en>Dieppu at 10:26, 12 September 2014

2014-09-12T10:26:11Z

en>Runningonbrains: /* Space VLBI */ "through until" --> "until"

2013-12-13T05:43:00Z

Space VLBI: "through until" --> "until"

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'''Polyphosphates''' are [[Salt (chemistry)|salt]]s or [[ester]]s of polymeric [[oxyanion]]s formed from [[tetrahedral]] PO4 ([[phosphate]]) structural units linked together by sharing oxygen atoms. Polyphosphates can adopt linear or a cyclic ring structures. In biology the polyphosphate esters [[adenosine monophosphate|AMP]], [[adenosine diphosphate|ADP]] and [[adenosine triphosphate|ATP]] are involved in energy storage. A variety of polyphosphates find application in mineral sequestration in municipal waters, generally being present at 1 to 5 pm.<ref>http://www.jacksmagic.com/pdfs/FAQ_phosphates.pdf</ref> [[guanosine triphosphate|GTP]], [[cytidine triphosphate|CTP]], and [[uridine triphosphate|UTP]] are also nucleotides important in the protein synthesis, lipid synthesis, and carbohydrate metabolism, respectively.



== Structure==
<gallery widths="180px">
Image:Triphosphorsäure.svg|Structure of [[triphosphoric acid]]
Image:Polyphosphoric acid.svg|[[Polyphosphoric acid]]
Image:Trimetaphosphat.svg|Cyclic trimetaphosphate
Image:Adenosindiphosphat protoniert.svg|[[Adenosine diphosphate]] (ADP)
</gallery>
The structure of tripolyphosphoric acid illustrates the principles which define the structures of polyphosphates. It consists of three tetrahedral PO4 units linked together by sharing oxygen centres. For the linear chains, the end phosphorus groups share one oxide and the others phosphorus centres share two oxide centres. The corresponding phosphates are related to the acids by loss of the [[acidic]] protons. In the case of the cyclic trimer each tetrahedron shares two vertices with adjacent tetrahedra.

Sharing of three corners is possible. This motif represents [[crosslinking]] of the linear polymer. Crosslinked polyphosphates adopt the sheet-structure [[Silicate minerals|Phyllosilicates]], but such structures occur only under extreme conditions.

==Formation and synthesis==
Polyphosphates arise by polymerization of phosphoric acid derivatives. The process begins with two phosphate units coming together in what is called a condensation reactoin.
:2 HPO42− {{eqm}} P2O74− + H2O
The condensation is shown as an [[chemical equilibrium|equilibrium]] because the reverse reaction, [[hydrolysis]], is also possible. The process may continue in steps; at each step another PO3 unit is added to the chain, as indicated by the part in brackets in the illustration of polyphosphoric acid. P4O10 can be seen as the end product of condensation reactions, where each tetrahedron shares three corners with the others. Conversely, a complex mix of polymers is produced when a small amount of water is added to phosphorus pentoxide.

== Acid-base and complexation properties ==
Polyphosphates are [[Base (chemistry)|weak base]]s. A lone pair of electrons on an oxygen atom can be donated to a [[hydrogen ion]] (proton) or a metal ion in a typical [[Lewis acid]]-[[Lewis base]] interaction. This has profound significance in biology. For instance, adenosine triphosphate is about 25% protonated in aqueous solution at pH 7.<ref name=Storer>{{cite journal | author = Storer A, Cornish-Bowden A | title = Concentration of MgATP2- and other ions in solution. Calculation of the true concentrations of species present in mixtures of associating ions | pmc=1164030 | journal = Biochem J | volume = 159 | issue = 1 | pages = 1–5 | year = 1976 | pmid = 11772}}</ref>
:ATP4- + H+ {{eqm}} ATPH3-, pKa <math>\approx</math> 6.6
Further protonation occurs at lower pH values.

