Fragmentation of poly(amidoamine) dendrimers in matrix-assisted laser desorption

Identification and quantification of poly(amidoamine) PAMAM dendrimers of generations 0 to 3 by liquid chromatography/hybrid quadrupole time‐of‐flight mass spectrometry in aqueous medium

“…As the production of PAMAMs is based on divergent synthesis, the most probable fragmentation pathway was via a retro‐Michael reaction. Most of the investigations on structure defects or metal/ion complexes that were carried out using a unit mass resolution spectrometer in full scan and MS/MS modes proposed that the dendrimer precursor ions fragmented via retro‐Michael reactions, in both positive and negative ionization mode . He and McLuckey demonstrated that ion/ion proton transfer reactions facilitated the interpretation of the product ion mass spectra of PAMAM generation 0.5, through manipulation of the charge states of the PAMAM precursor ions to form lower charge states than those initially formed by ESI.…”

“…Most of the investigations on structure defects or metal/ion complexes that were carried out using a unit mass resolution spectrometer in full scan and MS/MS modes proposed that the dendrimer precursor ions fragmented via retro-Michael reactions, in both positive and negative ionization mode. [19,20,23,[33][34][35][36] He and McLuckey [23] demonstrated that ion/ion proton transfer reactions facilitated the interpretation of the product ion mass spectra of PAMAM generation 0.5, through manipulation of the charge states of the PAMAM precursor ions to form lower charge states than those initially formed by ESI. Work by Mazzitelli and Brodbelt [27] has shown that the ESI-MS/MS fragmentation pattern of the PAMAM G1-silver complex results from hydrogen migration and cleavage reactions at the most exterior tertiary amine to produce a loss of 114 Da that could be could be rationalized as retro-Michael decomposition reactions.…”

Off‐line capillary electrophoresis/matrix‐assisted laser desorption/ionization tandem time‐of‐flight mass spectrometry for analysis of synthesized poly(amido)amine dendrimers

“…[4] Until now, the structural characterization of PAMAMs has generally been performed using size-exclusion chromatography (SEC), [5] hydrophilic interaction (HILIC) [6] or reversed-phase (RP) [7,8] high-performance liquid chromatography (HPLC), capillary zone electrophoresis (CZE), [9][10][11][12][13] nuclear magnetic resonance [1,14,15] ( 1 H, 2 H, 13 C NMR) and mass spectrometry (MS). [1,6,[16][17][18][19][20][21] In particular, electrospray ionization (ESI) [16,18,19] and matrix-assisted laser desorption/ ionization (MALDI) [6,17,20] MS appeared to be valuable tools for the structural analysis of these compounds. The PAMAMs are prepared using well-established synthetic procedures, [1] although side reactions can lead to defect contamination as previously described.…”

“…External calibration of MALDI-TOF mass spectra was carried out using singly charged [M + H] + monoisotopic peaks of angiotensin II (10 pmol/mL), substance P (10 pmol/mL) and ACTH 18-39 fragment (5 pmol/mL). Two matrices were tested: the 'hot' [17] a-cyano-4-hydroxycinnamic acid (CHCA) prepared in acetonitrile/methanol (50:50, v/v) at a concentration of 10 mg/mL and the 'colder' [17] 2,5-dihydroxybenzoic acid (DHB) prepared in 0.1% aqueous trifluoroacetic acid/acetonitrile (70:30, v/v) to a concentration of 10 mg/mL. In both cases, duplicates of MALDI spots were prepared for each collected fraction using a dried-droplet-based method including pre-spotting with matrix; 0.5 mL of matrix solution was first applied to the stainless-steel target plate (Bruker), dried under vacuum, covered by 0.5 mL of a mixture prepared by mixing 0.5 mL of the CZE-collected fraction solution with 0.5 mL of matrix solution, and then dried under vaccum.…”

“…The [G1 EDA + Na] + precursor ion (m/z 1452.4) for the ideally branched EDA-cored G1 PAMAM ( Fig. 3(A)) underwent the characteristic fragmentations [17,19,22] of a full-generation PAMAM including the well-described successive neutral loss of either a branch (114 Da) or a CH 2 = CH(OH)NH(CH 2 ) 2 NH 2 molecule (102 Da, less abundant than the loss of 114 Da) as well as the elimination of an arm (342 Da which could arise from a retro-Michael rearrangement [18,19] ). The corresponding product ions were detected at m/z 1338.4, 1350.4 and 1110.2 (Scheme 1(A)).…”