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| {{Infobox protein family
| | It is very common to have a dental emergency -- a fractured tooth, an abscess, or severe pain when chewing. Over-the-counter pain medication is just masking the problem. Seeing an emergency dentist is critical to getting the source of the problem diagnosed and corrected as soon as possible.<br><br>Here are some common dental emergencies:<br>Toothache: The most common dental emergency. This generally means a badly decayed tooth. As the pain affects the tooth's nerve, treatment involves gently removing any debris lodged in the cavity being careful not to poke deep as this will cause severe pain if the nerve is touched. Next rinse vigorously with warm water. Then soak a small piece of cotton in oil of cloves and insert it in the cavity. This will give temporary relief until a dentist can be reached.<br><br>At times the pain may have a more obscure location such as decay under an old filling. As this can be only corrected by a dentist there are two things you can do to help the pain. Administer a pain pill (aspirin or some other analgesic) internally or dissolve a tablet in a half glass (4 oz) of warm water holding it in the mouth for several minutes before spitting it out. DO NOT PLACE A WHOLE TABLET OR ANY PART OF IT IN THE TOOTH OR AGAINST THE SOFT GUM TISSUE AS IT WILL RESULT IN A NASTY BURN.<br><br>Swollen Jaw: This may be caused by several conditions the most probable being an abscessed tooth. In any case the treatment should be to reduce pain and swelling. An ice pack held on the outside of the jaw, (ten minutes on and ten minutes off) will take care of both. If this does not control the pain, an analgesic tablet can be given every four hours.<br><br>Other Oral Injuries: Broken teeth, cut lips, bitten tongue or lips if severe means a trip to a dentist as soon as possible. In the mean time rinse the mouth with warm water and place cold compression the face opposite the injury. If there is a lot of bleeding, apply direct pressure to the bleeding area. If bleeding does not stop get patient to the emergency room of a hospital as stitches may be necessary.<br><br>Prolonged Bleeding Following Extraction: Place a gauze pad or better still a moistened tea bag over the socket and have the patient bite down gently on it for 30 to 45 minutes. The tannic acid in the tea seeps into the tissues and often helps stop the bleeding. If bleeding continues after two hours, call the dentist or take patient to the emergency room of the nearest hospital.<br><br>Broken Jaw: If you suspect the patient's jaw is broken, bring the upper and lower teeth together. Put a necktie, handkerchief or towel under the chin, tying it over the head to immobilize the jaw until you can get the patient to a dentist or the emergency room of a hospital.<br><br>Painful Erupting Tooth: In young children teething pain can come from a loose baby tooth or from an erupting permanent tooth. Some relief can be given by crushing a little ice and wrapping it in gauze or a clean piece of cloth and putting it directly on the tooth or gum tissue where it hurts. The numbing effect of the cold, along with an appropriate dose of aspirin, usually provides temporary relief.<br><br>In young adults, an erupting 3rd molar (Wisdom tooth), especially if it is impacted, can cause the jaw to swell and be quite painful. Often the gum around the tooth will show signs of infection. Temporary relief can be had by giving aspirin or some other painkiller and by dissolving an aspirin in half a glass of warm water and holding this solution in the mouth over the sore gum. AGAIN DO NOT PLACE A TABLET DIRECTLY OVER THE GUM OR CHEEK OR USE THE ASPIRIN SOLUTION ANY STRONGER THAN RECOMMENDED TO PREVENT BURNING THE TISSUE. The swelling of the jaw can be reduced by using an ice pack on the outside of the face at intervals of ten minutes on and ten minutes off.<br><br>If you have any kind of questions regarding where and how you can utilize [http://www.youtube.com/watch?v=90z1mmiwNS8 Best Dentists in DC], you could call us at our web page. |
| | Symbol = AFP
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| | Name = Insect antifreeze protein repeat
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| | image = PDB 1l1i EBI.jpg
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| | width =
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| | caption = Structure of the ''[[Tenebrio molitor]]'' beta-helical antifreeze protein<ref name="pmid11969412">{{cite journal | author = Daley ME, Spyracopoulos L, Jia Z, Davies PL, Sykes BD | title = Structure and dynamics of a beta-helical antifreeze protein | journal = Biochemistry | volume = 41 | issue = 17 | pages = 5515–25 |date=April 2002 | pmid = 11969412 | doi = 10.1021/bi0121252 }}</ref>
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| | Pfam = PF02420
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| | Pfam_clan =
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| | InterPro = IPR003460
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| | SMART =
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| | PROSITE =
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| | MEROPS =
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| | SCOP = 1ezg
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| | TCDB =
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| | OPM family =
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| | OPM protein =
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| | PDB =
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| }}
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| {{Infobox protein family
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| | Symbol = CfAFP
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| | Name = ''Choristoneura fumiferana'' antifreeze protein (CfAFP)
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| | image = PDB 1m8n EBI.jpg