== The "high energy" phosphate bond ==
ATP forms [[chelation|chelate]] complexes with metal ions. The [[stability constants of complexes|stability constant]] for the equilibrium
:ATP4- + Mg2+ {{eqm}} MgATP2-, log β <math>\approx</math> 4
is particularly large.<ref>{{cite journal | author = Wilson J, Chin A | title = Chelation of divalent cations by ATP, studied by titration calorimetry | journal = Anal Biochem | volume = 193 | issue = 1 | pages = 16–9 | year = 1991 | pmid = 1645933| doi=10.1016/0003-2697(91)90036-S}}</ref> The formation of the magnesium complex is a critical element in the process of ATP hydrolysis, as it weakens the link between the terminal phosphate group and the rest of the molecule.<ref name=Storer/><ref>{{cite journal | author = Garfinkel L, Altschuld R, Garfinkel D | title = Magnesium in cardiac energy metabolism | journal = J Mol Cell Cardiol | volume = 18 | issue = 10 | pages = 1003–13 | year = 1986 | pmid = 3537318 | doi = 10.1016/S0022-2828(86)80289-9 }}</ref>

The energy released in ATP hydrolysis,
:ATP4- + H2O → ADP3- + Pi-
at ΔG <math>\approx</math> -36.8 kJ mol−1 is large by biological standards. Pi stands for inorganic phosphate, which is protonated at biological pH. However, it is not large by inorganic standards. The term "high energy" refers to the fact that it is high relative to the amount of energy released in the [[organic chemistry|organic chemical]] reactions that can occur in living systems.

==High-polymeric inorganic polyphosphates==
High molecular weight polyphosphates are well known.<ref>{{Greenwood&Earnshaw2nd}}</ref> One derivative is the [[glass]]y (i.e., amorphous) Graham’s salt. Crystalline high molecular weight polyphosphates include Kurrol’s salt and Maddrell’s salt. These species have the formula [NaPO3]n[NaPO3(OH)]2 where n can be as great as 2000. In terms of their structures, these polymers consist of PO3- "monomers", with the chains are terminated by protonated phosphates.<ref name=Ullmann>Klaus Schrödter, Gerhard Bettermann, Thomas Staffel, Friedrich Wahl, Thomas Klein, Thomas Hofmann "Phosphoric Acid and Phosphates" in ''Ullmann’s Encyclopedia of Industrial Chemistry'' 2008, Wiley-VCH, Weinheim. {{DOI|10.1002/14356007.a19_465.pub3}}</ref>

===In nature===
High-polymeric inorganic polyphosphates were found in living organisms by L. Liberman in 1890. These compounds are linear polymers containing a few to several hundred residues of [[Phosphoric acids and Phosphates#Orthophosphate|orthophosphate]] linked by energy-rich [[phosphoanhydride]] bonds.

Previously, it was considered either as “molecular fossil” or as only a phosphorus and energy source providing the survival of microorganisms under extreme conditions. These compounds are now known to also have regulatory roles, and to occur in representatives of all kingdoms of living organisms, participating in metabolic correction and control on both genetic and enzymatic levels. Polyphosphate is directly involved in the switching-over of the genetic program characteristic of the exponential growth stage of bacteria to the program of cell survival under stationary conditions, “a life in the slow line”. They participate in many regulatory mechanisms occurring in bacteria:
*They participate in the induction of rpoS, an RNA-polymerase subunit which is responsible for the expression of a large group of genes involved in adjustments to the stationary growth phase and many stressful agents.
*They are important for cell motility, biofilms formation and virulence.
*Polyphosphates and [[exopolyphosphatase]]s participate in the regulation of the levels of the stringent response factor, guanosine 5'-diphosphate 3'-diphosphate (ppGpp), a second messenger in bacterial cells.
*Polyphosphates participate in the formation of channels across the living cell membranes. The above channels formed by polyphosphate and poly-b-hydroxybutyrate with Ca2+ are involved in the transport processes in a variety of organisms.
*An important function of polyphosphate in microorganisms—prokaryotes and the lower eukaryotes—is to handle changing environmental conditions by providing phosphate and energy reserves. Polyphosphates are present in animal cells, and there are many data on its participation in the regulatory processes during development and cellular proliferation and differentiation—especially in bone tissues and brain.

