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The formation of binary and ternary complexes of Cu(II), Ni(II), Co(II), Mn(II), Zn(II), Ca(II), Mg(II), and Pd(II) with 4-morpholinoethane sulfonic acid (MES), 2-(cyclohexylamino)ethane sulfonic a...

The solid complex Tb(III)-bathophenanthroline (Bphen) was synthesized and characterized by elemental analysis, IR spectra, and thermalanalysis. The formation of binary and ternary complexes of Tb(III) with N-acetylamino acids (N-acetylaspartic acid, N-acetylhistidine, and N-acetylhistamine), and Bphen or anthracene-9-carboxylic acid (9-ANCA) has been studied potentiometrically at (25.0 ± 0.1) °C and an ionic strength of I = 0.1 mol·dm–3. The results obtained confirmed the recognition of the investigated N-acetylamino acids by the luminescent probes used at the molecular level. The formation of binary and ternary complexes of Tb(III) with nucleotides guanosine 5′-monophosphate (5′-GMP), adenosine 5′-monophosphate (5′-AMP), cytidine 5′-monophosphate (5′-CMP), or N-acetylamino acids (N-acetylaspartic acid, N-acetylhistidine, and N-acetylhistamine) has been studied potentiometrically. Confirmation of the formation of the ternary systems of the type Tb(III)-Bphen-N-acetylamino acids or Tb(III)-9-ANCA-N-acetyla...

The formation of binary and ternary model complexes of Eu(III) with the nucleobases 5-aminouracil (5-amino 2,4-dioxy pyrimidine), dihydrouracil (5,6-dihydro-2,4-dioxy pyrimidine), thymine (2,4-dihydroxy 5-methyl pyrimidine), adenine (6-aminopurine), uracil (2,4-dioxy pyrimidine), and PIPES (piperazine 1,4-bis(2-ethane sulfonic acid) dissodium salt) has been studied potentiometrically at (25.0 ± 0.1) °C and at an ionic strength of I = 0.1 mol·dm−3 (KNO3). The formation of the 1:1, 2:1 binary, and 1:1:1 and 2:1:1 ternary complexes is inferred from the corresponding titration curves. Initial estimates of the formation constants of the resulting species and the protonation constants of the different ligands used have been refined with the SUPERQUAD computer program. The experimental conditions were selected such that self-association of the nucleobases and their complexes was negligibly small; that is, the monomeric and protonated complexes were studied. Recognition of nucleobases and CT-DNA by the luminescen...

The solid complex Eu(III)−bathophenanthroline was synthesized and characterized by elemental analysis, IR spectra, and thermal analysis. The interaction of the Eu(III)−bathophenanthroline solid complex with calf-thymus DNA has been investigated by fluorescence and electrochemical methods including cyclic voltammetery and differential pulse polarography on a glassy carbon electrode. The formation of binary and ternary complexes of Eu(III) with nucleotides guanosine 5′- monophosphate (5′-GMP), adenosine 5′-monophosphate (5′-AMP), inosine 5′-monophosphate (5′-IMP), cytidine 5′-monophosphate (5′-CMP), or N-acetylamino acids (N-acetylaspartic acid, N-acetylhistidine, and N-acetylhistamine), and bathophenanthroline (BPhen) has been studied potentiometrically at (25.0 ± 0.1) °C and an ionic strength of I = 0.1 mol·dm−3 (KNO3) in 1.8 % v/v ethanol−water mixture solvent. The formation of the normal and protonated binary and ternary complexes is inferred from the corresponding titration curves. The experimental con...

