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Electron capture dissociation and collision-induced dissociation of metal ion (Ag(+), Cu(2+), Zn(2+), Fe(2+), and Fe(3+)) complexes of polyamidoamine (PAMAM) dendrimers.

Kaczorowska MA, Cooper HJ - J. Am. Soc. Mass Spectrom. (2008)

Bottom Line: Complexes were of the form [PD + M + mH](5+) where PD = generation two PAMAM dendrimer with amidoethanol surface groups, M = metal ion, m = 2-4.The results suggest that complexes of Fe(3+) and Cu(2+) are coordinated via both core tertiary amines, whereas coordination of Ag(+) involves a single core tertiary amine.The Zn(2+) and Fe(2+) complexes do not appear to involve coordination by the dendrimer core.

View Article: PubMed Central - PubMed

Affiliation: School of Biosciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom.

ABSTRACT
The electron capture dissociation (ECD) and collision-induced dissociation (CID) of complexes of polyamidoamine (PAMAM) dendrimers with metal ions Ag(+), Cu(2+), Zn(2+), Fe(2+), and Fe(3+) were determined by Fourier transform ion cyclotron resonance mass spectrometry. Complexes were of the form [PD + M + mH](5+) where PD = generation two PAMAM dendrimer with amidoethanol surface groups, M = metal ion, m = 2-4. Complementary information regarding the site and coordination chemistry of the metal ions can be obtained from the two techniques. The results suggest that complexes of Fe(3+) and Cu(2+) are coordinated via both core tertiary amines, whereas coordination of Ag(+) involves a single core tertiary amine. The Zn(2+) and Fe(2+) complexes do not appear to involve coordination by the dendrimer core.

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ECD FT-ICR mass spectrum of (a) [PD + Cu2+ + 3H]5+ ions and (b) [PD + Fe3+ + 2H]5+ ions. PD = PAMAM dendrimer. K cleavages are marked in red; a/x cleavages are marked in blue.
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fig1: ECD FT-ICR mass spectrum of (a) [PD + Cu2+ + 3H]5+ ions and (b) [PD + Fe3+ + 2H]5+ ions. PD = PAMAM dendrimer. K cleavages are marked in red; a/x cleavages are marked in blue.

Mentions: As described above, the ECD of protonated PAMAM dendrimers has been determined previously [21]. The dominant fragmentation channel for ECD of protonated PAMAM dendrimers is cleavage at the tertiary amines in the interior of the dendrimer. Pronounced amide bond cleavage in the interior of the dendrimer is also observed. Typically, the charge-reduced species [M + nH](n −1)+· constitutes a minor peak. The ECD MS/MS spectrum of [PD + Cu2+ + 3H]5+ is shown in Figure 1a and the fragments are detailed in Supplementary Table 1. The results suggest that electron capture occurs either by the metal ion or by the dendrimer ligand. The base peak in this mass spectrum can be assigned to the charge-reduced complex, [PD + Cu+ + 3H]4+, formed as a result of electron capture by the divalent copper ion. A series of peaks corresponding to fragment ions that arise from dissociation of this charge-reduced complex were also observed. For example, fragments formed as a result of cleavage within generation G0 of the dendrimer ligand, [PD + Cu+ − G0(Kout) + H]2+ and [PD + Cu+ − G0(x) + H]2+, were found. Fragments containing Cu+ that resulted from cleavage in generation G1 were also apparent. No Cu+-containing fragments from generation G2 were observed. All of the Cu+-containing fragments derived from cleavages surface-side of the tertiary amines (K cleavages, marked red on the mass spectrum) or core-side of the amide (a/x cleavage, marked blue on the mass spectrum). Those cleavages are minor or non-existent in the ECD of protonated dendrimers. A series of fragment ions containing Cu2+, e.g., [PD + Cu2+ − G1(out)]2+ and [PD + Cu2+ − G1(out) + H]3+, was also observed. Presumably, those fragments were the result of electron capture by the dendrimer ligand. The presence of Cu2+-containing fragments resulting from cleavage surface-side of the tertiary amines (K cleavages), e.g., [PD + Cu2+ − G2(Kout) + H]3+ and [PD + Cu2+ − G2(Kout)]2+, demonstrates the influence of the metal ion on fragmentation behavior: those cleavages are rare in the ECD of protonated PAMAM dendrimer ions. In addition, nonmetal-containing fragments resulting from cleavage at tertiary amine or amide bonds were observed. It is not possible to say whether these fragments are the result of electron capture by the metal or ligand, however, as they reflect the patterns observed for protonated species, we speculate they arise following electron capture by the ligand. The following fragments fall within this category: G1(out)+, G0(out)+, Gcore(out)+, Gcore(in)+, G1(y)+ and G0(y)+. For comparison, the ECD mass spectrum of [PD + Cu2+ + 2H]4+ is shown in Supplemental Figure 1. Cu+-containing fragments deriving from cleavage surface-side of the tertiary amines (K cleavage) and core-side of the amide (a/x cleavage), and Cu2+-containing fragments deriving from K cleavage are observed.


