Structural deviations in poly(amidoamine) dendrimers: a MALDI-TOF MS analysis

Peterson, Janek; Allikmaa, Veiko; Subbi, Juhan; Pehk, Tõnis; Lopp, Margus

doi:10.1016/s0014-3057(02)00188-x

Cited by 123 publications

(109 citation statements)

References 17 publications

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“…A spectrum showing the full assignments of the PAMAMG2OH dendrimer and defect ions is included in Supplementary Material section Figure S-1 (which can be found in the electronic version of this article). Because the abundance of the dendrimer defect species do not change with the severity of the ESI conditions and similar defects have been observed in past MALDI [30,31] and ESI [28] studies, we speculate that these defects are present in the original dendrimer samples and do not arise from the ESI process. It has been previously shown that the types of defects observed in Figure 2 result from the retro-Michael decomposition reactions that occur in the dendrimer solutions [33].…”

Section: Analysis Of Silver Ion Complexes By Esi-mssupporting

confidence: 72%

“…For example, Tolic et al utilized Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to investigate the polydispersity of PAMAM dendrimers [28], while collisional activated dissociation and ion/ion reactions were used by He and McLuckey to study the dissociation behavior of halfgeneration PAMAM dendrimers and determine the structures of imperfect dendrimer molecules [29]. MALDI-TOF mass spectrometry has also been used to determine structural deviations in PAMAM dendrimers [25,31].…”

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confidence: 99%

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Investigation of silver binding to polyamidoamine (PAMAM) dendrimers by ESI tandem mass spectrometry

Mazzitelli

Brodbelt

2006

J. Am. Soc. Mass Spectrom.

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Electrospray ionization tandem mass spectrometry (ESI-MS/MS) was used to probe the binding of silver ions and reduced silver species with polyamidoamine generation 1 amineterminated (PAMAMG1NH 2 ) and generation 2 hydroxyl-terminated (PAMAMG2OH) dendrimers. At Ag ϩ /PAMAMG2OH molar ratios of Յ1, 1:1 complexes are observed, while at ratios Ͼ1, 2:1 and low abundance 3:1 complexes emerge. Similar results were observed for PAMAMG1NH 2 . The collisional activated dissociation (CAD) patterns of the dendrimer ions are characterized by losses of amidoamine branches resulting largely from hydrogen migration and cleavage reactions. Ag ϩ /dendrimer complexes are characterized by the loss of a dendrimer branch from the complex, with the silver ion remaining bound to a dendrimer fragment. When the Ag ϩ -bound dendrimer complexes are reduced by hydrazine, low abundance complexes, whose m/z values are consistent with ones containing zerovalent silver species, are observed in the mass spectra. Complexes with three silver atoms are observed in the spectrum containing PAMAMG1NH 2 , and complexes with four and five silver atoms are observed with PAMAMG2OH. The CAD fragmentation patterns of the complexes formed after the silver reduction are different than those observed for complexes containing one silver ion and are characterized by the ejection of all silver species, possibly as a cluster, leaving the intact dendrimer ion. Experiments with Cu ϩ , Cu 2ϩ , and Pt 2ϩ binding to PAMAMG2OH were also done, but reduced metal clusters were not observed in the mass spectra after the addition of hydrazine. . In addition to numerous applications in fields such as medicine, chemistry, materials science, biology, and physics, there is interest in the use of dendrimers as templates for metal nanoparticle synthesis [3,4]. The ability to synthesize metal nanoparticles with well-defined core sizes has important implications for the study of the sizedependent photochemical, electrochemical, and optical behavior of metal clusters.Polyamidoamine (PAMAM) dendrimers [5,6] (Figure 1 [7][8][9][10][11][12]. Upon chemical reduction of the metal ion/ dendrimer complexes, the PAMAM polymer matrix encapsulates and subsequently stabilizes the metal clusters, thus preventing agglomeration [12]. These intradendrimer metal nanoparticles are soluble and have well defined sizes due to the uniform three-dimensional structure and functional group composition of the dendrimers. Interest in the formation of intradendrimer metal nanoparticles has stimulated the need for analytical methods that are capable of characterizing the dendrimer host structure and the corresponding metal/ dendrimer complexes. Electrospray ionization mass spectrometry (ESI) [13][14][15][16][17] and matrix assisted laser desorption ionization (MALDI) [18 -25] mass spectrometry have been established as powerful techniques for the analysis of dendrimer macromolecules as a result of their ability to gently transfer species from solution to the gas-phase while minimizing the fragmentation of the an...

