Header

UZH-Logo

Maintenance Infos

Stabilities and structures of metal ion complexes of adenosine 5‘-o-thiomonophosphate (AMPS2-) in comparison with those of its parent nucleotide (AMP2-) in aqueous solution


Sigel, Roland K O; Song, Bin; Sigel, Helmut (1997). Stabilities and structures of metal ion complexes of adenosine 5‘-o-thiomonophosphate (AMPS2-) in comparison with those of its parent nucleotide (AMP2-) in aqueous solution. Journal of the American Chemical Society, 119(4):744-755.

Abstract

The stability constants of the 1:1 complexes formed between Mg2+, Ca2+, Ba2+, Mn2+, Co2+, Ni2+, Zn2+, or Cd2+ and AMPS2-, i.e., of the M(AMPS) complexes, were determined by potentiometric pH titrations (25 °C; I = 0.1 M, NaNO3). For the Mn2+/AMPS, Co2+/AMPS, Ni2+/AMPS, and Cd2+/AMPS systems also the protonated species M(H;AMPS)+ were quantified, and for the Zn2+/AMPS system, the stability of the hydroxo species Zn(AMPS)(OH)-, which results from the Zn2+−thio coordination, could be determined. On the basis of previously established log versus p straight-line plots (R-MP2- = simple monophosphate ester ligands without further coordinating groups; Sigel, H.; et al. Helv. Chim. Acta 1992, 75, 2634), it is concluded that the alkaline earth ions in the M(AMPS) complexes are coordinated to the thiophosphate group with the same intensity as to a normal phosphate group. For the M(AMPS) complexes of Mn2+, Co2+, Ni2+, Zn2+, and Cd2+, it is shown by comparison with the corresponding M(AMP) complexes and by employing the mentioned straight-line plots that the stability increase is larger than may be expected due to macrochelate formation, which means that the metal ions also bind to the sulfur atom of the thiophosphate group. The stability increases amount for Mn(AMPS), Zn(AMPS), and Cd(AMPS) to about 0.2, 0.7, and 2.4 log units, respectively, and the estimated approximate percentages of the sulfur-coordinated species are about 30, 80, and 100%, respectively. Furthermore, comparisons between these stability increases and the solubility products for the corresponding metal ion sulfides, MIIS, as well as with the stability increases due to the M2+−thioether interaction observed for the complexes of tetrahydrothiophene-2-carboxylate, which also result in straight-line plots, further support the conclusions about metal ion−sulfur binding in the mentioned M(AMPS) complexes. The indicated correlations allow also an estimate for the extent of the M2+−sulfur interaction in Pb(AMPS) and Cu(AMPS). The various isomers of the M(H;AMPS)+ species are analyzed in a microconstant scheme, and estimations about their formation degrees are presented; for example, for the Cd2+ system, (H·AMPS·Cd)+ is the dominating isomer, which has the proton at N1 and Cd2+ at the thiophosphate group. It is evident that for metal ions like (Mn2+), Zn2+, or Cd2+ the metal ion binding properties of the parent compound AMP2- and its thio analogue AMPS2- differ considerably, and therefore, great care should be exercised in enzymatic studies where AMPS2- is employed as a probe for AMP2- in the presence of metal ions. Regarding studies of ribozymes, it is of interest that plots are presented (pseudo-first-order rate constants versus complex stabilities) which suggest that on top of a sulfur−metal ion interaction during the transition state of the rate-determining step of the hydrolytic cleavage of an oligonucleotide containing a bridged internucleotide 5‘-phosphorothioate RNA linkage also an oxygen−metal ion interaction occurs and that the two effects are “additive”.

