Interaction of reactive Red195 with human serum albumin: Determination of the binding mechanism and binding site by spectroscopic and molecular modeling methods

Reactive Red195 (RR195) was the first synthetic color patented for textile dying in 1856. Azo dyes have arisen considerable environmental concerns in recent decades due to the large volume of water they require throughout the coloring process and the polluted of industrial sewage. Azo dye due to their chemical composition, including aromatic rings, azoic linkages, and amino groups, are not bio-degradable and exceedingly resistant in the aquatic environment, posing an acute threat to human health. In this investigation, to estimate the toxicity of the RR195 at the protein level, the influences of RR195 on human serum albumin (HSA) were described by molecular modeling, steady-state fluorescence, ultraviolet-visible spectroscopy (UV–Vis), circular dichroism spectroscopy (CD), and Thermal stability (Tm). The alteration in entropy (∆S) and enthalpy (∆H) showed that hydrophobic forces were the dominant intermolecular forces in the binding of the RR195 to HSA. The binding constant of HSA–RR195 is high, presenting that RR195, which has a high affinity to HSA. The changes of protein secondary structure in the presence of the RR195 approved by CD spectroscopy method. A small reduction in the RG value of the HSA-RR195 system demonstrated a conformational difference in the compaction of HSA.