Wydział Chemii

A. Odani

Henryk Kozłowski

Jolanta Świątek-Kozłowska

Justyna Brasuń

B. P. Operschall

Helmut Sigel

2007

Journal of Inorganic Biochemistry

101

727-735

10.1016/j.jinorgbio.2006.12.014

Naukowa

Angielski

Artykuł

Previously published stability constants of several metal ion (M²⁺) complexes formed with thiouridines and their 5′-monophosphates, together with recently obtained versus plots for M²⁺ complexes of uridinate derivatives (U⁻) allowed now a quantitative evaluation of the effect that the exchange of a (C)O by a (C)S group has on the stability of the corresponding complexes. For example, the stability of the Ni²⁺, Cu²⁺ and Cd²⁺ complexes of 2-thiouridinate is increased by about 1.6, 2.3, and 1.3 log units, respectively, by the indicated exchange of groups. Similar results were obtained for other thiouridinates, including 4-thiouridinate. The structure of these complexes and the types of chelates formed (involving (N3)⁻ and (C)S) are discussed. A recently advanced method for the quantification of the chelate effect allows now also an evaluation of several complexes of thiouridinate 5′-monophosphates. In most instances the thiouracilate coordination dominates the systems, allowing only the formation of small amounts of phosphate-bound isomers. Among the complexes studied only the one formed by Cu²⁺ with 2-thiouridinate 5′-monophosphate leads to significant amounts of the macrochelated isomer, which means that in this case Cu²⁺ is able to force the nucleotide from the anti to the syn conformation, allowing thus metal ion binding to both potential sites and this results in the formation of about 58% of the macrochelated isomer. The remaining 42% are species in which Cu²⁺ is overwhelmingly coordinated to the thiouracilate residue; Cu²⁺ binding to the phosphate group occurs in this case only in trace amounts.

Chelate formation, Isomeric equilibria, Metal ion–sulfur coordination, Thiouridine 5′-monophosphates, Thiouridines

https://doi.org/10.1016/j.jinorgbio.2006.12.014

http://www.elsevier.com