Possible regulatory role in biology of trimethylamineN-oxide and aromatic N-oxides: formation of disulphide bonds

Substituted thiophenol + trimethylamine N-oxide (TMAO) systems and substituted thiophenol + aromatic N-oxide systems were studied by FT-IR and 1H NMR spectroscopy. In the thiophenol + TMAO systems strong SH…ONS− …H+ON hydrogen bonds with large proton polarizability are formed. The life time of these hydrogen bonds is, however, limited because finally disulphide bonds are formed. In this reaction water and trimethylamine are also formed. With aromatic N-oxides neither hydrogen bond formation nor other interactions are observed. Hence the disulphide bond formation does not occur either. The results obtained with these studies suggest that the reaction between SH groups and TMAO may be of great significance for the formation of disulphide bonds in biology because TMAO is present in plant and animal cells.