Metal Ion Complexes Containing Dipeptides, Tripeptides, and Biologically Important Zwitterionic 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 glycylglycine, glycylhistidine, glycylglycylglycine, glycylhistidylglycine, and Al(III), Ga(III), In(III), and Tl(I) with the biologically important secondary ligands bicine [N,N-bis(2hydroxyethyl)glycine], tricine [N,N,N-tris(hydroxymethyl)methylglycine], PIPES [piperazine-1,4-bis(2-ethanesulfonic acid)], HEPES (N-[2-hydroxyethyl]piperazine-N-[2-ethanesulfonic acid]), and EPPS 4-(2-hydroxyethyl)piperazine 1-propanesulfonic acid in a 1:1:1 ratio. Ternary complexes of the type Al(III)-glycylglycine-guanosine, Al(III)-glycylglycine-guanosine 5′-monophosphate (GMP), Al(III)-glycylglycylglycine-guanosine, Al(III)glycylglycylglycine-GMP, Al(III)-glycylhistidine-guanosine, Al(III)-glycylhistidine-GMP, Al(III)-glycylhistidylglycine-guanosine, Al(III)-glycylhistidylglycine-GMP in a 1:1:1 ratio have been investigated. The experimental conditions were selected such that self-association of the nucleotide and their complexes was negligibly small; that is, the monomeric normal and protonated complexes were studied. The formation of various mixed ligand complexes was inferred from the potentiometric titration curves. Initial estimates of the formation constants of the resulting species and the protonation constants of the different peptides and zwitterionic buffers used have been refined with the SUPERQUAD computer program. Confirmation of the formation of ternary complexes of the type M-P-Z in solution has been carried out using differential pulse polarography, square wave voltammetry, cyclic voltammetry, and UV spectroscopic measurements.

Spectroscopic, radiochemical, and theoretical studies of the Ga3+‐N‐2‐hydroxyethyl piperazine‐N′‐2‐ethanesulfonic acid (HEPES buffer) system: evidence for the formation of Ga3+‐ HEPES complexes in 68 Ga labeling reactions

“…We conclude that HEPES buffer used in the 68/67 Ga radiolabeling process is an undeniable, but weakly competitive chelator of Ga 3+ that interferes with the radiolabeling process. Our findings are in accordance with potentiometric studies, which proposed formation of a very weak 1:1 complex in solution (28). The formed complex was identified as a [ 68 Ga]Ga(HEPES) species via chromatographic comparison with the nonradioactive analog.…”

“…are 2 Â 10 8 and 81 for n = 3 and 4, respectively. The first of these values is probably too high, while the second is probably too low, although the latter is in agreement within one order of magnitude with the experimental reported value of logK = 1.99 AE 0.01 (28). For the zwitterionic species [GaHL(OH)(H 2 O) 3 ] 2+ , the value 2 Â 10 20 is obtained.…”

“…An early report explicitly mentions that no significant interactions between Ga 3+ and HEPES were found in aqueous solution using 71 Ga and 1 H NMR . However, a recent potentiometric study of the complexation of Ga 3+ with dipeptides and tripeptides in the presence of biologically relevant zwitterionic buffers reports a formation constant for a 1:1 Ga 3+ –HEPES species of log K 1 = 1.99 ± 0.01 mol dm −3 at 25 °C in the presence of 0.01 mm dm −3 KNO 3 .…”

Comparison of different phosphorus-containing ligands complexing 68Ga for PET-imaging of bone metabolism

“…HPLC analysis showed similar results compared to TLC. Beside this, a 68 Ga-intermediate is formed in the HEPES reaction buffer alone and the very weak Ga-HEPES complex itself [23] appears at 3.5 min retention time.…”

Fluorescence and Electrochemical Recognition of Nucleosides and DNA by A Novel Luminescent Bioprobe Eu(lll) -TNB

“…Herein, the aim of the present study is to examine the interaction of Eu(III) with TNB and nucleosides adenosine, guanosine, cytidine, inosine and with DNA. The present study can be considered as a continuation for the author work in the field of analytical applications of lanthanide complexes [41][42][43][44][45][46][47][48][49][50].…”