Ternary Complexes Formed by Trivalent Lanthanide Ions, Nucleotides, and Biological Buffers

Abstract

Potentiometric equilibrium measurements have been performed at (25.0 ( 0.1) °C and ionic strength I ) 0.1 mol dm -3 KNO 3 for the interaction of adenosine 5′-monophosphate, guanosine 5′-monophosphate, cytidine 5′-monophosphate, and La(III), Ce(III), Pr(III), and Eu(III) with the biologically important secondary ligand zwitterionic buffers (3-[N-morpholinol])-2-hydroxypropanesulfonic acid, 2-(N-morpholino)ethanesulfonic acid, N-2-acetamido-2-aminoethanesulfonic acid, and N-2-hydroxyethylpiperazine-N-2ethanesulfonic acid. Measurements were made in a 1:1:1 ratio. Formation constants for the monohydroxy, dihydroxy, and dimeric ligand complexes for the binary systems Ln(III) + adenosine 5′-monophosphate, Ln(III) + guanosine 5′-monophosphate, Ln(III) + cytidine 5′-monophosphate, and Ln(III) + zwitterionic buffers have been evaluated. The formation of various 1:1:1 normal and protonated mixed ligand complex species was inferred from the potentiometric pH-titration curves. The experimental conditions were selected such that self-association of the nucleotides and their complexes due to stacking interaction was negligibly small; that is, the monomeric normal and protonated ternary complexes were studied.

A comparative study of the effect of desferrioxamine B, oxalic acid, and Na-alginate on the desorption of U(VI) from goethite at pH 6 and 25°C

“…Product ( Anwar and Azab (2001) Reactants and products are presented consistent with the convention encountered in PHREEQC of describing charges and exponents. Ox À2 and Dfob À3 stand for the deprotonated forms of oxalate and DFO-B, respectively.…”

Cu(II) complexation by “non-coordinating” N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid (HEPES buffer)☆

“…An electrochemical study demonstrated that HEPES forms detectable, though weak complexes with Pb(II), but not with Zn(II) or Cd(II) [5]. A direct potentiometric study provided the stability constants for ML type complexes of HEPES with several lanthanides [6]. An indirect evidence for at least transient Au(III) complexation to HEPES was provided by a very recent study of DNA damage in the presence these two agents, where HEPES acted as a reductant for Au(III) and provided stabilization for a radical species [7].…”

Analysis of guanosine-5′-monophosphate at nM level based on the co-luminescence effect of Tb–Gd–GMP system

“…Linear range (mol/l) Linear regression equation (mol/l) r a LOD b (mol/l ) GMP 3 Â 10 À8 -3 Â 10 À5 I f =7.79+1.2 Â 10 7 C 0.9987 3.9 Â 10 À9 Table 4 Recoveries of GMP from synthetic samples Sample GMP added ( Â 10 À6 mol/l) GMP found ( Â 10 À6 mol/l) Average ( Â 10 À6 mol/l) RSD (%) Recovery (%) satisfy the coordination number for Tb 3+ and Gd 3+ [16].…”