Revealing Organophosphorus and Carbamate Interactions with Albumin Using ¹H NOE Pumping NMR Technique

In this work, the capability of the ¹H nuclear Overhauser effect (NOE) pumping NMR technique was applied to elucidate the atomic-level binding interaction between the bovine serum albumin (BSA) and four toxic compounds: amiton, dimethoate, carbofuran, and aminostigmine. With the aid of ¹H NOE pumping experiments, we were able to highlight ligand binding epitopes for the studied compounds and provide prefatory data for the ligand affinity with BSA via dissociation constant values (K_D). In addition, we demonstrate that the ¹H NOE pumping technique is suitable for the ligand competition studies solely using one NMR sample and that the technique is a simple and straightforward method capable of revealing important parameters that are used typically to define ligand-albumin interaction at the atomic level. We believe the novel precursory results herein provide important and experimentally driven data for the BSA interaction, especially for carbamate-based molecules, where the existing literature is fairly limited. Based on the preliminary experimental results, amiton and aminostigmine showed stronger binding to BSA based on NOE pumping data compared with dimethoate and carbofuran, although the obtained K_D values were observed within a similar range. Our results present the first comparable study between the organophosphorus (OP) and the carbamate (CM) toxic compounds with BSA via NMR spectroscopy only. Furthermore, the efficacy of the ¹H NOE pumping technique provided evidence that the organophosphorus and carbamate compounds bind to a common epitope site on BSA.