In humans polyphosphates are shown to play a key role in blood [[coagulation]]. Produced and released by [[platelet]]s<ref name="pmid15308650">{{cite journal | author = Ruiz FA, Lea CR, Oldfield E, Docampo R | title = Human platelet dense granules contain polyphosphate and are similar to acidocalcisomes of bacteria and unicellular eukaryotes | journal = J Biol Chem | volume = 279 | issue = 43 | pages = 44250–7 |date=Oct 2004 | pmid = 15308650 | doi = 10.1074/jbc.M406261200 | url = }}</ref>they activate [[Factor XII]] which is essential for blood clot formation. Furthermore platelets-derived polyphosphates activate blood coagulation factor XII (Hageman factor) that initiates fibrin formation and the generation of a proinflammatory mediator, bradykinin that contributes to [[Inflammation#Exudative_component|leakage]] from the blood vessels and thrombosis.<ref name="pmid20005807">{{cite journal | author = Müller F, Mutch, NJ, Schenk WA, Smith SA, Esterl L, Spronk HM, Schmidbauer S, Gahl WA, Morrissey JH, Renné T | title = Platelet polyphosphates are proinflammatory and procoagulant mediators in vivo | journal = CELL | volume = 139 | issue = 6 | pages = 1143–56 |date=Dec 2009 | pmid = 20005807 | pmc = 2796262 | doi = 10.1016/j.cell.2009.11.001| url = }}</ref><ref>{{cite web |url=http://www.physorg.com/news179673245.html |title=Newly discovered mechanism by which blood clots form |work=physorg.com |date=December 10, 2009|accessdate=13 December 2009}}</ref>
Inorganic polyphosphates play a crucial role in tolerance of yeast cells to toxic heavy metal cations. <ref name="pmid23663411">{{cite journal | author = Andreeva N, Ryazanova L, Dmitriev V, Kulakovskaya T, Kulaev I. | title = Adaptation of Saccharomyces cerevisiae to toxic manganese concentration triggers changes in inorganic polyphosphates.| journal = FEMS Yeast Res | volume = 13 | issue = 5 | pages = 463–470 |date=Aug 2013| pmid = 236634411 | doi = 10.1111/1567-1364.12049| url = }}</ref>

== See also ==
*[[Phosphoric acids]]
*[[Sodium trimetaphosphate]]
*[[Sodium hexametaphosphate]]

==References==
{{reflist}}

==External links==
*{{cite journal |author=Pavlov E, Grimbly C, Diao CT, French RJ |title=A high-conductance mode of a poly-3-hydroxybutyrate/calcium/polyphosphate channel isolated from competent Escherichia coli cells |journal=FEBS Lett. |volume=579 |issue=23 |pages=5187–92 |date=September 2005 |pmid=16150446 |doi=10.1016/j.febslet.2005.08.032 |url=http://linkinghub.elsevier.com/retrieve/pii/S0014-5793(05)01027-6}}
*{{cite journal |doi=10.1016/S1389-1723(99)80189-3 |author=Kulaev I, Vagabov V, Kulakovskaya T |title=New aspects of inorganic polyphosphate metabolism and function |journal=J. Biosci. Bioeng. |volume=88 |issue=2 |pages=111–29 |year=1999 |pmid=16232585 |url=http://linkinghub.elsevier.com/retrieve/pii/S1389-1723(99)80189-3}}
*{{cite journal |author=Kulaev I, Kulakovskaya T |title=Polyphosphate and phosphate pump |journal=Annu. Rev. Microbiol. |volume=54 |issue= |pages=709–34 |year=2000 |pmid=11018142 |doi=10.1146/annurev.micro.54.1.709 |url=http://arjournals.annualreviews.org/doi/abs/10.1146/annurev.micro.54.1.709}}
*{{cite journal |author=Kulakovskaya T |title=Inorganic Polyphosphates: Jack of All Trades |journal=Biochem Physiol |volume=1 |issue=2 | |year=2012 |url=
http://www.omicsgroup.org/journals/2168-9652/2168-9652-1-e107.pdf}}

[[Category:Phosphates]]
[[Category:Polymers]]

Very-long-baseline interferometry - Revision history

en>Dieppu at 10:26, 12 September 2014

en>Runningonbrains: /* Space VLBI */ "through until" --> "until"