Dickins, R. S. and Batsanov, A. S. and Howard, J. A. K. and Parker, D. and Puschmann, H. and Salamano, S. (2004) 'Structural and NMR investigations of the ternary adducts of twenty alpha-amino acids and selected dipeptides with a chiral, diaqua-ytterbium complex.', Dalton transactions. (1). pp. 70-80.
A detailed investigation of the nature of the binding of each of the 20 common alpha-amino acids and various selected dipeptides to a chiral, diaqua-ytterbium complex in aqueous solution has been carried out. Analysis of the dipolar H-1 NMR paramagnetic shifts suggests that the alpha-amino acids form a common chelated structure within a nine-coordinate mono-capped square antiprismatic coordination environment, with the amine N axially disposed. Crystal structures of nine chelated YbL1-amino acid adducts (Gly, Ala, Ser, Thr, Met) confirm this. The ternary complexes with dipeptides (e.g. Gly-Ala, Gly-Ser, Gly-Met, Gly-Asp, Gly-Asn, Gly-His, Ser-Met, Asp-Phe, His-Gly) also favour the terminal amine as the axial donor with the proximate amide group binding to generate a five-ring chelate. Evidence for chelation through side-chain functionality was found only in the case of N-terminal Asp. The chiral environment about the ytterbium ion upon amino acid binding has also been probed using near-IR circular dichroism spectroscopy.
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|Publisher Web site:||http://dx.doi.org/10.1039/b311791j|
|Record Created:||15 May 2007|
|Last Modified:||08 Apr 2009 16:31|
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