Wyniki wyszukiwania - Biblioteka Nauki

Nowa wersja platformy, zawierająca wyłącznie zasoby pełnotekstowe, jest już dostępna.
Przejdź na https://bibliotekanauki.pl

Ograniczanie wyników

Znaleziono wyników: 3

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: fragmentation pathways

Sortuj według:

Ogranicz wyniki do:

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

100%

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

Open Chemistry

2006

tom 4

nr 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.

Open Chemistry

2007

tom 5

nr 1

316-329

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.

Electron Ionization Mass Spectrometric study of 5-Benzylidene Rhodanines Differentially Substituted in the Phenyl Ring and 3-Phrnyl Rhodanine

100%

Frański R. , Schroeder G. , Shendrik A.

Polish Journal of Chemistry

2005

tom Vol. 79 / nr 8

1285-1293

The electron ionization behaviour of 5-benzylidene rhodanines (1-10) and 3-phenyl rhodanine (11) was studied. For each of the 1-10 an efficient loss of mass 87, namely the loss of HNCS and CO molecules, was observed. The compounds containing a hydroxy group at the ortho position to the rhodanine moiety showed also an abundant fragment ion formed by the loss of HNCS. The other phenyl ring substituents did not affect this fragmentation pathway. On the other hand, decomposition of the [M-87]+ _ fragment ion strongly depends on the phenyl ring substitution, e.g. for 5 having a methoxy group at the meta position to the rhodanine moiety, in contrast to its ortho and para correspondents 4 and 6, the loss of the fragments HCO. and H2CO proceeded. 3-Phenyl rhodanine lost the ketene molecule yielding the fragment ion of m/z 167. On the grounds of its decomposition and comparison with reference compound decomposition it was deduced that this ion had the structure of 2-mercaptobenzothiazole.