D Figures 2 and three. In Supof compounds 3ad and 6ad are and 6a-d in

D Figures 2 and three. In Supof compounds 3ad and 6ad are and 6a-d in presented in three. In Supplementary Inplementary Information (SI), we present the fragmentation spectra for all obtained their formation (SI), we present the fragmentation spectra for all obtained peptides and peptides and their derivatized analogues (Figures S1 70). For the tandem mass experiments derivatized analogues (Figures S1 70). For every single compound, each compound, the tandem mass recorded in differentrecorded energies. It was D-Glutamic acid Description identified energies. It wasabundances and had been experiments have been collision in distinctive collision that the relative found that the relative abundances and numbers on the observed and identified fragment ions changed numbers from the observed and identified fragment ions changed together with the collisional energy. The the collisional study revealed a series of study revealed b ions of derivatized anawithfragmentation power. The fragmentation Mirdametinib site intensive a in addition to a seriesfor intensive a and b logues derivatized analogues formed in CID experiments. The observed results correlate ions forformed in CID experiments. The observed outcomes correlate well together with the literature information described for other information described for other quaternary ammonium [13] and phoswell with all the literature quaternary ammonium [13] and phosphonium derivatives [18] at the same time as for derivatives [18] also as for compounds [22]. The relative phonium compounds containing the 2,4,6-triphenylpyridinium moiety containing the abundance of the precursor ion peak varies relative abundance on the precursor ion indi2,4,6-triphenylpyridinium moiety [22]. Thewildly from spectrum to spectrum, whichpeak cates wildly from spectrum to spectrum, which indicates that a lot of with the fragments variesthat quite a few on the fragments (e.g., all a-type ions) come from secondary fragmentation. However, this ions) come from secondary fragmentation. Even so, this does not impair (e.g., all a-type will not impair the validity of our conclusions with regards to the stability of QAS or the of our conclusions relating to the The signals inside the fragmentation around the for the validity influence around the observed effects. stability of QAS or the influence spectra obderivatized analogues containing fragmentation spectra sequence are also accompanied served effects. The signals in theArg, Asp, and Thr in thefor derivatized analogues conby standard neutral losses such as sequence are also accompanied by standard neutral losses taining Arg, Asp, and Thr inside the a water molecule [M8.011], ammonia [M7.027], and an acetaldehyde molecule [M4.026] (Figures two and 3). Additionally, acetaldehyde molesuch as a water molecule [M8.011], ammonia [M7.027], and anfragmentation from the side chain of Thr and loss and 3). In addition, fragmentation in the previously described cule [M4.026] (Figures 2of the neutral molecule of 44.026 Da was side chain of Thr and by Wang et al. [30], which may well 44.026 Da was previously described sodium et al. [30], loss in the neutral molecule of happen in both protonated peptides andby Wangadducts. Moreover, inside the case each protonated peptides and sodium adducts. ion corresponding which may perhaps take place in of N,N,N-triethylammoniumacetyl derivatives, anIn addition, within the to a of N,N,N-triethylammoniumacetyl derivatives, an which indicates the a mass loss case mass loss of 28.031 was noted (Figures 2a and 3a),ion corresponding to elimination of 28.031 was noted (Figures 2a and N,N,N-triethylammonium group that seems as a of one alkene (-C2 H4) group from the.