It has been suggested that this article or section be merged with ligand. (Discuss)

For ligand in the chemical sense, see Ligand.

In biochemistry, a ligand is an effector, a molecule that binds to a site on a macromolecule's surface by intermolecular forces, thereby changing the chemical conformation of the macromolecule. Once a molecule's conformation has changed, its ability to function in other chemical reactions is altered. This binding is usually a reversible reaction, i.e. it can be undone. Actual coordinate covalent bonds between a ligand and its target molecule are rare in biological systems. Ligands include substrates, inhibitors, activators, and neurotransmitters. Wikipedia does not have an article with this exact name. ... It has been suggested that this article or section be merged with Ligand (biochemistry). ... It has been suggested that this article or section be merged with Ligand (biochemistry). ... Biochemistry is the study of the chemistry of life, a bridge between biology and chemistry that studies how complex chemical reactions give rise to life. ... An effector is a small molecule that binds to a protein and thereby alters the activity of that protein. ... In general, a molecule is the smallest particle of a pure chemical substance that still retains its composition and chemical properties. ... A macromolecule is a molecule of high relative molecular mass, the structure of which essentially comprises the multiple repetition of units derived, actually or conceptually, from molecules of low relative molecular mass. ... Intermolecular forces are electromagnetic forces which act between molecules or between widely separated regions of a macromolecule. ... In chemistry, a chemical conformation is the spatial arrangement of atoms in a molecule. ... A chemical reaction is a process that results in the interconversion of chemical substances [1]. The substance or substances initially involved in a chemical reaction are called reactants. ... A reversible reaction is a chemical reaction that may be reversed. ... A coordinate covalent bond (also known as dative covalent bond) is a special type of covalent bond in which the shared electrons come from one of the atoms only. ... The word substrate can mean the following: In biochemistry, a substrate is a molecule which is acted upon by an enzyme. ... An inhibitor is a type of effector (biology) that decreases or prevents a chemical reaction. ... Activator may mean: Activator (proteomics), a type of effector that increases the rate of enzyme mediated reactions Activator (genetics), a DNA-binding protein that regulates one or more genes by increasing the rate of transcription Sega Activator, a motion-sensing controller for the Sega Genesis Activator (day after partying), The... Neurotransmitters are chemicals that are used to relay, amplify and modulate electrical signals between a neuron and another cell. ...

Whether or not the ligand actually binds at a metal site is irrelevant, as opposed to 'ligand' in chemical sense. 'Ligand' is probably originally a carryover term from the large number of binding studies on oxygen transport proteins, such as hemoglobin, in which the ligand does indeed bind at a metal site. In the case of hemoglobin oxygen acts as a ligand. Hot metal work from a blacksmith Look up Metal in Wiktionary, the free dictionary In chemistry, a metal (Greek: Metallon) is an element that readily forms ions (cations) and has metallic bonds, and metals are sometimes described as a lattice of positive ions (cations) surrounded by a sea of delocolised... It has been suggested that this article or section be merged with Ligand (biochemistry). ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... 3-dimensional structure of hemoglobin. ...

Protein ligands are studied in structural biology and metabolomics. Radioactive ligands (radioligands) are used together with positron emission tomography to study the receptor systems of the brain. In biochemistry, a protein ligand is an atom, a molecule or an ion which can bind to a specific site on a protein. ... Structural biology is a branch of molecular biology concerned with the study of the architecture and shape of biological macromolecules--proteins and nucleic acids in particular—and what causes them to have the structures they have. ... Metabolomics is the systematic study of the unique chemical fingerprints that specific cellular processes leave behind - specifically, the study of their small-molecule metabolite profiles The metabolome represents the collection of all metabolites in a biological organism, which are the end products of its gene expression. ... A radioligand is a radioactive biochemical substance that is used to study the receptor systems of the brain. ... Image of a typical positron emission tomography (PET) facility Positron emission tomography (PET) is a nuclear medicine medical imaging technique which produces a three dimensional image or map of functional processes in the body. ... In biochemistry, a receptor is a protein on the cell membrane or within the cytoplasm or cell nucleus that binds to a specific molecule (a ligand), such as a neurotransmitter, hormone, or other substance, and initiates the cellular response to the ligand. ...

