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Protonation equilibria of biologically active ligands in mixed aqueous organic solvents.

El-Sherif AA, Shoukry MM, Abd Elkarim AT, Barakat MH - Bioinorg Chem Appl (2014)

Bottom Line: The review is mainly concerned with the protonation equilibria of biologically active ligands like amino acids, peptides, DNA constituents, and amino acid esters in nonaqueous media.Equilibrium concentrations of proton-ligand formation as a function of pH were investigated.Also, thermodynamics associated with protonation equilibria were also discussed.

View Article: PubMed Central - PubMed

Affiliation: Chemistry Department, Faculty of Science, Cairo University, Giza, Egypt ; Department of Chemistry, Faculty of Arts and Science, Northern Border University, Rafha, Saudi Arabia.

ABSTRACT
The review is mainly concerned with the protonation equilibria of biologically active ligands like amino acids, peptides, DNA constituents, and amino acid esters in nonaqueous media. Equilibrium concentrations of proton-ligand formation as a function of pH were investigated. Also, thermodynamics associated with protonation equilibria were also discussed.

No MeSH data available.


Effect of dioxane on the pKa of inosine and inosine 5′-monophosphate (IMP).
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fig11: Effect of dioxane on the pKa of inosine and inosine 5′-monophosphate (IMP).

Mentions: The protonation constants of inosine and inosine 5′-monophosphate (Figure 10) as representative examples of DNA constituents in different compositions of dioxane-water mixtures reveal the following features (Table 10) [88]: pKa (N1H) of inosine increases linearly with increasing percentage of organic solvent in the medium, Figure 11. This may be correlated with the ability of a solvent of relatively low dielectric constant to increase the electrostatic forces between the proton and the ligand anion and consequently the log⁡10⁡K value increases. The same trend was observed for the log⁡10⁡K's of (N1H) and phosphoric acid (P-OH) groups of IMP, Figure 11. The log⁡10⁡K of the phosphate group in IMP is more affected by replacement of water molecules with dioxane. This is in agreement with the above finding, namely, the existence of hydrogen bonds between water molecules and phosphate ions. Thus, the phosphate ions are easily protonated in going from water to dioxane.


Protonation equilibria of biologically active ligands in mixed aqueous organic solvents.

El-Sherif AA, Shoukry MM, Abd Elkarim AT, Barakat MH - Bioinorg Chem Appl (2014)

Effect of dioxane on the pKa of inosine and inosine 5′-monophosphate (IMP).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4150405&req=5

fig11: Effect of dioxane on the pKa of inosine and inosine 5′-monophosphate (IMP).
Mentions: The protonation constants of inosine and inosine 5′-monophosphate (Figure 10) as representative examples of DNA constituents in different compositions of dioxane-water mixtures reveal the following features (Table 10) [88]: pKa (N1H) of inosine increases linearly with increasing percentage of organic solvent in the medium, Figure 11. This may be correlated with the ability of a solvent of relatively low dielectric constant to increase the electrostatic forces between the proton and the ligand anion and consequently the log⁡10⁡K value increases. The same trend was observed for the log⁡10⁡K's of (N1H) and phosphoric acid (P-OH) groups of IMP, Figure 11. The log⁡10⁡K of the phosphate group in IMP is more affected by replacement of water molecules with dioxane. This is in agreement with the above finding, namely, the existence of hydrogen bonds between water molecules and phosphate ions. Thus, the phosphate ions are easily protonated in going from water to dioxane.

Bottom Line: The review is mainly concerned with the protonation equilibria of biologically active ligands like amino acids, peptides, DNA constituents, and amino acid esters in nonaqueous media.Equilibrium concentrations of proton-ligand formation as a function of pH were investigated.Also, thermodynamics associated with protonation equilibria were also discussed.

View Article: PubMed Central - PubMed

Affiliation: Chemistry Department, Faculty of Science, Cairo University, Giza, Egypt ; Department of Chemistry, Faculty of Arts and Science, Northern Border University, Rafha, Saudi Arabia.

ABSTRACT
The review is mainly concerned with the protonation equilibria of biologically active ligands like amino acids, peptides, DNA constituents, and amino acid esters in nonaqueous media. Equilibrium concentrations of proton-ligand formation as a function of pH were investigated. Also, thermodynamics associated with protonation equilibria were also discussed.

No MeSH data available.