Table S4.

MS conditions used to monitor for pseudocobalamin and SAM

Compound	Transitions monitored	CE, V	CV, V
OH-pseudocobalamin	659.8 → 136.1, 348.1	30	45
CN-pseudocobalamin	673.3 → 136.1, 348.1, 660.3	30	45
Me-pseudocobalamin	668.3 → 136.1, 348.1, 660.3	30	30
Ado-pseudocobalamin	785.3 → 136.1, 348.1, 660.3	30	50
S-adenosyl methionine	399.258 → 136.1, 250.2	26	2

CE, collision energy in volts (V); CV, cone voltage in volts (V). For the pseudocobalamins, parent masses are all of the [M+2H]²⁺ except OH-pseudocobalamin, which loses its OH- during ionization as shown previously (15). 136 m/z, α ligand (adenine); 348 m/z, α ligand with sugar and phosphate groups; 660 m/z, doubly charged loss of the β ligand. Bolded transitions were used for quantification.