In basic biology, ligands attach to receptors as a way of cytoplasmic signaling in a cell. The two main types of receptors that these ligands can attach to are soluble cytoplasmic proteins or transmembrane receptors. An example of a cytoplasmic protein is a steroid receptor, where the ligand must be hydrophobic to get through the cell membrane, then attach to their desired protein within the cytoplasm. Transmembrane receptors are integral membrane proteins, which reside and operate typically within a cells plasma membrane, but also in the membranes of some subcellular compartments and organelles. ...

Receptor/Ligand binding affinity

The interaction of most ligands with their binding sites can be characterized in terms of a binding affinity. In general, high affinity ligand binding results from greater intermolecular force between the ligand and its receptor while low affinity ligand binding involves less intermolecular force between the ligand and its receptor. In general, high affinity binding involves a longer residence time for the ligand at its receptor binding site than is the case for low affinity binding. High affinity binding of ligands to receptors is often physiologically important when some of the binding energy can be used to cause a conformational change in the receptor, resulting in altered behavior of an associated ion channel or enzyme. Ligand-gated ion channel is a broad term that refers to any ion channel that is gated (i. ... Ribbon diagram of the enzyme TIM. TIM is catalytically perfect, meaning its conversion rate is limited, or nearly limited to its substrate diffusion rate. ...

Two agonists with similar binding affinity

A ligand that can bind to a receptor, alter the function of the receptor and trigger a physiological response is called an agonist for that receptor. Agonist binding to a receptor can be characterized both in terms of how much physiological response can be triggered and the concentration of the agonist that is required to produce the physiological response. High affinity ligand binding implies that a relatively low concentration of a ligand is adequate to maximally occupy a ligand binding site and trigger a physiological response. Low affinity binding implies that a relatively high concentration of a ligand is required before the binding site is maximally occupied and the maximum physiological response to the ligand is achieved. In the example shown to the right, two different ligands bind to the same receptor binding site. Only one of the agonists shown can maximally stimulate the receptor and it can be defined as a "full agonist". An agonist that can only partially activate the physiological response is called a "partial agonist". Ligands that bind to a receptor but fail to activate the physiological response are receptor "antagonists". In this example, the concentration at which the full agonist (red curve) can half-maximally activate the receptor is about 5 x 10^-9 Molar (nM = nanomolar). Agonists activate receptors. ... Agonists activate receptors. ... Agonists An agonist is a substance that binds to a receptor and triggers a response in the cell. ... In chemistry, concentration is the measure of how much of a given substance there is mixed with another substance. ... Antagonists In medicine and biology, a receptor antagonist is a substance that inhibits the normal physiological function of a receptor. ... In chemistry, concentration is the measure of how much of a given substance there is mixed with another substance. ... Nano is a noun Name for an Apple Brand Ipod available in 2GB and 4GB memory sizes whose purpose is for storing and playing music. ...

Two ligands with different receptor binding affinity.

In the example shown to the left, ligand binding curves are shown for two ligands with different binding affinities. Ligand binding is often characterized in terms of the concentration of ligand at which half of the receptor binding sites are occupied (k_d). The ligand illustrated by the red curve has a higher binding affinity and smaller k_d than the ligand illustrated by the green curve. If these two ligands were present at the same time, more of the higher affinity ligand would be bound to the available receptor binding sites. This is how carbon monoxide can compete for oxygen in binding to hemoglobin, resulting in carbon monoxide poisoning. Image File history File links Agonists. ... Image File history File links Agonists. ... Carbon monoxide, chemical formula CO, is a colorless, odorless, tasteless, flammable and highly toxic gas. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... Carbon monoxide toxicity is due to two main mechanisms: CO binds to hemoglobin and decreases the oxygen content of blood; this results in acute tissue hypoxic injury CO binds to mitochondrial cytochrome oxidase and impairs oxidative phosphorylation and causes cell damage Carbon monoxide (CO) binds very strongly to the iron...

See also

• Allosteric regulation

In biochemistry, allosteric regulation is the regulation of an enzyme or protein by binding an effector molecule at the proteins allosteric site (that is, a site other than the proteins active site). ...

References

• Ligand binding to hormone receptors in Endocrinology: An Integrated Approach by Stephen Nussey and Saffron Whitehead (2001) Published by BIOS Scientific Publishers Ltd. ISBN 1859962521.
• Molecular Recognition Processes in Molecular Biology of the Cell 3rd edition (1994) by by Bruce Alberts, Dennis Bray, Julian Lewis, Martin Raff, Keith Roberts and James D. Watson. See Figure 3-9, Equilibrium ligand binding.