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Sequencing peptides by electrospray ion-trap mass spectrometry: A useful tool in synthesis of Axinastatin 3

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Jia C., Qi W., He Z., Qiao B.

Open Chemistry

2006

vol. 4

issue 4

620-631

Axinastatin 3 as a potential anticancer agent was synthesized by chemical methods. In an electrospray ion-trap mass spectrometer, using one stage of tandem mass spectrometry (MS/MS), the linear peptide intermediate was sequenced via the complementarities of y and b ions. Then, using multistep MS/MS (to MS6), the cyclic peptide was sequenced through sequentially removing one amino acid residue in each stage of MS/MS. The difference of the fragmentation mechanisms and the sequencing approaches between them is discussed.

Electrospray ionization mass spectrometric study of mercury complexes of N-heterocyclic carbenes derived from 1,2,4-triazolium salt precursors

100%

Frański R., Gierczyk B., Schroeder G., Pieper S., Springer A., Linscheid M.

By mixing 1,2,4-triazolium salts (precursors of N-heterocyclic carbenes 1–6) with mercury acetate, a number of complexes have been obtained under electrospray ionization condition. Carbenes 1 and 2 contain one carbene center; therefore, they are able to bond only one mercury cation. Carbenes 3–5 contain two carbene centers; therefore, they can bond two mercury cations. Mercury complexes of 1–5 always contain an acetate anion attached to a mercury cation. Carbene 6 also contains two carbene centers; however, its structure allows formation of a complex containing mercury bonded simultaneously to both centers, therefore, the complex that does not contain an acetate anion. The MS/MS spectra taken for complexes of carbenes 1–5 have shown formation of a cation corresponding to N1 substituent (adamantyl or benzyl), and those of complexes of carbenes 3–5 (doubly charged ions) have also shown the respective complementary partner ions. Mercury complex of 2 has yielded some other interesting fragmentation pathways, e.g. a loss of the HHgOOCCH3 molecule. The fragmentation pathway of the mercury complexes of 6 was found to be complicated.

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2 Open Chemistry

1 2007

1 2006

1 Frański R.

1 Gierczyk B.

1 He Z.

1 Jia C.

1 Linscheid M.

1 Pieper S.

1 Qi W.

1 Qiao B.

1 Schroeder G.

1 Springer A.

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Sequencing peptides by electrospray ion-trap mass spectrometry: A useful tool in synthesis of Axinastatin 3

Electrospray ionization mass spectrometric study of mercury complexes of N-heterocyclic carbenes derived from 1,2,4-triazolium salt precursors