N-Acetylcysteine versus arsenic poisoning: A mechanistic study of complexation by molecular spectroscopy and density functional theory.

[Display omitted] • Role of N-acetylcysteine (NAC) as an antitoxin of arsenic poisoning. • Formation of a stable water-soluble complex between NAC and arsenic. • Raman spectral study to find the molar ratio of NAC:As for stable complexation. • Synthesis and characterization of NAC:As::3:1 complex by Raman and SERS analyses. • DFT based calculations to elucidate the structural changes during complexation. Arsenic poisoning is a critical health hazard. Here we investigate the mechanism that enables N-Acetylcysteine (NAC), an antioxidant drug, to act as an antitoxin of arsenic poisoning. Concentration dependent Raman spectral analysis determined the precise molar ratio (3:1) at which a water-soluble complex between NAC and arsenic is formed. Stability and geometry of the complex was inferred by characterizing the synthesized complex using Raman and surface enhanced Raman spectroscopic (SERS) techniques. Density functional theory (DFT) based studies were performed to understand the nature of interaction between NAC and arsenic at molecular level, as well as to elucidate the structural changes taking place during complexation. The combined experimental and theoretical study suggests that a stable complex between NAC and arsenic is formed in three steps. This study highlights the high affinity of NAC towards arsenic and may help to identify the way NAC is expected to protect biomolecules from the toxic effect of arsenic. [ABSTRACT FROM AUTHOR]