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13 C NMR study of the ion‐binding selectivity of a new ammonium ionophore
Author(s) -
McGimpsey W. Grant,
Soto Ernesto,
Driscoll Peter F.,
Nowak Cheryl,
Benco John S.,
Cooper Christopher G. F.,
Lambert Christopher R.
Publication year - 2008
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.2287
Subject(s) - chemistry , ionophore , selectivity , ammonium , ion , carbon 13 nmr , proton nmr , bicyclic molecule , resonance (particle physics) , potassium , sodium , chemical shift , inorganic chemistry , crystallography , stereochemistry , organic chemistry , calcium , physics , particle physics , catalysis
A bicyclic peptide, cyclo ( L ‐Glu 1 — D ‐Leu 2 —Aib 3 — L ‐Lys 4 — D ‐Leu 5 — D ‐Ala 6 )‐cyclo‐(1γ‐4ε) (I), was designed and synthesized to provide an ammonium ion complexation site in a tetrahedral geometry. Molecular modeling, dynamics and electrostatic studies for I indicated that it exhibits some selectivity for ammonium ions over potassium and sodium ions. NMR measurements in CDCl 3 /CD 3 OD (1:1) show that for those carbonyl groups involved in cation binding, 13 C resonances shifted downfield with increasing cation concentration. The resonance that exhibited the largest change in chemical shift between uncomplexed and complexed forms was used to determine the selectivity. Selectivity values obtained were log K NH 4 + , Na += − 2.4 and log K NH 4 + , K += − 0.6. Copyright © 2008 John Wiley & Sons, Ltd.