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| Content Provider | Springer Nature Link |
|---|---|
| Author | Da Costa, Carla P. Sigel, H. |
| Copyright Year | 1999 |
| Abstract | The stability constants of the 1 : 1 complexes formed between Pb2+ and several simple phosphate monoesters (4-nitrophenyl phosphate, phenyl phosphate, d-ribose 5-monophosphate, n-butyl phosphate) or phosphonate ligands (methylphosphonate, ethylphosphonate) (R-PO2– 3) were determined by potentiometric pH titrations in aqueous solution (25 °C;I=0.1 M, NaNO3). The construction of a log K P P b b(R-PO3) versus pK H H(R-PO3) plot for the mentioned ligand systems results in a straight line on which the data pairs (the corresponding equilibrium constants were also measured) for uridine 5′-monophosphate (UMP2–) and thymidine 5′-monophosphate (dTMP2–) also fall; this result shows that in the Pb2+ complexes of UMP2– and dTMP2– the nucleobase residues do not interfere, in neither a positive nor a negative way, with the binding of Pb2+ and that the stability of all these complexes is determined by the basicity of the phosph(on)ate group. The mentioned straight-line correlation (as defined by the least-squares procedure) allowed us to demonstrate (via constants determined now) that the stability of the Pb2+ complex of cytidine 5′-monophosphate (CMP2–) is also solely determined by the basicity of its phosphate group. A similar evaluation, based on literature data, for the Pb(HPO4) complex reveals that its stability corresponds closely to the expectations based on the Pb(R-PO3) data, though there is a slight hint that Pb(HPO4) may be somewhat more stable [which would be in agreement with previous observations of other M(HPO4) complexes]; clearly, more such comparisons are possible with the reference line given now. Based on the stability constants of the monoprotonated Pb(H;CMP)+ complex and the Pb(cytidine)2+ species (which was also measured now), it is concluded that in Pb(H;CMP)+ the proton is located at the phosphate group and Pb2+ mainly at the N3/(C2)O site of the cytosine residue. Regarding nucleic acids in solution, it is further concluded that the affinity of Pb2+ towards the negatively mono-charged phosphate unit, —O—P(O)2 –—O—, of a nucleic acid backbone is comparable to that of the cytosine moiety, the affinity towards other nucleobase residues being smaller. This information may prove helpful regarding the properties of lead ribozymes. |
| Starting Page | 508 |
| Ending Page | 514 |
| Page Count | 7 |
| File Format | |
| ISSN | 09498257 |
| Journal | JBIC Journal of Biological Inorganic Chemistry |
| Volume Number | 4 |
| Issue Number | 4 |
| e-ISSN | 14321327 |
| Language | English |
| Publisher | Springer-Verlag |
| Publisher Date | 1999-08-23 |
| Publisher Place | Berlin, Heidelberg |
| Access Restriction | One Nation One Subscription (ONOS) |
| Content Type | Text |
| Resource Type | Article |
| Subject | Biochemistry Inorganic Chemistry |
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