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Nickel(II), Copper(II) and Zinc(II) Complexes of 9-[2- (Phosphonomethoxy)ethyl]-8-azaadenine (9,8aPMEA), the 8-Aza Derivative of the Antiviral Nucleotide Analogue 9-[2-(Phosphonomethoxy)ethyl] adenine (PMEA). Quantification of Four Isomeric Species in Aqueous Solution
The acidity constants of the twofold protonated acyclic nucleotide analogue 9-[2-(phosphonomethoxy)- ethyl]-8-azaadenine, H(2)(9,8aPMEA)(±), as well as the stability constants of the M(H;9,8aPMEA)(+) and M(9,8aPMEA) complexes with the metal ions M(2+) =Ni(2+), Cu(2+) or Zn(2+), have been determined...
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Formato: | Texto |
Lenguaje: | English |
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Hindawi Publishing Corporation
2004
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Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2267076/ https://www.ncbi.nlm.nih.gov/pubmed/18365084 http://dx.doi.org/10.1155/S1565363304000202 |
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author | Gómez-Coca, Raquel B. Holý, Antonín Vilaplana, Rosario A. González-Vílchez, Francisco Sigel, Helmut |
author_facet | Gómez-Coca, Raquel B. Holý, Antonín Vilaplana, Rosario A. González-Vílchez, Francisco Sigel, Helmut |
author_sort | Gómez-Coca, Raquel B. |
collection | PubMed |
description | The acidity constants of the twofold protonated acyclic nucleotide analogue 9-[2-(phosphonomethoxy)- ethyl]-8-azaadenine, H(2)(9,8aPMEA)(±), as well as the stability constants of the M(H;9,8aPMEA)(+) and M(9,8aPMEA) complexes with the metal ions M(2+) =Ni(2+), Cu(2+) or Zn(2+), have been determined by potentiometric pH titrations in aqueous solution at I=0.1 M (NaNO(3)) and 25℃. The result for the release of the first proton from H(2)(9,8aPMEA)(+) (pK(a)= 2.73), which originates from the (N1)H(+) site, was confirmed by UV-spectrophotometric measurements. Application of previously determined straight-line plots of log KMM(R-PO(3)) versus PKH(3)(R-HPO(3))' for simple phosph(on)ate ligands, R- PO-, where R represents a residue without an affinity for metal ions, proves that the primary binding site of 9,8aPMEA(2-) is the phosphonate group for all three metal ions studied. By stability constant comparisons with related ligands it is shown, in agreement with conclusions reached earlier for the Cu(PMEA) system [PMEA(2-)=dianion of 9-[2- (phosphonomethoxy)ethyl]adenine], that in total four different isomers are in equilibrium with each other, i.e. (i) an open isomer with a sole phosphonate coordination, M(PA)(op), where PA(2-)=PMEA(2-)or 9,8aPMEA(2-), (ii) an isomer with a 5-membered chelate involving the ether oxygen, M(PA)cl/o, (iii) an isomer which contains 5- and 7-membered chelates formed by coordination of the phosphonate group, the ether oxygen and the N3 site of the adenine residue, M(PA)(cl/O/N3), and finally (iv) a macrochelated isomer involving N7, M(PA)(cl/]N7). The Cu(2+) systems of PMEA(2-) and 9,8aPMEA(2-) behave quite alike; the formation degrees for Cu(PA)(op), CuM(PA)(cl/O), Cu(PA)(cl/O/N3) and Cu(PA)(cl/N3) are approximately 16, 32, 45 and 7%, respectively, which shows that Cu(PA)(cl/N7) is a minority species. In the Ni(2+) and Zn(2+) systems the open isomer is the dominating one followed by M(PA)(cl/O), but there are indications that the other two isomers also occur to some extent. |
format | Text |
id | pubmed-2267076 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2004 |
publisher | Hindawi Publishing Corporation |
record_format | MEDLINE/PubMed |
spelling | pubmed-22670762008-03-24 Nickel(II), Copper(II) and Zinc(II) Complexes of 9-[2- (Phosphonomethoxy)ethyl]-8-azaadenine (9,8aPMEA), the 8-Aza Derivative of the Antiviral Nucleotide Analogue 9-[2-(Phosphonomethoxy)ethyl] adenine (PMEA). Quantification of Four Isomeric Species in Aqueous Solution Gómez-Coca, Raquel B. Holý, Antonín Vilaplana, Rosario A. González-Vílchez, Francisco Sigel, Helmut Bioinorg Chem Appl Research Article The acidity constants of the twofold protonated acyclic nucleotide analogue 9-[2-(phosphonomethoxy)- ethyl]-8-azaadenine, H(2)(9,8aPMEA)(±), as well as the stability constants of the M(H;9,8aPMEA)(+) and M(9,8aPMEA) complexes with the metal ions M(2+) =Ni(2+), Cu(2+) or Zn(2+), have been determined by potentiometric