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Related Concept Videos

Complexation Equilibria: Factors Influencing Stability of Complexes01:09

Complexation Equilibria: Factors Influencing Stability of Complexes

In complexation reactions, metal cations are the electron pair acceptors, and the ligands are the electron pair donors. The stability of the metal complexes depends primarily on the complexing ability of the central metal ion and the nature of the ligands. Generally, the complexing ability of the metal ion depends on the size and charge of the ion. As the metal ion size increases, the stability of the metal complexes decreases, provided that the valency of the metal ion and the ligands remain...
Ladder Diagrams: Complexation Equilibria01:07

Ladder Diagrams: Complexation Equilibria

Ladder diagrams are useful for evaluating equilibria involving metal-ligand complexes. The vertical scale of the ladder diagram represents the concentration of unreacted or free ligand, pL. The horizontal lines on the scale depict the log of stepwise formation constants for metal-ligand complexes and indicate the dominant species in all the regions.
The formation constant, K1, for the formation of Cd(NH3)2+ complex from cadmium and ammonia is 3.55 × 102. Log K1 (i.e. pNH3) is 2.55, and...
Extraction: Advanced Methods00:56

Extraction: Advanced Methods

Metal ions can be separated from one another by complexation with organic ligands–the chelating agent– to form uncharged chelates. Here, the chelating agent must contain hydrophobic groups and behave as a weak acid, losing a proton to bind with the metal. Since most organic ligands used in this process are insoluble or undergo oxidation in the aqueous phase, the chelating agent is initially added to the organic phase and extracted into the aqueous phase. The metal-ligand complex is formed in...
Complexation Equilibria: The Chelate Effect01:19

Complexation Equilibria: The Chelate Effect

In complexation reactions, metal atoms or cations interact with ligands to form donor-acceptor adducts called metal complexes. Ligands that bind through one donor site are monodentate, ligands with two donor sites are bidentate, and those with more than two donor sites are polydentate ligands. For example, ethylene diamine is a bidentate ligand that binds through two nitrogen donor atoms, forming a five-membered ring. EDTA is a polydentate ligand that binds through four oxygen and two nitrogen...
Calmodulin-dependent Signaling01:16

Calmodulin-dependent Signaling

Calmodulin (CaM) is a calcium-binding protein in eukaryotes that controls various calcium-regulated cellular processes. It has four calcium-binding sites that bind calcium to form the calcium-calmodulin ( Ca2+-CaM) complex. GPCR stimulation increases the calcium levels in the cells that bind to CaM and induces a conformational change.
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...
Structure of Cadherins01:25

Structure of Cadherins

The cadherins were one of the first cell adhesion molecules discovered; the term “cadherins”   is based on their calcium-dependent adhering properties. The first cadherins discovered on the epithelial, neuronal, and placental cells were named E-cadherin, P-cadherin, and N-cadherin, respectively. These classical cadherins share sequence and structural similarities. Other cadherins, including those involved in cell signaling, are grouped into non-classical cadherins. This diversity of cadherins...

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Related Experiment Video

Updated: May 23, 2026

An Anaerobic Biosensor Assay for the Detection of Mercury and Cadmium
09:33

An Anaerobic Biosensor Assay for the Detection of Mercury and Cadmium

Published on: December 17, 2018

Labile complexes facilitate cadmium uptake by Caco-2 cells.

L Verheyen1, F Degryse, T Niewold

  • 1Division of Soil and Water Management, K.U.Leuven, Kasteelpark Arenberg 20, Box 2459, 3001 Heverlee, Belgium. Liesbeth.Verheyen@ees.kuleuven.be

The Science of the Total Environment
|April 17, 2012
PubMed
Summary

Labile cadmium complexes enhance metal bioavailability in intestinal cells, contrary to the Free Ion Activity Model. This suggests metal speciation significantly impacts uptake, with complexes potentially alleviating diffusion limitations.

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Using Caco-2 Cells to Study Lipid Transport by the Intestine
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Using Caco-2 Cells to Study Lipid Transport by the Intestine

Published on: August 20, 2015

Related Experiment Videos

Last Updated: May 23, 2026

An Anaerobic Biosensor Assay for the Detection of Mercury and Cadmium
09:33

An Anaerobic Biosensor Assay for the Detection of Mercury and Cadmium

Published on: December 17, 2018

Using Caco-2 Cells to Study Lipid Transport by the Intestine
07:00

Using Caco-2 Cells to Study Lipid Transport by the Intestine

Published on: August 20, 2015

Area of Science:

  • Environmental Chemistry
  • Toxicology
  • Cell Biology

Background:

  • The Free Ion Activity Model (FIAM) posits that only free metal ions are bioavailable.
  • However, research indicates labile metal complexes can enhance bioavailability, particularly when uptake is diffusion-limited.
  • The role of these complexes in intestinal absorption remains under investigation.

Purpose of the Study:

  • To assess the bioavailability of labile cadmium (Cd) complexes using Caco-2 cells, a model for intestinal absorption.
  • To investigate the influence of Cd speciation on its uptake by intestinal cells.
  • To determine if labile Cd complexes enhance metal bioavailability by overcoming diffusion limitations.

Main Methods:

  • Utilized Caco-2 cells as an in vitro model for intestinal absorption.
  • Measured Cd uptake at varying Cd(2+) concentrations (1 nM and 10 μM) and in the presence of synthetic ligands like EDTA.
  • Employed the Diffusive Gradient in Thin Films (DGT) technique to measure Cd diffusion flux in solution.

Main Results:

  • At low Cd(2+) concentrations (1 nM), Cd complexes contributed significantly to cellular uptake, comparable to free Cd(2+).
  • At high Cd(2+) concentrations (10 μM), the contribution of Cd complexes to uptake was substantially reduced.
  • Cd intake increased with higher dissociation rates of Cd complexes and correlated with DGT-measured Cd diffusion flux.
  • Cellular Cd uptake fluxes were accurately predicted by models assuming diffusion-limited uptake of free Cd(2+) ions.

Conclusions:

  • Cadmium speciation critically affects its uptake by intestinal cells.
  • Bioavailability is not solely determined by free Cd(2+) concentration; labile Cd complexes can enhance uptake.
  • Labile Cd complexes likely improve metal bioavailability by mitigating diffusion limitations to the cell surface.