HPLC analysis of cultures supplemented with caffeic acid or ferulic acid. E. coli expressing 4CL1 and STS was supplemented with 1 mM substrate and grown in modified M9 medium at 30°C for 24 hrs prior to extraction. Panel A: Production of piceatannol from caffeic acid. Upper chromatogram shows extracted E. coli culture, bottom chromatogram shows piceatannol standard run under identical HPLC conditions. At right are the UV spectra for both recombinant piceatannol (1) (m/z 243.1) and piceatannol standard (2) (m/z 243.1). Peak 3 is residual caffeic acid (m/z 179.2). Panel B: E. coli expressing 4CL1 and STS supplemented with ferulic acid. Peak 1 corresponds to residual ferulic acid (m/z 193.1). Peak 2 corresponds to the ferulic acid derived tetraketide lactone (m/z 301.1) and peak 3 is the corresponding triketide lactone (m/z 259.1).