The interaction of Eu(9-ANCA)3 (9-ANCA = anthracene-9-carboxylic acid) with DNA has been investigated by a fluorescence method. Potentiometric equilibrium measurements have been performed at (25.0 ± 0.1) °C and ionic strength I = 0.1 mol·dm−3 KNO3 for the interaction of Eu(III) and 9-ANCA with adenosine 5′-diphosphate (ADP), adenosine 5′-triphosphate (ATP), N-acetyl glutamic acid (Nc-Glu), N-acetyl leucine (Nc-Leu), and N-acetyl lysine (Nc-Lys) in a 1:1:1 ratio. The formation of various mixed ligand complexes was inferred from the potentiometric titration curves. The formation constants of the binary and ternary complexes have been refined with the SUPERQUAD computer program. The interaction of Eu(III)-(9-ANCA) with Nc-Glu, Nc-Leu, and Nc-Lys has been investigated by electroanalytical methods including cyclic voltammetry (CV), differential pulse polarography (DPP), and square wave voltammetry (SWV) on a glassy carbon (GC) electrode.

Potentiometric equilibrium measurements have been performed at (25.0 ± 0.1) °C and ionic strength I = 0.1 mol·dm−3 KNO3 for the interaction of the biologically important ligands N-acetylhistidine, N-acetyl l-leucine, N-acetylglutamic acid, N-acetylhistamine, N-acetylaspartic acid, and La(III), Gd(III), Sm(III), Tb(III), Eu(III), and Dy(III) with the nucleotides guanosine 5′-monophosphate (5′-GMP), cytedine 5′-monophosphate (5′-CMP), inosine 5′-monophosphate (5′-IMP), adenosine 5′-monophosphate (5′-AMP), adenosine 5′-diphosphate (5′-ADP), adenosine 5′-triphosphate (5′-ATP), and cytedine 5′-triphosphate (5′-CTP) in 1:1:1 and 1:2:1 ratios. The formation constants of various mixed ligand complexes were inferred from the potentiometric titration curves. Initial estimates of the formation constants of the resulting species and the formation constants of the different N-acetyl amino acid (NAA) and nucleotide (NU) complexes in metal ligand ratios 1:1 and 2:1 have been refined with the SUPERQUAD computer program. ...

The formation of binary and ternary complexes of Eu(III) with nucleobases (NB), guanine (2-amino-6-oxypurine), thymine (2,4-dihydroxy 5-methyl pyrimidine), adenine (6-aminopurine), uracil (2,4-dioxypyrimidine), and anthracene-9-carboxylic acid (ANCA) has been studied potentiometrically at (25.0 ± 0.1) °C and ionic strength I = 0.1 mol·dm−3 (KNO3) in 10 % ethanol−water mixture solvent. The acid−base properties of the ligands were investigated and discussed. The formation of the 1:1, 2:1 binary, and 1:1:1 and 2:1:1 ternary complexes is inferred from the corresponding titration curves. The ternary complexes formed are monoprotonated complexes. The stability constants of the binary and ternary systems were evaluated. Initial estimates of the formation constants of the resulting species and the protonation constants of the different ligands used have been refined with the SUPERQUAD computer program. The experimental conditions were selected such that self-association of the nucleobase and their complexes was n...

Potentiometric equilibrium measurements have been performed at (25.0 ± 0.1) °C and ionic strength I = 0.1 mol·dm-3 KNO3 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(2-hydroxyethyl)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 se...

The apparent dissociation constants of the nucleobases guanine, thymine, uracil, hypoxanthine, and cytosine were determined at (25.0 ± 0.1) °C and I = 0.1 mol·dm-3 (KNO3) by potentiometric pH titration in pure water and different hydroorganic solvent media. The organic solvents used were methanol and ethanol as amphiprotic hydrogen bond acceptor−donor (HBA-D) solvents, N,N-dimethylformamide (DMF), dimethyl sulfoxide, acetone, and dioxane as hydrogen bond acceptor solvents. A computer program was used to refine the initial estimates of the apparent dissociation constants of the five purine and pyrimidine nucleobases. The results obtained are discussed in terms of average macroscopic properties of the mixed solvents. The effects of organic cosolvents on the acid dissociation equilibria have been interpreted using the solvatochromic quantitative values of Kamlet−Taft hydrogen bond acidity and basicity (α, β) and dipolarity polarizability π* of the solvent. The free energy of transfer of the protons from wate...

