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 to Parkinson's disease, neuroimmunophilin ligands may have application in the treatment of a broad range of other indications, including: spinal cord injury, brain trauma, and peripheral nerve injury, including post-prostatectomy erectile dysfunction and HIV-related sensory neuropathy.
Among other things, there can be no assurance that GPI 1485, or other neuroimmunophilin ligands, or other NAALADase inhibitor compounds will successfully complete preclinical or clinical testing or be granted regulatory approval to be sold and marketed as pharmaceutical products in the United States or elsewhere.
Neuroimmunophilin ligands are a novel class of drugs developed by Guilford that may have the ability to cause nerve growth and repair.
Over the course of our collaboration, we've learned a great deal about our neuroimmunophilin ligands and are committed to the further development and commercialisation of this technology.
After licensing the rights to this technology, Guilford scientists designed a series of novel, proprietary drugs, called neuroimmunophilin ligands, which possessed potent neurotrophic activity but which were not immunosuppressive.
Since this initial discovery, Guilford's neuroimmunophilin ligands have demonstrated neurotrophic activity in a number of animal models of Parkinson's disease and other acute and chronic neurological diseases and conditions.
A large number of patents have been issued to Guilford covering the use and composition of several different classes of neuroimmunophilin ligands.
Previous research has shown that neuroimmunophilin ligands (NILs), a new class of drug candidates, can induce nerve growth and repair in several animal models of acute and chronic neurological disorders, including Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis (ALS), or Lou Gehrig's disease.
Our latest results offer further evidence that our neuroimmunophilin ligands could yield breakthrough disease-modifying therapies for devastating disorders like Parkinson's disease.
Also presented were preclinical study results demonstrating that numerous classes of Guilford's investigational neuroimmunophilin ligands may be effective neuroprotective agents for the treatment of optic nerve injury.
After licensing the rights to this technology to Guilford, our scientists designed a series of novel, proprietary drugs, called neuroimmunophilin ligands, which possessed the neurotrophic properties of FK-506, without any undesired immunosuppressive activity.
In August 1997, Guilford entered into a major collaboration with Amgen to develop and commercialize neuroimmunophilin ligands for multiple target indications, including Parkinson's disease, Alzheimer's disease, stroke, peripheral neuropathies, traumatic brain injuries, traumatic spinal cord injuries, multiple sclerosis, ophthalmic applications, and two additional undisclosed non-neurological indications.