Header

UZH-Logo

Maintenance Infos

Acid-Base Properties of Adenosine 5′-O-Thiomonophosphate in Aqueous Solution


Song, Bin; Sigel, Roland K O; Sigel, Helmut (1997). Acid-Base Properties of Adenosine 5′-O-Thiomonophosphate in Aqueous Solution. Chemistry - A European Journal, 3(1):29-33.

Abstract

The acidity constants of H2-(AMPS)± were determined by potentiometric pH titrations in aqueous solution at 25°C and I=0.1M (NaNO3). Titrations with a combined single-junction glass electrode were hampered in the presence of AMPS by a “poisoning” effect; the problem could be avoided by use of two separated electrodes. The values of the acidity constants PKHH2(AMPS) = 3.72 ± 0.03 and pKHH2(AMPS) = 4.83 ± 0.02 are relatively close to each other; the buffer regions of the two equilibria overlap, and therefore a micro acidity constant scheme was developed and the constants for the various sites calculated. It is concluded that the thiophosphateprotonated species (AMPS⋅H)− dominates at about 75% occurrence, while the form (H⋅AMPS)−, with the proton at the N1 site of the adenine residue, occurs at about 25%. Semiempirical AM1 and PM3 calculations including water as a solvent locate the proton in (AMPS⋅H)− mainly on the terminal oxygen atoms rather than the sulfur. The acid-base properties of H2(AMPS)± are considerably more complicated than those of the parent nucleotide, H2(AMP)±; for the latter the two (intrinsic) acidity constants are well separated and consequently practically all protons have left the N1 site before deprotonation at the monoprotonated phosphate group occurs. Finally, an estimate for the acidity constants of H2(ATPγS)2- is given.

Abstract

The acidity constants of H2-(AMPS)± were determined by potentiometric pH titrations in aqueous solution at 25°C and I=0.1M (NaNO3). Titrations with a combined single-junction glass electrode were hampered in the presence of AMPS by a “poisoning” effect; the problem could be avoided by use of two separated electrodes. The values of the acidity constants PKHH2(AMPS) = 3.72 ± 0.03 and pKHH2(AMPS) = 4.83 ± 0.02 are relatively close to each other; the buffer regions of the two equilibria overlap, and therefore a micro acidity constant scheme was developed and the constants for the various sites calculated. It is concluded that the thiophosphateprotonated species (AMPS⋅H)− dominates at about 75% occurrence, while the form (H⋅AMPS)−, with the proton at the N1 site of the adenine residue, occurs at about 25%. Semiempirical AM1 and PM3 calculations including water as a solvent locate the proton in (AMPS⋅H)− mainly on the terminal oxygen atoms rather than the sulfur. The acid-base properties of H2(AMPS)± are considerably more complicated than those of the parent nucleotide, H2(AMP)±; for the latter the two (intrinsic) acidity constants are well separated and consequently practically all protons have left the N1 site before deprotonation at the monoprotonated phosphate group occurs. Finally, an estimate for the acidity constants of H2(ATPγS)2- is given.

Statistics

Citations

46 citations in Web of Science®
42 citations in Scopus®
Google Scholar™

Altmetrics

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:25 Oct 2016 14:53
Last Modified:18 May 2017 08:26
Publisher:Wiley-VCH Verlag Berlin
ISSN:0947-6539
Publisher DOI:https://doi.org/10.1002/chem.19970030106

Download

Full text not available from this repository.
View at publisher

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