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 ?
Ligand applied to the European Agency for the Evaluation of Medicinal Products (EMEA) via the centralized procedure to market ONZAR for the treatment of persistent or recurrent CTCL in patients whose malignant cells express the p55 (CD25) component of the IL-2 receptor and who have received one or more prior systemic therapies.
As it turns out, however, lymphocytes aren't the only tissues that produce Fas ligand.
We are very pleased that LGD 4665, a novel, second generation, orally active thrombopoietin mimetic is advancing to human clinical trials," said Andres Negro-Vilar, MD, PhD, Executive Vice President, R&D and Chief Scientific Officer, Ligand Pharmaceuticals.
Under the terms of the asset purchase agreement, Ligand will receive cash of approximately $35 million, net of fees, expenses, and existing indebtedness.
In addition to existing royalty obligations, King will pay Ligand a 15 percent royalty during the first 20 months after the closing date.
Blissenbach stated, "We have now sold our two commercial operations for aggregate cash consideration of $518 million, and have also retained a significant royalty participation in AVINZA -- which we believe will provide extraordinary value to Ligand as a result of the excellent sales capabilities of King Pharmaceuticals.
Although Ligand believes these suits are without merit, the Company is pleased to put the uncertainty, expense, and management time drain of the class action and derivative litigation behind it and believes that the decision to settle is in the best interests of its shareholders," said David E.
Collectively, the results presented at ASCO this year further strengthen, with the use of selective biomarker analysis, the potential benefit of Targretin therapy added to chemotherapy in a first line setting, or as monotherapy in third line, heavily pretreated patients, in an important group of NSCLC patients," said Andres Negro-Vilar, Executive Vice President, R&D and Chief Scientific Officer, Ligand Pharmaceuticals.
Eltrombopag was discovered as a result of a research collaboration between GlaxoSmithKline and Ligand Pharmaceuticals.
SAN DIEGO -- Ligand Pharmaceuticals Incorporated (Pink Sheets:LGND) announced today that it has signed an agreement with Organon USA, Inc.
SAN DIEGO -- Ligand Pharmaceuticals Incorporated (Pink Sheets:LGND) announced today that it has filed a Form S-1 Registration Statement with the Securities and Exchange Commission for its existing employee stock plans: the employee and director stock incentive plan and the employee stock purchase plan.

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