Noncovalent Tagging for Identifying Unknown Contaminants of Specific Bioactivity in Environmental Water

Identifying contaminants of specific bioactivities from complicated environmental matrices remains costly and time-consuming, as it requires us to not only resolve their structures but also determine their bioactivities. Herein, a novel noncovalent tagging method is integrated in mass spectrometry for identifying unknown contaminants that target dopamine (DA) receptors. Via proteolysis of bovine serum albumin, a stereoselective hexapeptide (ACFAVE) is selected for noncovalently tagging the contaminants that possess the stereostructural characteristics of binding to DA receptors. The tagged contaminants can be readily distinguished from the coexisting species for subsequent structural analysis based on the tagging-induced shifts of the mass-to-charge ratios. Thus, both bioactivity evaluation and structure analysis are accomplished via mass spectrometry. By using this method, 1,3-diphenylguanidine (DPG), a widely used additive in rubber and plastics, is successfully identified out of 2495 features detected in the Pearl River water, with its concentration determined as only 9.8 mu g L-1. Furthermore, DPG is confirmed as a potential disrupter to the DA receptors via a simulated docking experiment, which has not been reported before. The present noncovalent tagging method provides a cost-effective and time-efficient way of identifying bioactive molecules in complicated matrices. And proteolysis of proteins is promising for developing more taggants with other desired stereoselectivities in the future.

Automated summary

This study presents a novel noncovalent tagging method integrated with mass spectrometry for identifying specific bioactive contaminants. By selecting a stereoselective hexapeptide as the tag through proteolysis, the contaminants that bind to dopamine receptors can be distinguished and analyzed using mass spectrometry. Using this method, the widely used additive 1,3-diphenylguanidine was successfully identified in Pearl River water and confirmed as a potential disrupter to dopamine receptors.