A mechanistic insight into the structure, conformational dynamics, affinity profile and energetics of Metanil yellow- serum protein complex

Abstract

Metanil yellow (MYL) is a toxic azo dye extensively used in food preparations and in textile industry as major colorant. It affects important biological processes leading to development of toxicity in different organ systems. Toxicological profile assessment has also revealed its potential for multi-organ toxicity. This work investigates the affinity, energetics, and structural dynamics of MYL binding with Human serum albumin (HSA) in Thyroxine binding site using multi-spectroscopic techniques and molecular simulations. Fluorescence spectroscopic studies of MYL-HSA complex at different temperatures revealed that MYL binds with HSA with stronger affinity (∼27 kJ/mole). The overall binding showed significant static quenching and was entropy driven. Circular dichroism studies showed that the secondary structure of HSA remained predominantly alpha helix. To accommodate within the Tr5 region of HSA, MYL underwent minor alterations in its conformation and position facilitated by the subtle expansion of the binding site (∼2 Å). The role of water in providing stability to the complex via water bridges and hydrogen bonds has also been investigated. Quantum Mechanics studies further revealed that the minor strain observed in the pyramidalamino nitrogen assisted MYL in the complexation.