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Interaction of metal ions and amino acids - Possible mechanisms for the adsorption of amino acids on homoionic smectite claysA semiempirical molecular orbital method is used to characterize the binding of amino acids to hexahydrated Cu(2+) and Ni(2+), a process presumed to occur when they are adsorbed in the interlamellar space of homoionic smectite clays. Five alpha-amino acids, beta-alanine, and gamma-aminobutyric acid were used to investigate the metal ion and amino acid specificity in binding. It was assumed that the alpha, beta, and gamma-amino acids would bind as bidentate anionic ligands, forming either 1:1 or 1:2 six-coordinated five, six, and seven-membered-ring chelate complexes, respectively. Energies of complex formation, optimized geometries, and electron and spin distribution were determined; and steric constraints of binding of the amino acids to the ion-exchanged cations in the interlamellar spacing of a clay were examined. Results indicate that hexahydrated Cu(2+) forms more stable complexes than hexahydrated Ni(2+) with all the amino acids studied. However, among these amino acids, complex formation does not favor the adsorption of the biological subset. Calculated energetics of complex formation and steric constraints are shown to predict that 1:1 rather than 1:2 metal-amino acid complexes are generally favored in the clay.
Document ID
19830048338
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Gupta, A.
(NASA Ames Research Center Moffett Field, CA, United States)
Loew, G. H.
(NASA Ames Research Center Moffett Field, CA, United States)
Lawless, J.
(NASA Ames Research Center Extraterrestrial Research Div., Moffett Field; Molecular Research Institute, Palo Alto, CA, United States)
Date Acquired
August 11, 2013
Publication Date
January 1, 1983
Publication Information
Publication: Inorganic Chemistry
Volume: 22
Issue: 1 19
ISSN: 0020-1669
Subject Category
Inorganic And Physical Chemistry
Accession Number
83A29556
Funding Number(s)
CONTRACT_GRANT: NCC2-96
Distribution Limits
Public
Copyright
Other

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