Fig. 2.
TMT titration experiment using the down-scaled TMT labeling strategy across laboratories. (A) Quantities and concentrations of TMTzero reagent (blue) and peptides (gray) are illustrated for increasing TMT quantities in constant labeling volumes (pep: peptide). The TMT reaction was quenched using 0.4% hydroxylamine (final concentration). (B) PSMs identifying underlabeled and fully labeled peptides are shown for intra- and interlaboratory replicates following the protocol depicted in (A). (C) The number of PSMs assigned to overlabeled, O-acylated peptides and the distribution of serine, threonine, and tyrosine in these spectra are displayed for the workflow shown in (A).