11. Substituting thiols or water for the copper salts generates thioethers or phenols, respectively. 12. Thioethers are typically prepared by alkylation of thiols . 13. It is trapped therein by reduction back to ascorbate by glutathione and other thiols . 14. The reduction occurs via direct electron transfer primarily from ascorbate and some nonprotein thiols . 15. Disulfides reduce to thiols ( via thiolates ). 16. It is also fastidious and difficult to culture, requiring the presence of thiols . 17. In the absence of thiols , selenols tend to overoxidize to produce seleninic acids. 18. In larger concentrations, thiols are toxic. 19. Antioxidants such as thiols or ascorbic acid ( vitamin C ) terminate these chain reactions. 20. Furthermore, it is often not needed to remove TCEP before modification of protein thiols .
