title: Electrospray ionization mass spectrometric studies on the characteristic fragmentation of Asp/cyclen conjugates.
abstract: BACKGROUND
  Differentiation and structural characterization of Asp/cyclen conjugates by electrospray ionization tandem mass spectrometry (ESI-MS(n)) are significantly important for their biomedical application. Hence, the present study is conducted.
  
  
  METHODS
  The fragmentations of Asp/cyclen conjugates generated by positive ion mode electrospray ionization were examined here by low-energy collision-induced dissociation (CID). ESI-MS(n) spectra of cyclen were acquired to confirm cyclen contraction products derived from the studied compounds. The fragments derived from the Asp/cyclen conjugates were proved by deuterium-exchange experiments.
  
  
  RESULTS
  Asp/cyclen conjugates displayed characteristic dissociation pathways, including cleavages of amide bonds, loss of NH3 and cyclen contraction pathways. It was observed that cleavages of C-terminal amide bonds generated b2 and b2  + H2O ions from the protonated CyclenAspAspAsp and a b1  + H2O ion from the protonated CyclenAspAsp. In addition, various cyclen contraction products were also observed.
  
  
  CONCLUSIONS
  In ESI-MS(n) spectra of studied compounds, fragments of bn-1  + H2O or cyclic anhydride were generated due to facile mobilization of C-terminal or side-chain COOH protons. In addition, the cyclen contraction products were detected. These results might provide sufficient information for the identification of Asp/cyclen conjugates by mass spectrometry.
authors: State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing, 100029, P. R. China.
authors: Chunying
authors: C
authors: Ma
authors: Chao
authors: C
authors: Li
authors: Xingrong
authors: X
authors: Luan
authors: Jin
authors: J
authors: Zhang
authors: Renzhong
authors: R
authors: Qiao
authors: Yufen
authors: Y
authors: Zhao
mesh_terms: D000577:Amides / Q000737:chemistry; D001224:Aspartic Acid / Q000737:chemistry*; D000080027:Cyclams; D006571:Heterocyclic Compounds / Q000737:chemistry*; D007477:Ions / Q000737:chemistry; D008958:Models, Molecular; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods
chemical_list: D000577:Amides; D000080027:Cyclams; D006571:Heterocyclic Compounds; D007477:Ions; D001224:Aspartic Acid; C038072:cyclen