Chelation (from Greek χηλή, chelè, meaning claw; pronounced /kiːˈleɪʃən/) is the binding or complexation of a bi- or multidentate ligand. Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly Molecular binding is an attractive interaction between two Molecules which results in a stable association in which the two molecules are in close proximity to each other The term complex in Chemistry is usually used to describe molecules or ensembles formed by the combination of Ligands and metal Ions. In Chemistry, a ligand is either an Atom, Ion, or Molecule (see also Functional group) that bonds to a central metal generally These ligands, which are often organic compounds, are called chelants, chelators, chelating agents, or sequestering agent. An organic compound is any member of a large class of Chemical compounds whose Molecules contain Carbon. The term sequestration can have different meanings according to the context The ligand forms a chelate complex with the substrate. The term is reserved for complexes in which the metal ion is bound to two or more atoms of the chelating agent, although the bonds may be any combination of covalent, coordinate covalent, or ionic bonds. A coordinate covalent bond (formerly also known as dative bond) is a description of Covalent bonding between two atoms in which both electrons shared in the bond come An ionic bond (or electrovalent bond) is a type of Chemical bond that can often form between Metal and Non-metal Ions (or

Metal-EDTA chelate. EDTA is a widely used abbreviation for the Chemical compound ethylenediaminetetraacetic acid (and many other names see table

History

The term chelate was first applied in 1920 by Sir Gilbert T. Year 1920 ( MCMXX) was a Leap year starting on Thursday (link will display 1920 of the Gregorian calendar Morgan and H. D. K. Drew, who stated: "The adjective chelate, derived from the great claw or chele (Greek) of the lobster or other crustaceans, is suggested for the caliperlike groups which function as two associating units and fasten to the central atom so as to produce heterocyclic rings. Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly Clawed lobsters compose a family ( Nephropidae, sometimes also Homaridae) of large marine Crustaceans Lobsters are economically important as "^[1]

General

Relative to the aqua complexes, e. The term complex in Chemistry is usually used to describe molecules or ensembles formed by the combination of Ligands and metal Ions. g. [M(H₂O)₆]²⁺, the increased stability of a chelated complex, e. g. [M(EDTA]^2- is called the chelate effect. EDTA is a widely used abbreviation for the Chemical compound ethylenediaminetetraacetic acid (and many other names see table Because chelating agents bind to metals through more than one coordination site, such ligands bind more tenaciously than unidentate ligands (like water). If a chelate were replaced by several monodentate ligands (such as water or ammonia), the total number of molecules would decrease, whereas if several monodentate ligands were replaced by a chelate, the number of free molecules increases. Water is a common Chemical substance that is essential for the survival of all known forms of Life. Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor The effect is therefore entropic in that more sites are used by fewer ligands and this leaves more unbonded molecules: a total increase in the number of molecules in solution and a corresponding increase in entropy. In Thermodynamics (a branch of Physics) entropy, symbolized by S, is a measure of the unavailability of a system ’s Energy

Chelation in nature

Virtually all biochemicals exhibit the ability to dissolve metal cations. Thus proteins, polysaccharides, and polynucleic acids are excellent polydentate ligands for many of the metal ions. In addition to these adventitious chelators, several are produced to specifically bind certain metals. Such chelating agents include the porphyrin rings in hemoglobin or chlorophyll and the Fe³⁺-chelating siderophores secreted by microorganisms. A porphyrin is a heterocyclic Macrocycle derived from four Pyrroline subunits interconnected via their α carbon atoms via Methine bridges (=CH- Hemoglobin ( also spelled haemoglobin and abbreviated Hb or Hgb) is the Iron -containing Oxygen -transport Metalloprotein Chlorophyll is a green Pigment found in most Plants Algae and Cyanobacteria. Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 A Siderophore (Greek for iron carrier is an Iron chelating compound secreted by Microorganisms such as bacteria fungi and grasses A microorganism (also spelled micro organism or micro-organism and also called a microbe) is an Organism that is Microscopic (usually Histidine, malate and phytochelatin are typical chelators used by plants to avoid having poisonous metal ions in a free form. Histidine (abbreviated as His or H) is one of the 20 standard Amino acids present in Proteins In the Nutritional sense in Malic acid is an Organic compound with the formula HO2CCH2CHOHCO2H Phytochelatins are Oligomers of Glutathione, produced by the enzyme phytochelatin synthase ^[2][3][4]