Potentiometric equilibrium measurements have been performed at (25.0 ± 0.1) °C and ionic strength I = 0.1 mol·dm-3 (KNO3) for the interaction of guanine (2-amino-6-oxypurine), thymine (2,4-dihydroxy-5-methylpyrimidine), adenine (6-aminopurine), uracil (2,4-dioxypyrimidine), hypoxanthine (6-oxypurine), and Cu(II), Ni(II), Co(II), Mn(II), Zn(II), Ca(II), and Mg(II) with the biologically important secondary ligands glycine (aminoethanoic acid), bicine [N,N-bis(2-hydroxyethyl)glycine], tricine [N,N,N-tris(hydroxymethyl)methylglycine], and ADA [N-(2-acetamido)-3-iminodiacetic acid] in a 1:1:1 ratio. The experimental conditions were selected such that self-association of the nucleobases and their complexes was negligibly small; that is, the monomeric normal and protonated complexes were studied. The formation of various 1:1:1 mixed ligand complexes was inferred from the potentiometric titration curves. Initial estimates of the formation constants of the resulting species and the acid dissociation constants of g...

Potentiometric equilibrium measurements have been performed at (25.0 ± 0.1) °C and ionic strength I = 0.1 mol dm-3 KNO3 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-2-ethanesulfonic 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...

Potentiometric equilibrium measurements have been performed at (25.0 ± 0.1) °C and ionic strength I = 0.1 mol dm-3 KNO3 for the interaction of the purine nucleotides adenosine 5‘-mono, 5‘-di, and 5‘-triphosphate and Cu(II), Co(II), Ni(II), Mn(II), Zn(II), Ca(II), and Mg(II) with the biologically important secondary ligand zwitterionic buffers 3-(N-morpholino)propanesulfonic acid, 3-[(1,1-dimethyl-2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid, N-(2-hydroxyethyl)piperazine-N‘-2-hydroxypropanesulfonic acid, piperazine-N,N‘-bis(2-ethanesulfonic acid), and piperazine-N,N‘-bis(2-hydroxypropanesulfonic acid) in a 1:1:1 ratio and 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 purine nucleotides and their complexes was negligibly small; i.e., the monomeric normal and protonated ternary complexes were studied. Initial estimates of the formatio...

Potentiometric equilibrium measurements have been performed at (25.0 ± 0.1) °C and ionic strength I = 0.1 mol dm-3 (KNO3) for the interaction of guanosine 5‘-monophosphate, inosine 5‘-monophosphate...

Potentiometric equilibrium measurements have been performed at (25.0 ± 0.1) °C and ionic strength I = 0.1 mol dm-3 KNO3 for the interaction of adenosine 5‘-mono-, 5‘-di-, and 5‘-triphosphate and Cu(II), Co(II), Ni(II), Mn(II), Zn(II), Ca(II), and Mg(II) with the biologically important secondary ligand zwitterionic buffers 3-[N-bis(hydroxyethyl)amino]-2-hydroxypropanesulfonic acid, 3-[N-tris(hydroxymethyl)methylamino]-2-hydroxypropanesulfonic acid, (3-[N-morpholinol)-2-hydroxy propanesulfonic acid, N-(2-acetamido)-2-aminoethanesulfonic acid, and 2-(cyclohexylamino)ethanesulfonic acid in a 1:1:1 ratio, and 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 was negligibly small; i.e., the monomeric normal and protonated ternary complexes were studied. Initial estimates of the formation constants of the resulting sp...

Potentiometric equilibrium measurements have been performed at (25.0 ± 0.1) °C and ionic strength I = 0.1 mol dm-3 (KNO3) for the interaction of glycine (aminoethanoic acid), serine (2-amino-3-hydroxypropanoic acid), methionine (2-amino-4-(methylthio)butanoic acid), aspartic acid (aminobutanedioic acid), glutamic acid (2-aminopropanedioic acid), and histidine (α-amino-1H-imidazole-4-propanoic acid) and Cu(II), Co(II), Ni(II), Mn(II), and Zn(II) with the biologically important secondary ligand zwitterionic buffers β-hydroxy-4-morpholinepropanesulfonic acid (MOPSO), 4-morpholinepropanesulfonic acid (MOPS), 3-[bis(2-hydroxyethyl)amino]-2-hydroxy-1-propanesulfonic acid (DIPSO), and 3-[N-tris(hydroxymethyl)methyl)amino]-2-hydroxypropanesulfonic acid (TAPSO) in 1:1:1 and 1:1:2 ratios, and the formation of various 1:1:1 ternary complexes and 1:1:2 quaternary complex species was inferred from the potentiometric pH titration curves. Initial estimates of the formation constants of the resulting species and the acid...

