Fig 2. Characteristic MS/MS fragmentation of AHLs.

A) Characteristic fragments originating from the lactone ring. These fragments were used to identify AHLs in bacterial samples. Labeled masses for carbon (¹³C) and nitrogen (¹⁵N) isotopes are indicated in parenthesis. B) Characteristic fragmentation observed when no substitution is present at the third carbon of the acyl chain. C) Characteristic fragmentation observed when a 3-oxo substitution is present. In B) and C), black wavy lines indicate the bonds that are broken during fragmentation, the measured fragment is highlighted in red. D) Fragmentation spectra of selected AHL standards. Blue lines indicate peaks for characteristic fragments of the lactone ring.