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| | width =
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| | caption = Structure of ''Choristoneura fumiferana'' (spruce budworm) beta-helical antifreeze protein<ref name="pmid12105229">{{cite journal | author = Leinala EK, Davies PL, Doucet D, Tyshenko MG, Walker VK, Jia Z | title = A beta-helical antifreeze protein isoform with increased activity. Structural and functional insights | journal = J. Biol. Chem. | volume = 277 | issue = 36 | pages = 33349–52 |date=September 2002 | pmid = 12105229 | doi = 10.1074/jbc.M205575200 }}</ref>
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| | Pfam = PF05264
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| | Pfam_clan =
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| | InterPro = IPR007928
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| | SMART =
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| | PROSITE =
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| | MEROPS =
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| | SCOP = 1m8n
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| | TCDB =
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| | OPM family = 392
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| | OPM protein = 1l0s
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| | PDB =
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| }}
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| '''Antifreeze proteins (AFPs)''' or '''ice structuring proteins (ISPs)''' refer to a class of [[polypeptides]] produced by certain [[vertebrate]]s, [[plant]]s, [[fungi]] and [[bacteria]] that permit their survival in subzero environments. AFPs bind to small [[ice crystals]] to inhibit growth and [[crystallization|recrystallization]] of ice that would otherwise be fatal.<ref name="Madura2001">http://www.rcsb.org/pdb/101/motm.do?momID=120</ref> There is also increasing evidence that AFPs interact with mammalian cell membranes to protect them from cold damage. This work suggests the involvement of AFPs in cold [[acclimatization]].<ref name="Fletcher2001">{{cite journal | author = Fletcher GL, Hew CL, Davies PL | title = Antifreeze proteins of teleost fishes | journal = Annu. Rev. Physiol. | volume = 63 | issue = | pages = 359–90 | year = 2001 | pmid = 11181960 | doi = 10.1146/annurev.physiol.63.1.359 }}</ref>
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| ==Non-colligative properties==
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| Unlike the widely used automotive antifreeze, [[ethylene glycol]], AFPs do not lower freezing point in proportion to concentration. Rather, they work in a non[[colligative]] manner. This phenomenon allows them to act as an antifreeze at concentrations 1/300th to 1/500th of those of other dissolved solutes. Their low concentration minimizes their effect on [[osmotic pressure]].<ref name="Fletcher2001" /> The unusual properties of AFPs are attributed to their affinity for specific ice crystal surfaces.<ref name="Jorov2004">{{cite journal | author = Jorov A, Zhorov BS, Yang DS | title = Theoretical study of interaction of winter flounder antifreeze protein with ice | journal = Protein Sci. | volume = 13 | issue = 6 | pages = 1524–37 |date=June 2004 | pmid = 15152087 | pmc = 2279984 | doi = 10.1110/ps.04641104 }}</ref>
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| ==Thermal hysteresis==
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| AFPs create a difference between the melting point and freezing point known as thermal hysteresis. The addition of AFPs at the interface between solid ice and liquid water inhibits the thermodynamically favored growth of the ice crystal. Ice growth is kinetically inhibited by the AFPs covering the water-accessible surfaces of ice.<ref name="Jorov2004" />
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| Thermal hysteresis is easily measured in the lab with a [[nanolitre osmometer]]. Organisms differ in their values of thermal hysteresis. The maximum level of thermal hysteresis shown by fish AFP is approximately -1.5°C (29.3°F). However, insect antifreeze proteins are 10–30 times more active than fish proteins. This difference probably reflects the lower temperatures encountered by insects on land. In contrast, aquatic organisms are exposed only to –1 to –2°C below freezing. During the extreme winter months, the [[spruce budworm]] resist freezing at temperatures approaching –30 °C.<ref name="Fletcher2001" /> The Alaskan beetle [[Xylomannan|''Upis ceramboides'']] can survive in a temperature of –60 °C by using antifreeze agents that are not proteins.<ref name="Walters KR Jr, Serianni AS, Sformo T, Barnes BM, Duman JG 2009 20210–5">{{cite journal | author=Walters KR Jr, Serianni AS, Sformo T, Barnes BM, Duman JG | title=A nonprotein thermal hysteresis-producing xylomannan antifreeze in the freeze-tolerant Alaskan beetle Upis ceramboides | journal=[[Proceedings of the National Academy of Sciences|PNAS]] | volume= 106 | issue= 48| year=2009 | pages= 20210–5| pmid=19934038 | pmc=2787118 | doi=10.1073/pnas.0909872106 }}</ref>
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| The rate of cooling can influence the thermal hysteresis value of AFPs. Rapid cooling can substantially decrease the nonequilibrium freezing point, and hence the thermal hysteresis value. Consequently, organisms cannot necessarily adapt to their subzero environment if the temperature drops abruptly.<ref name="Fletcher2001" />
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| ==Freeze tolerance versus freeze avoidance==
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| Species containing AFPs may be classified as
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| '''Freeze avoidant''': These species are able to prevent their body fluids from freezing altogether. Generally, the AFP function may be overcome at extremely cold temperatures, leading to rapid ice growth and death.