The apparent second stage dissociation constants of piperazine-N,N-bis[2-hydroxypropanesulfonicacid] (POPSO), N-[2-hydroxyethy1]piperazine-N‘-3-propane sulfonic acid (HEPPS), 2-[N-cyclohexylamino]ethanesulfonic acid (CHES) and mono[tris(hydroxymethyl)aminomethane] phosphate (Trizma) were determined at (25.0 ± 0.1) °C and I = 0.1 mol dm-3 (KNO3) by potentiometric pH titration in pure water and different hydroorganic solvent media. The organic solvents used were methanol and ethanol as amphiprotic hydrogen bond acceptor−donor (HBA-D) solvents, N,N-dimethylformamide (DMF), dimethy1 sulfoxide, acetone, and dioxane as hydrogen bond acceptor solvents, and acetonitrile as an HBA−HBD solvent. The ESAB2M computer program was used to refine the initial estimates of the apparent second-stage dissociation constants of the four zwitterionic buffers studied. pka2* values change with increasing organic content of the solvent mixture. The results obtained are discussed in terms of average macroscopic properties of the mi...

The apparent second-stage dissociation constants of 3-(N-morpholino)propanesulfonic acid, 3-[(1,1-dimethyl-2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid, and N-(2-hydroxyethyl)piperazine-N‘-(2-hydroxypropanesulfonic acid) were determined at (25.0 ± 0.1) °C and I = 0.1 mol dm-3 (KNO3) by potentiometric pH titration in pure water and different hydroorganic solvent media. The organic solvents used were methanol, ethanol as amphiprotic hydrogen bond acceptor−donor (HBA-D) solvents, N,N-dimethylformamide, dimethyl sulfoxide, acetone, dioxane as hydrogen bond acceptor solvents, and acetonitrile as (HBA-HBD) solvent. The ESAB2M computer program was used to refine the initial estimates of the apparent second-stage dissociation constants of the three zwitterionic buffers studied. pKa2* values change with increasing organic content of the solvent mixture. The results obtained are discussed in terms of average macroscopic properties of the mixed solvents. The implications of the results with regard to specific...

The apparent dissociation constants of 3-[N-(tris(hydroxy methyl)methyl)amino]-2-hydroxypropane sulfonic acid (TAPSO), 3-[N,N-bis(2-hydroxyethyl)amino]-2-hydroxypropane sulfonic acid (DIPSO), and 3...

The apparent dissociation constants of 3-(cyclohexylamino)-1-propanesulfonic acid (CAPS) and 3-(cyclohexylamino)-2-hydroxy-1-propanesulfonic acid (CAPSO) were determined at (25.00 ± 0.10) °C and I = 0.1 mol dm-3 KNO3 by potentiometric pH titration in pure water and different hydroorganic solvent media. The organic solvents used were methanol, ethanol, N,N-dimethylformamide, dimethyl sulfoxide, acetonitrile, acetone, and dioxane. Initial estimates of the apparent dissociation constant values of the two zwitterionic amino propanesulfonic acid buffers studied have been refined with the ESAB2M computer program. pKa2* values change with an increase in the concentration of organic solvent. The results obtained are discussed in terms of average macroscopic properties of the mixed solvents and the possible variation in microheterogenity of the solvation shells around the solute.

