Tetra-amido macrocyclic ligands (TAMLs) constitute a class of macrocyclic ligands. When complexed to metals, TAMLs are proposed as environmentally friendly catalysts. Although never commercialized, iron-TAML complexes catalyze the degradation of pesticides, effluent streams from paper mills, dibenzothiophenes from diesel fuels, and anthrax spores. [1]
In coordination chemistry, a ligand is an ion or molecule 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. 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".
Signal transduction is the process by which a chemical or physical signal is transmitted through a cell as a series of molecular events, most commonly protein phosphorylation catalyzed by protein kinases, which ultimately results in a cellular response. Proteins responsible for detecting stimuli are generally termed receptors, although in some cases the term sensor is used. The changes elicited by ligand binding in a receptor give rise to a biochemical cascade, which is a chain of biochemical events as a signaling pathway.
In biochemistry and pharmacology, receptors are chemical structures, composed of protein, that receive and transduce signals that may be integrated into biological systems. These signals are typically chemical messengers, which bind to a receptor, they cause some form of cellular/tissue response, e.g. a change in the electrical activity of a cell. There are three main ways the action of the receptor can be classified: relay of signal, amplification, or integration. Relaying sends the signal onward, amplification increases the effect of a single ligand, and integration allows the signal to be incorporated into another biochemical pathway. In this sense, a receptor is a protein-molecule that recognizes and responds to endogenous chemical signals. For example, an acetylcholine receptor recognizes and responds to its endogenous ligand, acetylcholine. However, sometimes in pharmacology, the term is also used to include other proteins that are drug targets, such as enzymes, transporters, and ion channels.
Dimethylglyoxime is a chemical compound described by the formula CH3C(NOH)C(NOH)CH3. Its abbreviation is dmgH2 for neutral form, and dmgH for anionic form, where H stands for hydrogen. This colourless solid is the dioxime derivative of the diketone butane-2,3-dione (also known as diacetyl). DmgH2 is used in the analysis of palladium or nickel. Its coordination complexes are of theoretical interest as models for enzymes and as catalysts. Many related ligands can be prepared from other diketones, e.g. benzil.
In coordination chemistry, the first coordination sphere refers to the array of molecules and ions directly attached to the central metal atom. The second coordination sphere consists of molecules and ions that attached in various ways to the first coordination sphere.
NacNac is the name for a class of anionic bidentate ligands. 1,3-Diketimines are often referred to as "HNacNac", a modification of the abbreviation Hacac used for 1,3-diketones. These species can exist as a mixture of tautomers.
Stephen F. Martin is an American chemist and professor of chemistry at The University of Texas at Austin. He is the M. June and J. Virgil Waggoner Regents Chair in Chemistry.
Denticity refers to the number of donor groups in a single ligand that bind to a central atom in a coordination complex. In many cases, only one atom in the ligand binds to the metal, so the denticity equals one, and the ligand is said to be monodentate. Ligands with more than one bonded atom are called polydentate or multidentate. The word denticity is derived from dentis, the Latin word for tooth. The ligand is thought of as biting the metal at one or more linkage points. The denticity of a ligand is described with the Greek letter κ ('kappa'). For example, κ6-EDTA describes an EDTA ligand that coordinates through 6 non-contiguous atoms.
A stability constant is an equilibrium constant for the formation of a complex in solution. It is a measure of the strength of the interaction between the reagents that come together to form the complex. There are two main kinds of complex: compounds formed by the interaction of a metal ion with a ligand and supramolecular complexes, such as host–guest complexes and complexes of anions. The stability constant(s) provide the information required to calculate the concentration(s) of the complex(es) in solution. There are many areas of application in chemistry, biology and medicine.
Dioxygen complexes are coordination compounds that contain O2 as a ligand. The study of these compounds is inspired by oxygen-carrying proteins such as myoglobin, hemoglobin, hemerythrin, and hemocyanin. Several transition metals form complexes with O2, and many of these complexes form reversibly. The binding of O2 is the first step in many important phenomena, such as cellular respiration, corrosion, and industrial chemistry. The first synthetic oxygen complex was demonstrated in 1938 with cobalt(II) complex reversibly bound O2.
