5798
Fax: +91 33 2472 3967