In geology

In earth science, chemical weathering is attributed to organic chelating agents, e. Weathering is the decomposition of earth rocks, Soils and their Minerals through direct contact with the planet's Atmosphere. g. peptides and sugars, that have the ability to solubilize the metal ions in minerals and rocks. Peptides (from the Greek πεπτίδια, "small digestibles" are short Polymers formed from the linking in a defined order of α- Amino Sugar is a class of edible Crystalline substances mainly Sucrose, Lactose, and Fructose. ^[5] Most metal complexes in the environment and in nature are bound in some form of chelate ring, e. g. with "humic acid" or a protein. Humic acid is one of the major components of humic substances which are dark brown and major constituents of soil organic matter Humus that contributes to Soil chemical Thus, metal chelates are relevant to the mobilization of metals in the soil, the uptake and the accumulation of metals into plants and micro-organisms. The M acro E xpansion T emplate A ttribute L anguage complements TAL, providing macros which allow the reuse of code across Soil, often typeset as SOiL, is a four piece rock band from Chicago Illinois United States founded by Shaun Glass Tom Schofield Tim King and Adam Zadel The M acro E xpansion T emplate A ttribute L anguage complements TAL, providing macros which allow the reuse of code across Plants are living Organisms belonging to the kingdom Plantae. A microorganism (also spelled micro organism or micro-organism and also called a microbe) is an Organism that is Microscopic (usually Selective chelation of heavy metals is relevant to bioremediation, e. Bioremediation can be defined as any process that uses Microorganisms Fungi, green plants or their Enzymes to return the natural environment altered g. removal of ¹³⁷Cs from radioactive waste. ^[6]

In microbiology

Many microbial species produce water-soluble pigments that are fluorescent under UV light. These pigments serve as chelating agents, termed siderophores. A Siderophore (Greek for iron carrier is an Iron chelating compound secreted by Microorganisms such as bacteria fungi and grasses Among species of Pseudomonas, they are known to secrete pycocyanin and pyoverdin that bind to Iron.

Uses

Chelators are used in chemical analysis, as water softeners, and are ingredients in many commercial products such as shampoos and food preservatives. Analytical chemistry is the study of the Chemical composition of natural and artificial Materials. A water softener reduces the dissolved Calcium, Magnesium, and to some degree Manganese and Ferrous iron ion concentration in Hard water Shampoo is a Hair care product used for the removal of oils, dirt skin particles Dandruff, environmental pollutants and other contaminant particles that A preservative is a natural or synthetic chemical that is added to products such as foods pharmaceuticals paints biological samples wood etc Citric acid is used to soften water in soaps and laundry detergents. Citric acid is a weak organic Acid. It is a natural Preservative and is also used to add an acidic or sour taste to foods and Soft drinks Citric acid is a weak organic Acid. It is a natural Preservative and is also used to add an acidic or sour taste to foods and Soft drinks SOAP (see below for name and origins is a protocol for exchanging XML -based messages over Computer networks normally using A detergent (as a noun is a material intended to assist Cleaning. A commonly used synthetic chelator is EDTA. EDTA is a widely used abbreviation for the Chemical compound ethylenediaminetetraacetic acid (and many other names see table The term is used in water treatment programs and specifically in steam engineering, to describe a boiler water treatment system: Chelant Water Treatment system.

