Title
Calorimetric and Spectroscopic Detection of Interaction Between a Diazo Dye and Human Serum Albumin
Author
Bhargav Patel, Kagan Kerman
Year
2018
Journal
Analyst
Abstract
Dye effluents are one of main sources of concern causing water pollution. Azo dyes, most widely applied colorants, are particularly difficult to degrade. Exposure of such dyes in aquatic environment is hazardous to human health and biota due to their intrinsic harmful mutagenic and carcinogenic properties. Congo Red (CR) is an anionic and synthetic diazo dye, which is recalcitrant to biodegradative process and metabolizes to produce a potential carcinogen. Research on the interaction of this toxic dye with serum albumin, as transport protein, is of paramount significance because the physiological and toxicological behaviour of the dye in vivo are associated with its interactive characteristics with the proteins. In this regard, a detailed binding profile of CR with human serum albumin (HSA) was studied using isothermal titration calorimetry (ITC) along with various spectroscopic and microscopic methods. Thermodynamic results from ITC indicated that the CR-HSA non-covalent interaction occured primarily due to favorable entropy and unfavorable enthalpy with Ka of 106 M-1 at lower concentrations and 105 M-1 at higher concentrations. Steady-state fluorescence data revealed that the intrinsic fluorescence of HSA was quenched in the presence of CR via static quenching mechanism. Using Förster’s non-radioactive energy transfer theory (FRET) the specific binding distance r (2.73 nm) between donor (Trp-214 from HSA) and acceptor (CR) was calculated. Our preliminary results indicated that CR had high affinity to HSA, which can have significant implications on the distribution and elimination of this toxic dye upon exposure.
Instrument
J-815
Keywords
Circular dichroism, Secondary structure, Ligand binding, Protein folding, Biochemistry