Ligand

A Ligand is a molecule or ion that binds to a target structure through molecular interactions, typically to a metal atom in coordination complexes or to a biomolecule in biological systems.

• AKA: Binding Molecule, Complexing Agent.
• Context:
  • It can typically form Coordinate Bonds with metal centers in coordination chemistry.
  • It can typically bind to Protein Binding Sites through non-covalent interactions.
  • It can typically donate Electron Pairs as a Lewis base in metal complexes.
  • It can typically exhibit Binding Affinity for specific target molecules.
  • It can typically induce Conformational Changes in target biomolecules.
  • It can typically activate Neurotransmitter Receptors when serving as neurotransmitters or receptor agonists.
  • ...
  • It can often bind through Hydrogen Bonds, van der Waals forces, or electrostatic interactions.
  • It can often display Binding Specificity for particular binding sites.
  • It can often compete with other ligands for binding site occupancy.
  • It can often be characterized by Dissociation Constants and binding kinetics.
  • It can often serve as Antigen in antibody tests for diagnostic purposes.
  • ...
  • It can range from being a Monodentate Ligand to being a Polydentate Ligand, depending on its coordination number.
  • It can range from being a High-Affinity Ligand to being a Low-Affinity Ligand, depending on its binding strength.
  • It can range from being a Small Molecule Ligand to being a Macromolecular Ligand, depending on its molecular size.
  • ...
  • It can be classified by Denticity as monodentate, bidentate, or multidentate ligands.
  • It can be characterized by Ligand Cone Angle in coordination complexes.
  • It can participate in Ligand Exchange Reactions with varying kinetic rates.
  • It can modulate Biological Activity when binding to receptors or enzymes.
  • It can associate with Binding Proteins for transport, storage, or regulatory functions.
  • ...
• Examples:
  • Coordination Chemistry Ligands, such as:
    • Water, a monodentate ligand forming aqua complexes.
    • Ammonia, a neutral ligand in ammine complexes.
    • Ethylenediamine, a bidentate ligand forming chelate complexes.
    • EDTA, a hexadentate ligand for metal chelation.
    • Porphyrin Ring ligands in chlorophyll, coordinating magnesium ions.
  • Biological Ligands, such as:
    • Hormone Ligands, such as:
      • Insulin, binding to insulin receptors.
      • Glucagon-Like Peptide-1 (GLP-1) Hormone, binding to GLP-1 receptors.
    • Neurotransmitter Ligands, such as:
      • Acetylcholine, binding to cholinergic receptors.
      • Dopamine, binding to dopamine receptors.
    • Drug Ligands, such as:
      • Receptor Agonists, activating target receptors.
      • Enzyme Inhibitors, blocking enzyme active sites.
  • Endogenous Ligands, such as:
    • ATP, binding to ATP-binding proteins.
    • Calcium Ions, binding to calcium-binding proteins.
    • Lipids, binding to apolipoprotein B for lipid transport.
    • Antigens, binding to antibody in antibody tests.
  • ...
• Counter-Example(s):
  • Substrates, which undergo chemical transformation rather than just binding.
  • Cofactors, which are permanently associated with enzymes rather than reversibly binding.
  • Structural Proteins, which provide mechanical support rather than binding interactions.
  • Solvent Molecules, which surround but don't specifically bind to targets.
• See: Ligand Cone Angle, Lewis Acids and Bases, Opioid Receptor, Bond Order, Receptor (Biochemistry), Coordination Complex, Binding Affinity, Dissociation Constant, Chelation, Molecular Recognition, Neurotransmitter Receptor, Binding Protein, Chlorophyll, Antibody Test, Apolipoprotein B, Receptor Agonist.

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References

2023

• HTTP://chat.openai.com/chat
  • A ligand is a molecule that binds to and forms a complex with a larger biomolecule, often a protein. Ligands can be atoms, ions, or molecules, and are usually characterized by their ability to bind to a specific site on a target protein, such as an enzyme or receptor. Ligands can be endogenous (produced naturally in the body) or exogenous (introduced into the body from an external source).

    Related concepts include:

    • Agonist: a type of ligand that activates a receptor by mimicking the effects of an endogenous ligand.
    • Antagonist: a type of ligand that binds to a receptor without activating it, blocking the action of endogenous ligands or other agonists.
    • Enzyme inhibitor: a type of ligand that binds to an enzyme, blocking its activity.
    • Substrate: a type of ligand that binds to an enzyme and undergoes a chemical reaction.
    • Receptor: a large protein molecule that binds to a ligand and initiates a cellular response.

2023

• (Wikipedia, 2023) ⇒ https://en.wikipedia.org/wiki/ligand Retrieved:2023-2-27.
  • In coordination chemistry, a ligandis an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's electron pairs, often through Lewis bases. The nature of metal–ligand bonding can range from covalent to ionic. Furthermore, the metal–ligand bond order can range from one to three. Ligands are viewed as Lewis bases, although rare cases are known to involve Lewis acidic "ligands".

    Metals and metalloids are bound to ligands in almost all circumstances, although gaseous "naked" metal ions can be generated in a high vacuum. Ligands in a complex dictate the reactivity of the central atom, including ligand substitution rates, the reactivity of the ligands themselves, and redox. Ligand selection requires critical consideration in many practical areas, including bioinorganic and medicinal chemistry, homogeneous catalysis, and environmental chemistry.

    Ligands are classified in many ways, including: charge, size (bulk), the identity of the coordinating atom(s), and the number of electrons donated to the metal (denticity or hapticity). The size of a ligand is indicated by its cone angle.

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