High-valent iron commonly denotes compounds and intermediates in which iron is found in a formal oxidation state > 3 that show a number of bonds > 6 with a coordination number ≤ 6. The term is rather uncommon for hepta-coordinate compounds of iron. It has to be distinguished from the terms hypervalent and hypercoordinate, as high-valent iron compounds neither necessarily violate the 18-electron rule nor necessarily show coordination numbers > 6. The ferrate(VI) ion [FeO4]2− was the first structure in this class synthesized. The synthetic compounds discussed below contain highly oxidized iron in general, as the concepts are closely related.
Binding selectivity is defined with respect to the binding of ligands to a substrate forming a complex. Binding selectivity describes how a ligand may bind more preferentially to one receptor than another. A selectivity coefficient is the equilibrium constant for the reaction of displacement by one ligand of another ligand in a complex with the substrate. Binding selectivity is of major importance in biochemistry and in chemical separation processes.
Cyclam (1,4,8,11-tetraazacyclotetradecane) is an organic compound with the formula (NHCH2CH2NHCH2CH2CH2)2. It is a white solid that is soluble in water. The compound is notable as a macrocyclic ligand, which binds strongly to many transition metal cations. The compound was first prepared by the reaction of 1,3-dibromopropane and ethylenediamine.
NKG2D is a transmembrane protein belonging to the CD94/NKG2 family of C-type lectin-like receptors. NKG2D is encoded by KLRK1 gene which is located in the NK-gene complex (NKC) situated on chromosome 6 in mice and chromosome 12 in humans. In mice, it is expressed by NK cells, NK1.1+ T cells, γδ T cells, activated CD8+ αβ T cells and activated macrophages. In humans, it is expressed by NK cells, γδ T cells and CD8+ αβ T cells. NKG2D recognizes induced-self proteins from MIC and RAET1/ULBP families which appear on the surface of stressed, malignant transformed, and infected cells.
The Weak-Link Approach (WLA) is a supramolecular coordination-based assembly methodology, first introduced in 1998 by the Mirkin Group at Northwestern University. This method takes advantage of hemilabile ligands, containing both strong and weak binding moieties, that can coordinate to metal centers and quantitatively assemble into a single condensed ‘closed’ structure. Unlike other supramolecular assembly methods, the WLA allows for the synthesis of supramolecular complexes that can be modulated from rigid ‘closed’ structures to flexible ‘open’ structures through reversible binding events that occur at the structural metal centers. The approach is general and has been applied to a variety of metal centers and ligand designs including those with utility in catalysis and allosteric regulation.
2,6-Diacetylpyridine is an organic compound with the formula C5H3N(C(O)CH3)2. It is a white solid that is soluble in organic solvents. It is a disubstituted pyridine. It is a precursor to ligands in coordination chemistry.
A CXCR4 antagonist is a substance which blocks the CXCR4 receptor and prevent its activation. Blocking the receptor stops the receptor's ligand, CXCL12, from binding which prevents downstream effects. CXCR4 antagonists are especially important for hindering cancer progression because one of the downstream effects initiated by CXCR4 receptor activation is cell movement which helps the spread of cancer, known as metastasis. The CXCR4 receptor has been targeted by antagonistic substances since being identified as a co-receptor in HIV and assisting the development of cancer. Macrocyclic ligands have been utilised as CXCR4 antagonists.
In chemistry, a macrocyclic ligand is a macrocycle with a ring size of at least nine and three or more donor sites. Classic examples are crown ethers and porphyrins. Macrocyclic ligands exhibit particularly high affinity for metal ions.
Penelope Jane Brothers is a New Zealand chemistry academic. She is currently Director of the Research School of Chemistry at the Australian National University, specializing in inorganic chemistry.
Sally Anne Brooker is a New Zealand inorganic chemist. She has been a full professor at the University of Otago since 2006.
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