Mechanism of action of thimerosal best described as:

• A. Irreversibly bind to the phospholipids and proteins of the membrane, thereby impairing permeability
• B. Causes cell membrane disruption and denaturation of bacterial proteins
• C. Precipitation of proteins and oxidation of sulfhydryl groups
• D. Crosslinking of macromolecules

Answer: (C)

Thimerosal works by releasing mercury ions that have a high affinity for sulfhydryl (-SH) groups in proteins. Binding to these thiol groups disrupts protein structure and enzyme function, leading to protein precipitation and loss of activity. Oxidation of sulfhydryl groups further contributes to protein inactivation. This specific interaction with thiol groups explains why the mechanism is best described as precipitation of proteins and oxidation of sulfhydryl groups. Other options describe actions more typical of membrane disruption or crosslinking agents, which aren’t how thimerosal primarily acts.