Related Experiment Video
Updated: Mar 19, 2026
12:38
Titration ELISA as a Method to Determine the Dissociation Constant of Receptor Ligand Interaction
Published on: February 15, 2018
20.9K
Competitive counterion complexation allows the true host : guest binding constants from a single titration by ionic
Márcia Pessêgo1, Nuno Basílio1, M Carmen Muñiz2
1Laboratório Associado para a Química Verde (LAQV), REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, 2829-516 Monte de Caparica, Portugal. m.pessego@fct.unl.pt.
Organic & Biomolecular Chemistry
|June 10, 2016
Summary
This study introduces a method to accurately measure host-guest binding constants by accounting for counterion complexation. This approach overcomes experimental challenges, revealing true binding constants and complex stoichiometry.
Area of Science:
- Supramolecular Chemistry
- Analytical Chemistry
Background:
- Ionic hosts often ignore counterion competitive complexation, affecting guest binding constants.
- Experimental results are frequently dependent on guest concentration and added salts.
- Existing methods lack accuracy due to unaddressed background complexation.
Purpose of the Study:
- To present a method that accounts for counterion competitive complexation in host-guest binding studies.
- To enable accurate determination of true binding constants and complex stoichiometry.
- To overcome limitations of traditional titration experiments.
Main Methods:
- Incorporating counterion competitive complexation into binding models.
- Utilizing single titration experiments to determine binding constants and stoichiometry.
- Applying displacement assays with competitive and competitive-cooperative models.
Main Results:
- A method was developed to accurately determine host-guest binding constants.
- True binding constants and complex stoichiometry (1:1:1 host:guest:counterion) were obtained.
- The method proved effective in both titration and displacement assays.
Conclusions:
- Considering counterion competitive complexation is crucial for accurate host-guest binding studies.
- The proposed method simplifies experiments and provides reliable data.
- This approach enhances the understanding of supramolecular complex formation.
Related Concept Videos
00:43Complexometric Titration: Ligands
2.6K
Different monodentate and polydentate ligands are used as complexing agents in complexometric titration reactions. The formation of complexes by mono- and bidentate ligands involves two or more intermediate steps, limiting their use as complexing agents. In comparison, polydentate ligands can form complexes with metal ions in a single-step process, facilitating sharper end points. This means polydentate ligands, such as amino carboxylic acid derivatives, are most commonly employed in...
2.6K
01:23Complexation Equilibria: Overview
1.6K
Complexation reactions take place when dative or coordinate covalent bonds form between metal ions and ligands. The compounds formed in these reactions are called coordination compounds. The number of bonds formed between the metal ion and the ligands is called its coordination number. Generally, most metal ions in an aqueous solution are solvated by water molecules and thus exist as aqua complexes.
The equilibrium constant of the complexation reaction is represented as the formation constant...
The equilibrium constant of the complexation reaction is represented as the formation constant...
1.6K
01:26EDTA: Auxiliary Complexing Reagents
1.5K
EDTA titrations are usually carried out in highly basic conditions, where the fully deprotonated form of EDTA, Y4−, actively complexes with the free metal ions in the solution. Several metal ions precipitate as hydrous oxide (hydroxides, oxides, or oxyhydroxides) under these conditions, lowering the concentration of free metal ions in the solution. For this reason, auxiliary complexing agents or ligands such as ammonia, tartrate, citrate, or triethanolamine are used in EDTA titrations to...
1.5K
00:39Complexometric Titration: Overview
12.9K
Complexometric titration involves the formation of a complex by reacting a metal ion with one or more ligands. A visual indicator often detects the end point of a complexometric titration. It is added to the metal solution before the titration, forming a stable metal–indicator complex and imparting color to the solution. As the titration approaches the equivalence point, the excess of the added ligand displaces the indicator from the metal–indicator complex, releasing the free...
12.9K
03:45Formation of Complex Ions
26.6K
A type of Lewis acid-base chemistry involves the formation of a complex ion (or a coordination complex) comprising a central atom, typically a transition metal cation, surrounded by ions or molecules called ligands. These ligands can be neutral molecules like H2O or NH3, or ions such as CN− or OH−. Often, the ligands act as Lewis bases, donating a pair of electrons to the central atom. These types of Lewis acid-base reactions are examples of a broad subdiscipline called coordination...
26.6K
02:18The Equilibrium Binding Constant and Binding Strength
15.5K
The equilibrium binding constant (Kb) quantifies the strength of a protein-ligand interaction. Kb can be calculated as follows when the reaction is at equilibrium:
15.5K