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Binding of Oxovanadium( IV ) to Dipeptides Containing Histidine and Cysteine Residues
Author(s) -
Garribba Eugenio,
LodygaChruscinska Elzbieta,
Micera Giovanni,
Panzanelli Angelo,
Sanna Daniele
Publication year - 2005
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200400576
Subject(s) - chemistry , deprotonation , amide , ligand (biochemistry) , histidine , coordination sphere , potentiometric titration , medicinal chemistry , electron paramagnetic resonance , stereochemistry , aqueous solution , cysteine , polymer chemistry , ion , amino acid , organic chemistry , biochemistry , physics , receptor , nuclear magnetic resonance , enzyme
The complexation of the oxovanadium( IV ) ion with five dipeptides containing L ‐histidine or L ‐cysteine (GlyHis, HisHis, HisGly, CysGly, GlyCys) was studied. L ‐histidinamide (HisNH 2 ) was assumed as a model system for dipeptides with L ‐histidine in the N‐terminal position. The study was performed in aqueous solution through the combined application of potentiometric and spectroscopic (electronic absorption and EPR) techniques. The results indicate that simple dipeptides lacking a strong anchoring group can form mono‐ and bischelated complexes with the V IV O ion if a suitable “donor” is present in the chain. The ligands behave like amino acids in the acidic and neutral pH range, inhibit the precipitation of hydroxides and suppress the formation of hydrolytic species if at least a fivefold molar excess of ligand is used. In alkaline media all the ligands, except CysGly, promote the deprotonation and N‐coordination of the amide group. CysGly forms a bischelated complex with a [2 (NH 2 , S – )] donor set. The contribution of the deprotonated amide group to the 51 V hyperfine coupling constant, A z , as a function of the total equatorial charge of oxovanadium( IV ) ion, is discussed. The results have general validity and are useful to predict the geometry and donor set of complexes involving the bonding of the V IV O ion to the deprotonated amide group. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)