ligand

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ligand

(lĭg`ənd), charged or uncharged molecule with one or more unshared pairs of electrons that can attach to a central metallic atomatom
[Gr.,=uncuttable (indivisible)], basic unit of matter; more properly, the smallest unit of a chemical element having the properties of that element. Structure of the Atom
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 or ionion,
atom or group of atoms having a net electric charge. Positive and Negative Electric Charges

A neutral atom or group of atoms becomes an ion by gaining or losing one or more electrons or protons.
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 to form an aggregate known as a complex ion (see chemical bondchemical bond,
mechanism whereby atoms combine to form molecules. There is a chemical bond between two atoms or groups of atoms when the forces acting between them are strong enough to lead to the formation of an aggregate with sufficient stability to be regarded as an
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). Some ligands that share electrons with metals form very stable complexes. Some common bases that act as ligands are water and ammonia molecules and halide, hydroxide, acetate, cyanide, thiocyanate, and nitrite anionsanion
, atom or group of atoms carrying a negative charge. The charge results because there are more electrons than protons in the anion. Anions can be formed from nonmetals by reduction (see oxidation and reduction) or from neutral acids (see acids and bases) or polar compounds
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. These ligands are monofunctional, i.e., they are attached by one unshared pair of electrons during complexing. Polyfunctional ligands, which bind to the metal ion with two or more pairs of electrons, are called chelates (see chelating agentschelating agents
. Certain organic compounds are capable of forming coordinate bonds (see chemical bond) with metals through two or more atoms of the organic compound; such organic compounds are called chelating agents.
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). Ethylenediamine-tetraacetate, a commonly used chelating compound, has six pairs of electrons to bind to metal ions. Electron-donating functional groups containing nitrogen, oxygen, sulfur, phosphorous, or carbon may act as ligands in complex biological systems. For example, in enzymes that need complexed metal ions to function, mercapto (sulfur-containing) groups and amino (nitrogen-containing) groups act as chelating agents; these groups fix the metal ion in a specific position. Other biologically important molecules, such as chlorophyll, vitamin B12, and heme, also have nitrogen-containing groups that donate electrons and have a chelating function.

ligand

[′lī·gənd]
(chemistry)
The molecule, ion, or group bound to the central atom in a chelate or a coordination compound; an example is the ammonia molecules in [Co(NH3)6]3+.
References in periodicals archive ?
In addition, endogenous ligands generated during joint inflammation can activate TLR pathway and perpetuate joint damage.
Using a test set of 33 GPCRs for which the endogenous ligand is already known, 91% of these GPCRs can be detected using the SNAP UFA(TM) technology.
Synaptic will screen orphan GPCRs in the SNAP UFA(TM) in order to identify "Hits" from its endogenous ligand library.
Other proliferating T cells upregulate cholesterol biosynthesis, however Lycera's data show that this effect is selectively important in Th17 cells by providing endogenous ligands for RORgamma, thus enforcing commitment of naive T cells to the Th17 lineage.
LXR activation by endogenous ligands, oxysterols (oxidized cholesterol) or by synthetic agonists, initiates a cascade of cellular events that both increase "reverse cholesterol transport," thereby removing excess cholesterol from the body, and suppress inflammation.
Regulation of FXR with endogenous ligands, such as chenodeoxycholic acid, leads to a series of transcriptional responses that regulate triglyceride, cholesterol and bile acid metabolism.
This target-class focused chemical library is composed of small molecules which represent mimics of conserved regions of secondary structures of endogenous ligands which are likely to interact with G-protein coupled receptors (GPCRs).
CRL's de-novo approach involves the design and synthesis of library templates that mimic selected secondary structures of conserved regions of endogenous ligands applicable for various GPCR sub-families.
announced today that it has defined the entire repertoire of G-protein coupled receptors, which respond to endogenous ligands (endoGPCRs) in humans and mice.
The platform has two configurations: High Resolution Screening (HRS), which can be used to screen non-human-derived complex mixtures for active molecules against drug targets; and Orphan Target Screening (OTS), which can be used to screen human samples (blood, urine, tissue extracts) against orphan targets to identify endogenous ligands.
Branchek will discuss Synaptic's SNAP UFA(TM) technology platform, which rapidly and cost-effectively identifies the endogenous ligands for orphan GPCRs.
Synaptic Pharmaceutical Corporation (Nasdaq: SNAP) today announced that the Company's scientists will present a number of papers including, "Universal Functional Assay for Identifying Endogenous Ligands for G Protein-Coupled Receptors (GPCRs)," and three additional papers concerning receptors de-orphanized using the SNAP UFA(TM) technology platform to the 30th Annual Society for Neuroscience meeting.

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