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- Title
Computational evaluation of pK for oxygenated side chain containing amino acids interacting with Aluminum.
- Authors
Mujika, J.; Ugalde, J.; Lopez, X.
- Abstract
The acidity of oxygen containing amino acids (Asp, Tyr, Ser, Thr) and the chemically analogue S-containing Cys was investigated using quantum mechanical methods when these amino acids interact with Al(III). The pK values of these residues were determined calculating the free energy of a proton transfer reaction from the metal-bound amino acid to a reference molecule, a water molecule interacting with the cation. In addition, for comparison, since Al(III) can replace Mg(II) in certain proteins, the acidity of these O-containing amino acid was also computed when they interact with Mg(II). All calculations were carried out combining the B3LYP density function method with the polarizable continuum PCM model. Our results confirm that the second solvation sphere water molecules must explicitly be included for an accurate description of interaction between the solute and the solvent. The computed pK values show that the acidity of all amino acids is enhanced when they interact with both cations. However, the pK values are significantly lower with Al(III) than with Mg(II). This difference in the acidity may lead to drastic chemical changes in proteins where Al(III) substitutes Mg(II). The present work allows to quantify the acidity shift of the title amino acids due to the influence of Al(III) and provides a valuable information for a better understanding of its biological consequences.
- Subjects
AMINO acids; MOLECULE-molecule collisions; ALUMINUM; QUANTUM theory; PROTON transfer reactions; COMPARATIVE studies; SUBSTITUTION reactions; ACIDITY function
- Publication
Theoretical Chemistry Accounts: Theory, Computation, & Modeling, 2011, Vol 128, Issue 4-6, p477
- ISSN
1432-881X
- Publication type
Article
- DOI
10.1007/s00214-010-0807-6