In medicine

Antibiotic drugs of the tetracycline family are chelators of Ca²⁺ and Mg²⁺ ions. In modern usage an antibiotic is a Chemotherapeutic agent with activity against Microorganisms such as Bacteria, fungi or Protozoa Medication, also referred to as medicine, can be loosely defined as any substance intended for use in the diagnosis cure mitigation treatment or prevention of disease This article deals with the specific antibiotic called tetracycline Calcium (ˈkælsiəm is the Chemical element with the symbol Ca and Atomic number 20 Magnesium (mægˈniːziəm is a Chemical element with the symbol Mg, Atomic number 12 Atomic weight 24 Chelation therapy describes the use of chelating agents to detoxify poisonous metal agents such as mercury, arsenic, and lead by converting them to a chemically inert form that can be excreted without further interaction with the body. Chelation therapy is the administration of chelating agents to remove Heavy metals from the body In the context of Biology, poisons are substances that can cause damage, Illness, or Death to Organisms usually by Mercury poisoning (also known as mercurialism, hydrargyria, Hunter-Russell syndrome, or acrodynia when affecting children is a Disease Arsenic (ˈɑrsənɪk is a Chemical element that has the symbol As and Atomic number of 33 Characteristics Lead has a dull luster and is a dense, Ductile, very soft highly Chelation is also used as an unscientific treatment for autism or other conditions. Many medications are used to treat problems associated with ASD Language development. The terminology There are no peer-reviewed publications regarding the efficacy of chelation agents for the treatment of autism. ^[7]

EDTA chelation can be a dangerous practice, especially when Na₂EDTA is prescribed rather than CaEDTA. The CDC reports that use of Na₂EDTA has resulted in fatalities due to hypocalcemia. In Medicine, hypocalcaemia is the presence of low serum Calcium levels in the Blood, usually taken as less than 2 ^[8]

EDTA is also used in root canal treatment as a way to irrigate the canal. A root canal is the commonly used term for the main canals within the Dentin of the tooth EDTA is used as a chelating agent to soften the dentin facilitating access to the entire canal length and to remove the smear layer formed during instrumentation.

Gadolinium(III) chelates are often used as contrast agents in MRI scans. Gadolinium (ˌgædəˈlɪniəm is a Chemical element that has the symbol Gd and Atomic number 64

See also

• Bioremediation
• Chelation therapy
• Electron counting

References

1. ^ J. Bioremediation can be defined as any process that uses Microorganisms Fungi, green plants or their Enzymes to return the natural environment altered Chelation therapy is the administration of chelating agents to remove Heavy metals from the body Electron counting is a formalism used for classifying compounds and for explaining or predicting electronic structure and bonding. Chem. Soc. , 1920, 117, 1456
2. ^ U Krämer, J D Cotter-Howells, J M Charnock, A H J M Baker, J A C Smith (1996). "Free histidine as a metal chelator in plants that accumulate nickel". Nature 379. doi:10.1038/379635a0. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.  
3. ^ Jurandir Vieira Magalhaes (2006). "Aluminum tolerance genes are conserved between monocots and dicots". Proc Natl Acad Sci U S A 103 (26): 9749. doi:10.1073/pnas.0603957103. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.  
4. ^ Suk-Bong Ha, Aaron P. Smith, Ross Howden, Wendy M. Dietrich, Sarah Bugg, Matthew J. O'Connell, Peter B. Goldsbrough, and Christopher S. Cobbett (1999). "Phytochelatin synthase genes from arabidopsis and the yeast Schizosaccharomyces pombe". Plant Cell 11.  
5. ^ Dr. Michael Pidwirny, University of British Columbia Okanagan, http://www.physicalgeography.net/fundamentals/10r.html
6. ^ Prasad (ed). Metals in the Environment. University of Hyderabad. Dekker, New York, 2001
7. ^ Doja A, Roberts W (2006). "Immunizations and autism: a review of the literature". Can J Neurol Sci 33 (4): 341–46. PMID 17168158.  
8. ^ U. S. Centers for Disease Control, "Deaths Associated with Hypocalcemia from Chelation Therapy" (March 3, 2006), http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5508a3.htm