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Section: Analysis Of Silver Ion Complexes By Esi-mssupporting

confidence: 72%

mentioning

confidence: 99%

Investigation of silver binding to polyamidoamine (PAMAM) dendrimers by ESI tandem mass spectrometry

Mazzitelli

Brodbelt

2006

J. Am. Soc. Mass Spectrom.

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“…Firstly, the proton migrates from benzylamine to the enol anion to give the benzylnitrogen anion, which attacks the 2-position carbon of pyrimidine as the nucleophile to form the Meisenheimer complex via an aromatic nucleophilic 260 addition transition-state (TS1). Secondly, the cleavage of the COO bond in the Meisenheimer complex gives rise to the RE ion via an elimination transition-state (TS2) [39,40]. Finally, the RE ion fragments into the ion at m/z 349 with a neutral loss of 6-methylenecyclohexa-2,4-dienone (MEC) through a retro-Michael transitionstate (TS3) [19,40].…”

Section: Gas Phase Reactions Of Deprotonated 1 and Related Compoundsmentioning

confidence: 99%

Using tandem mass spectrometry to predict chemical transformations of 2-pyrimidinyloxy-N-arylbenzyl amine derivatives in solution

Wang

Zhang

Guo

et al. 2006

J. Am. Soc. Mass Spectrom.

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Tandem mass spectrometry is used to predict the chemical transformations of 2-pyrimidinyloxy-N-arylbenzyl amine derivatives. Compound 1, N-2-2-4,6-dimethoxypyrimidin-2-yloxy benzylamino phenyl benzamide was selected as a model to present our idea. The CID reactions of protonated 1 include an intramolecular S N 2 reaction and a cyclodehydration reaction. Under in-source CID conditions, deprotonated 1 undergoes a Smiles rearrangement reaction and then dissociates to the ion at m/z 349. Theoretical computations were invoked to shed light on the reaction mechanisms of 1 by the semiempirical PM3 method. These studies of gas-phase reactions show the reactivity of some potential reaction centers in this molecule, which inspired us to explore the solution phase analogous reactions of 1. Further experiments show that 1 has two analogous reactions in acidic solution: the acid-catalyzed cyclodehydration reaction and the acid-catalyzed Smiles rearrangement reaction. Moreover, 1 undergoes the base-catalyzed Smiles rearrangement under basic conditions. The present study demonstrates that mass spectrometry can play an important role in predicting the chemical solution phase transformations of 2-pyrimidinyloxy-N-arylbenzyl amine derivatives. (J Am Soc Mass Spectrom 2006, 17, 253-263)

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“…[25][26][27] Finally, the RE ion fragments into the ion at m/z 349 with a neutral loss of 6-methylenecyclohexa-2,4-dienone (MEC) through a retro-Michael transition state (TS3, the energy barrier is 146.1 kJ/mol). 8,28,29 The schematic potential energy surface in the fragmentation pathway of [1-H] -is shown in Figure 5. Analysis of Figure 5 shows that the formation of the Meisenheimer complex and RE ion is favorable thermodynamically.…”

Section: Theoretical Computations Of the Main Gas-phase Fragmentationmentioning

confidence: 99%

“…25,26 Finally, the RE ion fragments into the ion at m/z 372 with a neutral loss of 6-methyl-enecyclohexa-2,4-dienone (MEC) through a retro-Michael transition state (TS3, the energy barrier is 102.6 kJ/ mol). 8,28 The ion at m/z 372 could further lose dipropylamine via a proton transfer transition state (TS4, the energy barrier is 201.0 kJ/mol) to give the fragment ion at m/z 271.…”

Section: Figurementioning

confidence: 99%

Studies of the Interesting Gas‐phase Rearrangement Reactions of 2‐Pyrimidinyloxy‐N‐arylbenzylurea Promoted by Urea‐Carbamimidic Acid Tautomerism by ESI‐MS/MS and Theoretical Computation

Xu¹,

Wang²,

Zhao³

et al. 2010

Chin. J. Chem.

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The gas-phase rearrangement reactions of compound 1, 2-dimethoxypyrimidinyloxybenzylaminobenzenedipropylurea, were studied by ESI-MS/MS. The experimental results showed that introduction of dipropylurea moiety into the molecule initiated various interesting gas-phase chemistries and the mechanisms were proposed on the basis of hydrogen/deuterium (H/D) exchange experiments and theoretical computations. Moreover, product 2, the solution-phase rearrangement product of compound 1, was synthesized and its gas-phase chemistries were also studied to support the propos gas-phase rearrangement reactions of compound 1.

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Structural deviations in poly(amidoamine) dendrimers: a MALDI-TOF MS analysis

Cited by 123 publications

References 17 publications

Investigation of silver binding to polyamidoamine (PAMAM) dendrimers by ESI tandem mass spectrometry

Investigation of silver binding to polyamidoamine (PAMAM) dendrimers by ESI tandem mass spectrometry

Using tandem mass spectrometry to predict chemical transformations of 2-pyrimidinyloxy-N-arylbenzyl amine derivatives in solution

Studies of the Interesting Gas‐phase Rearrangement Reactions of 2‐Pyrimidinyloxy‐N‐arylbenzylurea Promoted by Urea‐Carbamimidic Acid Tautomerism by ESI‐MS/MS and Theoretical Computation

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