Figure 5.

UPLC-MS chromatograms (MRM mode; acetic acid program) obtained from extracts of pea seeds that had been previously injected with a mixture of [D₅]Trp and [¹³C₆]IAA (A–C) or [D₄]4-Cl-Trp (D). On UPLC, the RT of a deuterated species is earlier than the RT for the endogenous species; ¹³C-labeled species have the same RT as their endogenous counterparts (on the UPLC-MS system used, within 0.01 min). A, IAA became enriched with D₅ label (middle channel; RT = 4.08) after injection of [D₅]Trp; the endogenous IAA (bottom channel; RT = 4.11) and the injected [¹³C₆]IAA (top channel; RT = 4.10) were also detected. B, 4-Cl-IAA also became enriched with D₄ label (middle channel; RT = 4.89) from the injected [D₅]Trp (one deuterium is replaced with a chlorine atom), but the ¹³C₆ label from the injected [¹³C₆]IAA was not incorporated into 4-Cl-IAA (top channel; the peaks observed in this channel did not have the correct RT for [¹³C₆]4-Cl-IAA). C, 4-Cl-Trp became enriched with D₄ label (top channel; RT = 2.18) from the injected [D₅]Trp. D, In a separate experiment, 4-Cl-IAA became enriched with deuterium label (top two channels) after deuterated 4-Cl-Trp was injected; endogenous 4-Cl-IAA was also detected (bottom channel). The [D₄]4-Cl-IAA signal detected in this experiment contained a small contribution from [³⁷Cl,D₂]4-Cl-IAA.