The apparent dissociation constants of malic acid (hydroxybutanedioic acid), tartaric acid (2,3-dihydroxybutanedioic acid), phthalic acid (1,2-benzenedicarboxylic acid), and succinic acid (butane-1,4-dioic acid) were determined at 25 °C and ionic strength I = 0.10 mol dm-3 KNO3 by potentiometric pH titration in pure water and water + methanol, water + ethanol, water + N,N-dimethylformamide, water + dimethyl sulfoxide, and water + acetonitrile. pKa values increase with an increase in the concentration of the organic solvents. These results are discussed in terms of solvent characteristics. Solvent basicity and stabilization of the conjugate acid free base by hydrogen-bonding interactions in hydroorganic solvent media relative to pure aqueous media as well as proton−solvent interaction play an important role in the acid dissociation equilibrium.

Potentiometric measurements have been made at 25.0±0.1 o C and ionic strength I=0.1 mol dm -3 KNO 3 for the interaction of adenosine 5'-mono-, 5'-di-, and 5'-triphosphates (AMP, ADP, and ATP) and Co(II) with biologically important secondary ligand zwitterionic buffers N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid (BES), N-[tris(hydroxymethyl)methyl]-2-aminoethanesulfonic acid (TES), N,N-bis(2-hydroxyethyl)glycine (Bicine), and N-[tris(hydroxymethyl)methyl]-3-aminopropanesulfonic acid (TAPS) in a 1:1:1: ratio and the formation of various 1:1:1 mixed ligand complex species inferred from the potentiometric pH titration curves. Initial estimates of the formation constants of the resulting species and the acid dissociation constants of the resulting species and the acid dissociation constants of AMP, ADP, ATP, and secondary ligands have been refined with the SUPERQUAD computer program

Potentiometric equilibrium measurements have been made at (25±0.1) o C and ionic strength I=0.1 mol dm -3 KNO 3 for the interaction of adenosine 5' mono-, 5'-di-, and 5'-triphosphate (AMP, ADP, and ATP) and Cu(II) with biologically important secondary ligand acids (malic, maleic, succinic, tartaric, and oxalic acids) in a 1:1:1 ratio and the formation of various 1:1:1 mixed ligand complex species inferred from the potentiometric pH titration curves. Initial estimates of the formation constants of the resulting species and the acid dissociation constants of AMP, ADP, ATP, and secondary ligand acid have been refined with the SUPERQUAD computer program

The dissociation constant of acetic acid, benzoic acid, 3-phenylpropenoic acid, 2-methylpropionic acid, and pentanoic acid were determined at 25.0 °C (I = 0.1 mol dm -3 KNO 3 ) by potentiometric pH titration in pure water and water + methanol, water + ethanol, water + dimethylformamide, water + dimethyl sulfoxide, and water + acetonitrile. pK a values increase with an increase in the concentration of the organic compounds. These results are discussed in terms of solvent characteristics. Solvent basicity and stabilization of the conjugate acid free base by hydrogen-bonding interactions in hydroorganic solvent media relative to pure aqueous media as well as proton-solvent interaction play an important role in the acid dissociation equilibrium.

The second-stage dissociation constants of N,N-bis(2-hydroxyethyl)glycine (bicine) rvere determined at 25.00±0.02 o C by potentiometric pH titration in pure water and different mixed solvent mixtures (methanol, ethanol, N,N-dimethylformamide, dimethyl sulfoxide, acetone, and dioxane). It is observed that the pK a2 , value is slightly influenced as the solvent is enriched in methanol or ethanol and remains practically constant in the presence of different amounts of DMF and DMSO. A pronounced change in the pK a2 , value is observed as the solvent is enriched in acetone or dioxane. These results are discussed in terms of various solvent characteristics. It is concluded that the electrostatic effect has only a relatively small influence on the dissociation equilibrium of the imino group (-NH + )

The second-stage dissociation constant values of N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid (BES) were determined at 25±0.1 o C by potentiometric pH titration in different solvent mixtures. The organic solvents used are methanol, ethanol, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetone, and dioxane. The ionization of BES depends on both the proportion and the nature of the organic cosolvent used. It is observed that the pK a2 value is slightly influenced as the solvent is enriched in methanol and ethanol and remains practically constant in the presence of different amounts of DMF and DMSO