title: The adsorption and reaction of adenine nucleotides on montmorillonite.
abstract: The binding of AMP to Zn(2+)-montmorillonite was investigated in the presence of buffers and salts.  Good's buffers, piperazine-N,N'-bis(2-ethanesulfonate) [PIPES] and morpholine-N-2-ethanesulfonate [MES], perturbed the exchangeable cations to a lesser extent (only 9% of Zn2+ displaced by 0.2 M buffer) than was observed with imidazole and lutidine buffers or NaCl and KCl salts (up to 80% of Zn2+ displaced).  AMP adsorption isotherms measured in the presence of 0.2 M PIPES, MES, or Na2SO4 exhibited normal Langmuir-type behavior.  The adsorption coefficient, KL, is 3-fold greater in the presence of HEPES or PIPES than it is in the absence of buffers.  Basal spacings measured by X-ray diffraction for Zn(2+)-montmorillonite are 13 and 15 angstroms in the presence of PIPES, while a value of 12.8 angstroms was determined in the absence of PIPES.  These data are interpreted in a model in which the adsorption of AMP is mediated by a Zn2+ complex of PIPES in different orientations in the interlamellar region of the montmorillonite.  The type of exchangeable cation does not affect the ability of the lattice-bound Fe3+ in the montmorillonite to oxidize diaminomaleonitrile (DAMN).  Exchangeable Cu2+ oxidizes DAMN, but exchangeable Fe3+ is nearly ineffective as an oxidant.  The addition of DISN to 3'-AMP bound to Zn(2+)-montmorillonite in the presence of 0.2 M PIPES resulted in a higher yield of 2',3'-cAMP than is observed with a comparable concentration of Zn2+, a result which inplicates surface catalysis by the montmorillonite.
authors.affiliation: Department of Chemistry, Rensselaer Polytechnic Institute, Troy, NY 12180-3590, USA.
authors.forename: J P
authors.initials: JP
authors.lastname: Ferris
authors.forename: W J
authors.initials: WJ
authors.lastname: Hagan
mesh_terms: D000227:Adenine Nucleotides / Q000737:chemistry*; D000249:Adenosine Monophosphate / Q000737:chemistry*; D000327:Adsorption; D017738:Alkanesulfonic Acids / Q000737:chemistry; D001546:Bentonite / Q000737:chemistry*; D002021:Buffers; D002412:Cations; D000242:Cyclic AMP / Q000138:chemical synthesis*; D019143:Evolution, Molecular; D006531:HEPES / Q000737:chemistry; D009025:Morpholines / Q000737:chemistry; D009570:Nitriles / Q000737:chemistry; D010084:Oxidation-Reduction; D010879:Piperazines / Q000737:chemistry; D015032:Zinc / Q000737:chemistry*
chemical_list: D000227:Adenine Nucleotides; D017738:Alkanesulfonic Acids; D002021:Buffers; D002412:Cations; D009025:Morpholines; D009570:Nitriles; D010879:Piperazines; D001546:Bentonite; C022103:diaminomaleonitrile; C047926:diiminosuccinonitrile; C004550:2-(N-morpholino)ethanesulfonic acid; D000249:Adenosine Monophosphate; D000242:Cyclic AMP; C008916:piperazine-N,N'-bis(2-ethanesulfonic acid); D015032:Zinc; D006531:HEPES