Tandem mass spectrometric investigation of acylpolyamines of spider venoms and their ¹⁵N-labeled derivatives

Abstract

The fragmentation mechanism of the acylpentamine toxins 1-4 found in the venom of the spider Agelenopsis aperta has been investigated in detail. To identify the origin of the two doublets of unexpected fragment ions at m/z 129/112 and m/z 115/98, three synthetic 15N-labeled analogs 5-7 have been prepared and subjected to CID fragmentation on a triple quadrupole mass spectrometer. It appears that the unexpected doublet of fragment ions arises from an internal portion of the polyamine backbone after either a transaminative Zip reaction or a sequential fragmentation of the quasi-molecular ion. The second option has been proven by in-source CID experiments. The detailed knowledge of acylpentamine fragmentation mechanisms is essential for the correct characterization of isomeric compounds, particularly for coeluting compounds within complex mixtures such as spider venoms.

Structure Elucidation of Polyamine Toxins in the Venom of the Spider Larinioides folium

“…4. Application of the fragmentation rules elaborated earlier [6,7] suggested the polyamine backbone PA3(1)43 for the compound, also shown in Fig. 4.…”

A Template Approach for the Characterization of Linear Polyamines and Derivatives in Spider Venom

“…For instance, the four isomeric spider toxins IndAc3334, IndAc3343, IndAc3433, and IndAc4333 (AG416a, AG416, AG416c and AG416b) discussed earlier 23,24 (see also Figure 1S in the Supplementary Material), have finally been identified on the basis of such unique patterns. The compounds differ solely in the location of the diaminobutane moiety within the pentamine backbones, but their spectra are quite different.…”

“…The predominant fragmentation reaction observed with polyamine backbones is the intramolecular nucleophilic substitution of a protonated amino or guanidino group as revealed by several studies performed by us [21][22][23][24] and by others 27,28 with synthetic reference compounds, isotope labeling and MO calculations (Scheme 1). These reactions lead, in the case of simple polyamine frameworks of the type A, to the formation of a charged cyclic structure such as B by loss of an uncharged amine such as C. Since the nucleophilic substitution can occur at each diaminoalkane moiety of the polyamine backbone and, for a given diaminoalkane moiety, likewise "from the left to right" (full-lined arrows) or "from the right to left" (dashed-lined arrows), the chain of the polyamine moiety can virtually be walked along, starting from both sides of the molecule.…”

“…These are formed by neutral loss of [z n -H] portions, possibly through H + transfer in intermediary proton-bound complexes. 24 These truncated ions lead to z¢ and y¢ ions by intramolecular substitutions as described for the [M + H] + precursor ions. As an example, the complete interpretation of the CID spectrum of IndAc3334 23 is shown in Figure 1.…”

“…We have contributed to the topic by investigating the toxins of several spider species, undertaking, in particular, in-depth studies of the fragmentation fate of such compounds upon collision-induced dissociation (CID). 16,[21][22][23][24][25][26] These studies have resulted in a collection of data that now allow the straightforward structural elucidation of unknown polyamine derivatives by the application of some rather simple fragmentation rules or by direct comparison of analyte MS/MS with spectral templates obtained from reference compounds.…”