Electron capture dissociation and collision-induced dissociation of metal ion (Ag(+), Cu(2+), Zn(2+), Fe(2+), and Fe(3+)) complexes of polyamidoamine (PAMAM) dendrimers.

Kaczorowska MA, Cooper HJ - J. Am. Soc. Mass Spectrom. (2008)

ECD FT-ICR mass spectrum of (a) [PD + Cu2+ + 3H]5+ ions and (b) [PD + Fe3+ + 2H]5+ ions. PD = PAMAM dendrimer. K cleavages are marked in red; a/x cleavages are marked in blue.
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Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC2667233&req=5

fig1: ECD FT-ICR mass spectrum of (a) [PD + Cu2+ + 3H]5+ ions and (b) [PD + Fe3+ + 2H]5+ ions. PD = PAMAM dendrimer. K cleavages are marked in red; a/x cleavages are marked in blue.
Mentions: As described above, the ECD of protonated PAMAM dendrimers has been determined previously [21]. The dominant fragmentation channel for ECD of protonated PAMAM dendrimers is cleavage at the tertiary amines in the interior of the dendrimer. Pronounced amide bond cleavage in the interior of the dendrimer is also observed. Typically, the charge-reduced species [M + nH](n −1)+· constitutes a minor peak. The ECD MS/MS spectrum of [PD + Cu2+ + 3H]5+ is shown in Figure 1a and the fragments are detailed in Supplementary Table 1. The results suggest that electron capture occurs either by the metal ion or by the dendrimer ligand. The base peak in this mass spectrum can be assigned to the charge-reduced complex, [PD + Cu+ + 3H]4+, formed as a result of electron capture by the divalent copper ion. A series of peaks corresponding to fragment ions that arise from dissociation of this charge-reduced complex were also observed. For example, fragments formed as a result of cleavage within generation G0 of the dendrimer ligand, [PD + Cu+ − G0(Kout) + H]2+ and [PD + Cu+ − G0(x) + H]2+, were found. Fragments containing Cu+ that resulted from cleavage in generation G1 were also apparent. No Cu+-containing fragments from generation G2 were observed. All of the Cu+-containing fragments derived from cleavages surface-side of the tertiary amines (K cleavages, marked red on the mass spectrum) or core-side of the amide (a/x cleavage, marked blue on the mass spectrum). Those cleavages are minor or non-existent in the ECD of protonated dendrimers. A series of fragment ions containing Cu2+, e.g., [PD + Cu2+ − G1(out)]2+ and [PD + Cu2+ − G1(out) + H]3+, was also observed. Presumably, those fragments were the result of electron capture by the dendrimer ligand. The presence of Cu2+-containing fragments resulting from cleavage surface-side of the tertiary amines (K cleavages), e.g., [PD + Cu2+ − G2(Kout) + H]3+ and [PD + Cu2+ − G2(Kout)]2+, demonstrates the influence of the metal ion on fragmentation behavior: those cleavages are rare in the ECD of protonated PAMAM dendrimer ions. In addition, nonmetal-containing fragments resulting from cleavage at tertiary amine or amide bonds were observed. It is not possible to say whether these fragments are the result of electron capture by the metal or ligand, however, as they reflect the patterns observed for protonated species, we speculate they arise following electron capture by the ligand. The following fragments fall within this category: G1(out)+, G0(out)+, Gcore(out)+, Gcore(in)+, G1(y)+ and G0(y)+. For comparison, the ECD mass spectrum of [PD + Cu2+ + 2H]4+ is shown in Supplemental Figure 1. Cu+-containing fragments deriving from cleavage surface-side of the tertiary amines (K cleavage) and core-side of the amide (a/x cleavage), and Cu2+-containing fragments deriving from K cleavage are observed.

Bottom Line: Complexes were of the form [PD + M + mH](5+) where PD = generation two PAMAM dendrimer with amidoethanol surface groups, M = metal ion, m = 2-4.The results suggest that complexes of Fe(3+) and Cu(2+) are coordinated via both core tertiary amines, whereas coordination of Ag(+) involves a single core tertiary amine.The Zn(2+) and Fe(2+) complexes do not appear to involve coordination by the dendrimer core.

View Article: PubMed Central - PubMed

Affiliation: School of Biosciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom.

ABSTRACT
The electron capture dissociation (ECD) and collision-induced dissociation (CID) of complexes of polyamidoamine (PAMAM) dendrimers with metal ions Ag(+), Cu(2+), Zn(2+), Fe(2+), and Fe(3+) were determined by Fourier transform ion cyclotron resonance mass spectrometry. Complexes were of the form [PD + M + mH](5+) where PD = generation two PAMAM dendrimer with amidoethanol surface groups, M = metal ion, m = 2-4. Complementary information regarding the site and coordination chemistry of the metal ions can be obtained from the two techniques. The results suggest that complexes of Fe(3+) and Cu(2+) are coordinated via both core tertiary amines, whereas coordination of Ag(+) involves a single core tertiary amine. The Zn(2+) and Fe(2+) complexes do not appear to involve coordination by the dendrimer core.

Show MeSH
Related in: MedlinePlus