Abstract

The stability constants of the 1:1 complexes formed between Mg2+, Ca2+, Ba2+, Mn2+, Co2+, Ni2+, Zn2+, or Cd2+ and AMPS2-, i.e., of the M(AMPS) complexes, were determined by potentiometric pH titrations (25 °C; I = 0.1 M, NaNO3). For the Mn2+/AMPS, Co2+/AMPS, Ni2+/AMPS, and Cd2+/AMPS systems also the protonated species M(H;AMPS)+ were quantified, and for the Zn2+/AMPS system, the stability of the hydroxo species Zn(AMPS)(OH)-, which results from the Zn2+−thio coordination, could be determined. On the basis of previously established log versus p straight-line plots (R-MP2- = simple monophosphate ester ligands without further coordinating groups; Sigel, H.; et al. Helv. Chim. Acta 1992, 75, 2634), it is concluded that the alkaline earth ions in the M(AMPS) complexes are coordinated to the thiophosphate group with the same intensity as to a normal phosphate group. For the M(AMPS) complexes of Mn2+, Co2+, Ni2+, Zn2+, and Cd2+, it is shown by comparison with the corresponding M(AMP) complexes and by employing the mentioned straight-line plots that the stability increase is larger than may be expected due to macrochelate formation, which means that the metal ions also bind to the sulfur atom of the thiophosphate group. The stability increases amount for Mn(AMPS), Zn(AMPS), and Cd(AMPS) to about 0.2, 0.7, and 2.4 log units, respectively, and the estimated approximate percentages of the sulfur-coordinated species are about 30, 80, and 100%, respectively. Furthermore, comparisons between these stability increases and the solubility products for the corresponding metal ion sulfides, MIIS, as well as with the stability increases due to the M2+−thioether interaction observed for the complexes of tetrahydrothiophene-2-carboxylate, which also result in straight-line plots, further support the conclusions about metal ion−sulfur binding in the mentioned M(AMPS) complexes. The indicated correlations allow also an estimate for the extent of the M2+−sulfur interaction in Pb(AMPS) and Cu(AMPS). The various isomers of the M(H;AMPS)+ species are analyzed in a microconstant scheme, and estimations about their formation degrees are presented; for example, for the Cd2+ system, (H·AMPS·Cd)+ is the dominating isomer, which has the proton at N1 and Cd2+ at the thiophosphate group. It is evident that for metal ions like (Mn2+), Zn2+, or Cd2+ the metal ion binding properties of the parent compound AMP2- and its thio analogue AMPS2- differ considerably, and therefore, great care should be exercised in enzymatic studies where AMPS2- is employed as a probe for AMP2- in the presence of metal ions. Regarding studies of ribozymes, it is of interest that plots are presented (pseudo-first-order rate constants versus complex stabilities) which suggest that on top of a sulfur−metal ion interaction during the transition state of the rate-determining step of the hydrolytic cleavage of an oligonucleotide containing a bridged internucleotide 5‘-phosphorothioate RNA linkage also an oxygen−metal ion interaction occurs and that the two effects are “additive”.

Statistics

Citations

121 citations in Web of Science®
114 citations in Scopus®
Google Scholar™

Altmetrics

Downloads

0 downloads since deposited on 24 Oct 2016
0 downloads since 12 months

Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Language:English
Date:1997
Deposited On:24 Oct 2016 14:53
Last Modified:18 May 2017 08:26
Publisher:American Chemical Society
ISSN:0002-7863
Publisher DOI:https://doi.org/10.1021/ja962970l

Download

Preview Icon on Download
Content: Published Version
Filetype: PDF - Registered users only
Size: 398kB
View at publisher

Article Networks

TrendTerms

TrendTerms displays relevant terms of the abstract of this publication and related documents on a map. The terms and their relations were extracted from ZORA using word statistics. Their timelines are taken from ZORA as well. The bubble size of a term is proportional to the number of documents where the term occurs. Red, orange, yellow and green colors are used for terms that occur in the current document; red indicates high interlinkedness of a term with other terms, orange, yellow and green decreasing interlinkedness. Blue is used for terms that have a relation with the terms in this document, but occur in other documents.
You can navigate and zoom the map. Mouse-hovering a term displays its timeline, clicking it yields the associated documents.

Author Collaborations