pH titrations in aqueous solution at I=0.1 M (NaNO(3)) and 25℃. The result for the release of the first proton from H(2)(9,8aPMEA)(+) (pK(a)= 2.73), which originates from the (N1)H(+) site, was confirmed by UV-spectrophotometric measurements. Application of previously determined straight-line plots of log KMM(R-PO(3)) versus PKH(3)(R-HPO(3))' for simple phosph(on)ate ligands, R- PO-, where R represents a residue without an affinity for metal ions, proves that the primary binding site of 9,8aPMEA(2-) is the phosphonate group for all three metal ions studied. By stability constant comparisons with related ligands it is shown, in agreement with conclusions reached earlier for the Cu(PMEA) system [PMEA(2-)=dianion of 9-[2- (phosphonomethoxy)ethyl]adenine], that in total four different isomers are in equilibrium with each other, i.e. (i) an open isomer with a sole phosphonate coordination, M(PA)(op), where PA(2-)=PMEA(2-)or 9,8aPMEA(2-), (ii) an isomer with a 5-membered chelate involving the ether oxygen, M(PA)cl/o, (iii) an isomer which contains 5- and 7-membered chelates formed by coordination of the phosphonate group, the ether oxygen and the N3 site of the adenine residue, M(PA)(cl/O/N3), and finally (iv) a macrochelated isomer involving N7, M(PA)(cl/]N7). The Cu(2+) systems of PMEA(2-) and 9,8aPMEA(2-) behave quite alike; the formation degrees for Cu(PA)(op), CuM(PA)(cl/O), Cu(PA)(cl/O/N3) and Cu(PA)(cl/N3) are approximately 16, 32, 45 and 7%, respectively, which shows that Cu(PA)(cl/N7) is a minority species. In the Ni(2+) and Zn(2+) systems the open isomer is the dominating one followed by M(PA)(cl/O), but there are indications that the other two isomers also occur to some extent. Hindawi Publishing Corporation 2004 /pmc/articles/PMC2267076/ /pubmed/18365084 http://dx.doi.org/10.1155/S1565363304000202 Text en Copyright © 2004 Raquel B. Gómez-Coca et al. http://creativecommons.org/licenses/by/2.0 This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. |
spellingShingle | Research Article Gómez-Coca, Raquel B. Holý, Antonín Vilaplana, Rosario A. González-Vílchez, Francisco Sigel, Helmut Nickel(II), Copper(II) and Zinc(II) Complexes of 9-[2- (Phosphonomethoxy)ethyl]-8-azaadenine (9,8aPMEA), the 8-Aza Derivative of the Antiviral Nucleotide Analogue 9-[2-(Phosphonomethoxy)ethyl] adenine (PMEA). Quantification of Four Isomeric Species in Aqueous Solution |
title | Nickel(II), Copper(II) and Zinc(II) Complexes of 9-[2- (Phosphonomethoxy)ethyl]-8-azaadenine (9,8aPMEA),
the 8-Aza Derivative of the Antiviral Nucleotide Analogue 9-[2-(Phosphonomethoxy)ethyl] adenine (PMEA). Quantification of Four Isomeric Species in Aqueous Solution |
title_full | Nickel(II), Copper(II) and Zinc(II) Complexes of 9-[2- (Phosphonomethoxy)ethyl]-8-azaadenine (9,8aPMEA),
the 8-Aza Derivative of the Antiviral Nucleotide Analogue 9-[2-(Phosphonomethoxy)ethyl] adenine (PMEA). Quantification of Four Isomeric Species in Aqueous Solution |
title_fullStr | Nickel(II), Copper(II) and Zinc(II) Complexes of 9-[2- (Phosphonomethoxy)ethyl]-8-azaadenine (9,8aPMEA),
the 8-Aza Derivative of the Antiviral Nucleotide Analogue 9-[2-(Phosphonomethoxy)ethyl] adenine (PMEA). Quantification of Four Isomeric Species in Aqueous Solution |
title_full_unstemmed | Nickel(II), Copper(II) and Zinc(II) Complexes of 9-[2- (Phosphonomethoxy)ethyl]-8-azaadenine (9,8aPMEA),
the 8-Aza Derivative of the Antiviral Nucleotide Analogue 9-[2-(Phosphonomethoxy)ethyl] adenine (PMEA). Quantification of Four Isomeric Species in Aqueous Solution |
title_short | Nickel(II), Copper(II) and Zinc(II) Complexes of 9-[2- (Phosphonomethoxy)ethyl]-8-azaadenine (9,8aPMEA),
the 8-Aza Derivative of the Antiviral Nucleotide Analogue 9-[2-(Phosphonomethoxy)ethyl] adenine (PMEA). Quantification of Four Isomeric Species in Aqueous Solution |
title_sort | nickel(ii), copper(ii) and zinc(ii) complexes of 9-[2- (phosphonomethoxy)ethyl]-8-azaadenine (9,8apmea),
the 8-aza derivative of the antiviral nucleotide analogue 9-[2-(phosphonomethoxy)ethyl] adenine (pmea). quantification of four isomeric species in aqueous solution |
topic | Research Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2267076/ https://www.ncbi.nlm.nih.gov/pubmed/18365084 http://dx.doi.org/10.1155/S1565363304000202 |
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