Xanthosine 5′-monophosphate (XMP). Acid–base and metal ion-binding properties of a chameleon-like nucleotide

Sigel, Helmut and Operschall, Bert P. and Griesser, Rolf. (2009) Xanthosine 5′-monophosphate (XMP). Acid–base and metal ion-binding properties of a chameleon-like nucleotide. Chemical Society Reviews, 38 (8). pp. 2465-2494.

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The four acidity constants of threefold protonated xanthosine 5`-monophosphate, H-3(XMP)(+), reveal that in the physiological pH range around 7.5 (X - H.MP)(3-) strongly dominates and not XMP2- as commonly given in textbooks and often applied in research papers. Therefore, this nucleotide, which participates in many metabolic processes, should be addressed as xanthosinate 5`-monophosphate as is stated in this critical review. Micro acidity constant schemes allow quantification of intrinsic site basicities. In 9-methylxanthine nucleobase deprotonation occurs to more than 99% at (N3) H, whereas for xanthosine it is estimated that about 30% are (N1) H deprotonated and for (X - H.MP)(3-) it is suggested that (N1)H deprotonation is further favored, especially in macrochelates where the phosphate-coordinated M2+ interacts with N7. The formation degree of these macrochelates in the (X - H.MP.M)(-) species of Co2+, Ni2+, Cu2+, Zn2+ or Cd2+ amounts to 90% or more. In the monoprotonated (M.X - H.MP.H)(+/-) complexes, M2+ is located at the N7/[(C6)O] unit as the primary binding site and it forms macrochelates with the P(O)(2)(OH)(-) group to about 65% for nearly all metal ions considered (i. e., including Ba2+, Sr2+, Ca2+, Mg2+); this indicates outer-sphere binding to P(O)(2)(OH). Finally, a new method quantifying the chelate effect is applied to the M(X - H.MP)(-) species, stabilities and structures of mixed-ligand complexes are considered, and the stability constants for several M(X - H.DP)(2-) and M(X - H.TP)(3-) complexes are estimated (112 references).
Faculties and Departments:05 Faculty of Science > Departement Chemie > Chemie
UniBasel Contributors:Operschall, Bert P. and Griesser, Rolf and Sigel, Helmut
Item Type:Article, refereed
Article Subtype:Book Review
Publisher:Royal Society of Chemistry
Note:Publication type according to Uni Basel Research Database: Journal item
Identification Number:
Last Modified:12 Dec 2016 11:36
Deposited On:12 Dec 2016 11:36

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