Document Detail

Stereoselectivity in the collision-activated reactions of gas phase salt complexes.
MedLine Citation:
PMID:  15465364     Owner:  NLM     Status:  MEDLINE    
The collision-activated dissociations (CAD) of gas phase salt complexes composed of chiral ions were studied in a quadrupole ion trap mass spectrometer. Because both partners in the salt are chiral, diastereomeric complexes can be formed (e.g., RR, RS). Two general types of complexes were investigated. In the first, the complex was composed of deprotonated binaphthol and a chiral bis-tetraalkylammonium dication. CAD of these complexes leads to the transfer of a proton or an alkyl cation to the binaphtholate leading to a singly-charged tetraalkylammonium cation. During CAD, diastereomeric complexes give significantly different product distributions indicating reasonable stereoselectivity in the process. In the second system, the complexes involved a peptide dianion and a chiral tetraalkylammonium cation. These systems may be viewed as very simple models for the interactions of peptides/proteins with small chiral molecules. Again, stereoselectivity was evident during CAD, but the extent was dependent on the nature of the peptide and not observable in some cases. To better understand the structural features needed to achieve stereoselectivity in gas phase salt complexes, representative transition states were modeled computationally. The results suggest that it is critical for the asymmetry of the nucleophile (i.e., anion) to be well represented in the vicinity of its reactive center.
Scott Gronert; Adelaide E Fagin; Keiko Okamoto
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Journal of the American Society for Mass Spectrometry     Volume:  15     ISSN:  1044-0305     ISO Abbreviation:  J. Am. Soc. Mass Spectrom.     Publication Date:  2004 Oct 
Date Detail:
Created Date:  2004-10-06     Completed Date:  2005-09-30     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  9010412     Medline TA:  J Am Soc Mass Spectrom     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1509-16     Citation Subset:  IM    
Department of Chemistry and Biochemistry, San Francisco State University, California 94132, USA.
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MeSH Terms
Alanine / chemistry
Amino Acid Sequence
Gases / chemistry*
Models, Molecular
Peptides / chemistry
Salts / chemistry*
Substrate Specificity
Grant Support
Reg. No./Substance:
0/Gases; 0/Ions; 0/Peptides; 0/Salts; 56-41-7/Alanine

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