Rxi 5 sil column

AAP-b2 was methylated and then hydrolyzed in 1 mL of trifluoroacetic acid (TFA, 2 mol/L) at 110 °C for 1.5 h [39 (link)]. The excess TFA in hydrolysate was removed by evaporation under reduced pressure. The dry residues were reduced using 60 mg of sodium borohydride for 8 h and acetic acid was added to neutralize the solution. Afterwards, acetic anhydride was added and the reaction was kept at 100 °C for 1 h. Toluene was added to remove the excess acetic anhydride. The resulting product was redissolved in trichloromethane, washed with ultrapure water and evaporated by rotation. Finally, the product was dissolved in trichloromethane and analyzed using a gas chromatography-mass spectrometry system (GC-MS, QP2010, Shimadzu, Kyoto, Japan) equipped with a RXI-5 SIL column (30 m × 0.25 mm × 0.25 mm). The temperature was increased from 120 °C to 250 °C at a rate of 3 °C/min and maintained for 5 min. The carrier gas was helium, and the flow rate was 1 mL/min.

The analysis of terpene products (C₁₀–C₂₅) was performed as described previously (Falara et al., 2011). Briefly, 1 μl of sample was autoinjected into a Shimadzu QP‐2010 SE GC‐MS system equipped with a Rxi‐5Sil column (30 m length, 0.25 mm i.d., and 0.25 μm film thickness; Restek, Bellefonte, PA, USA). Analysis of isoprene was performed by directly injecting the SPME fibre into the Shimadzu QP‐2010 SE GC‐MS system equipped with the Rxi‐5Sil column. The analysis of prenyltransferase assay products was performed using an EC‐WAX column (30 m length, 0.32 mm i.d., and 0.25 μm film thickness; Grace, Columbia, MD, USA). The identification methods for each terpene compound are listed in Table S2. Details of GC–MS parameters can be found in Methods S1.