Document Detail

Diagnostic cyclisation reactions which follow phosphate transfer to carboxylate anion centres for energised [M-H](-) anions of pTyr-containing peptides.
MedLine Citation:
PMID:  21818810     Owner:  NLM     Status:  In-Data-Review    
The low-energy negative ion phosphoTyr to C-terminal -CO(2) PO(3) H(2) rearrangement occurs for energised peptide [M-H](-) anions even when there are seven amino acid residues between the pTyr and C-terminal amino acid residues. The rearranged C-terminal -CO(2) PO(2) H(O(-) ) group effects characteristic S(N) i cyclisation/cleavage reactions. The most pronounced of these involves the electrophilic central backbone carbon of the penultimate amino acid residue. This reaction is aided by the intermediacy of an H-bonded intermediate in which the nucleophilic and electrophilic reaction centres are held in proximity in order for the S(N) i cyclisation/cleavage to proceed. The ΔG(reaction) is +184 kJ mol(-1) with the barrier to the S(N) i transition state being +240 kJ mol(-1) at the HF/6-31 + G(d)//AM1 level of theory. A similar phosphate rearrangement from pTyr to side chain CO(2) (-) (of Asp or Glu) may also occur for energised peptide [M-H](-) anions. The reaction is favourable: ΔG(reaction) is -44 kJ mol(-1) with a maximum barrier of +21 kJ mol(-1) (to the initial transition state) when Asp and Tyr are adjacent. The rearranged species R(1) -Tyr-NHCH(CH(2) CO(2) PO(3) H(-) )COR(2) (R(1)  = CHO; R(2)  = OCH(3) ) may undergo an S(N) i six-centred cyclisation/cleavage reaction to form the product anion R(1) -Tyr(NH(-) ). This process has a high energy requirement [ΔG(reaction)  = +224 kJ mol(-1) , with the barrier to the S(N) i transition state being +299 kJ mol(-1) ]. Copyright © 2011 John Wiley & Sons, Ltd.
T T Nha Tran; Tianfang Wang; Sandra Hack; John H Bowie
Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Rapid communications in mass spectrometry : RCM     Volume:  25     ISSN:  1097-0231     ISO Abbreviation:  Rapid Commun. Mass Spectrom.     Publication Date:  2011 Sep 
Date Detail:
Created Date:  2011-08-05     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8802365     Medline TA:  Rapid Commun Mass Spectrom     Country:  England    
Other Details:
Languages:  eng     Pagination:  2489-99     Citation Subset:  -    
Copyright Information:
Copyright © 2011 John Wiley & Sons, Ltd.
Department of Chemistry, The University of Adelaide, South Australia, Australia, 5005.
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