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| '''Freeze tolerant''': These species are able to survive body fluid freezing. Some freeze tolerant species are thought to use AFPs as cryoprotectants to prevent the damage of freezing, but not freezing altogether. The exact mechanism is still unknown. However, it is thought AFPs may inhibit recrystallization and stabilize cell membranes to prevent damage by ice.<ref name="Duman2001">{{cite journal | author = Duman JG | title = Antifreeze and ice nucleator proteins in terrestrial arthropods | journal = Annu. Rev. Physiol. | volume = 63 | issue = | pages = 327–57 | year = 2001 | pmid = 11181959 | doi = 10.1146/annurev.physiol.63.1.327 | url = }}</ref> They may work in conjunction with [[protein ice nucleator]]s (PINs) to control the rate of ice propagation following freezing.<ref name="Duman2001" />
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| == Diversity ==
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| There are many known nonhomologous types of AFPs.
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| ===Fish AFPs===
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| [[Image:AFPnew.svg|frame|'''Figure 1'''. The three faces of Type I AFP]]Antifreeze [[glycoproteins]] or AFGPs are found in [[Antarctica|Antarctic]] notothenioids and northern cod. They are 2.6-3.3 kD.<ref name="Crevel2002">{{cite journal | author = Crevel RW, Fedyk JK, Spurgeon MJ | title = Antifreeze proteins: characteristics, occurrence and human exposure | journal = Food Chem. Toxicol. | volume = 40 | issue = 7 | pages = 899–903 |date=July 2002 | pmid = 12065210 | doi =10.1016/S0278-6915(02)00042-X }}</ref> AFGPs evolved separately in notothenioids and northern cod. In notothenioids, the AFGP gene arose from an ancestral trypsinogen-like serine protease gene.<ref name="Chen et. al.1997">{{cite journal | author = Chen, et. al. | title = Evolution of antifreeze glycoprotein gene from a trypsinogen gene in Antarctic notothenioid fish | journal = PNAS | volume = 94 | issue = 8 | pages = 3811–3816 | year = 1997 }}</ref>
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| Type I AFP is found in [[winter flounder]], longhorn sculpin and shorthorn [[sculpin]]. It is the best documented AFP because it was the first to have its three dimensional structure determined.<ref name="Duman and DeVries1976">{{cite journal | author = Duman JG, de Vries AL | title = Isolation, characterization, and physical properties of protein antifreezes from the winter flounder, Pseudopleuronectes americanus | journal = Comp. Biochem. Physiol., B | volume = 54 | issue = 3 | pages = 375–80 | year = 1976 | pmid = 1277804 | doi = }}</ref> Type I AFP consists of a single, long, amphipathic alpha helix, about 3.3-4.5 kD in size. There are three faces to the 3D structure: the hydrophobic, hydrophilic, and Thr-Asx face.<ref name="Duman and DeVries1976" />
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| Type I-hyp AFP (where hyp stands for hyperactive) are found in several righteye flounders. It is approximately 32 kD (two 17 kD dimeric molecules). The protein was isolated from the blood plasma of winter flounder. It is considerably better at depressing freezing temperature than most fish AFPs.<ref name="Scotter2006">{{cite journal | author = Scotter AJ, Marshall CB, Graham LA, Gilbert JA, Garnham CP, Davies PL | title = The basis for hyperactivity of antifreeze proteins | journal = Cryobiology | volume = 53 | issue = 2 | pages = 229–39 |date=October 2006 | pmid = 16887111 | doi = 10.1016/j.cryobiol.2006.06.006 | url = }}</ref>
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| Type II AFPs are found in [[sea raven]], [[Smelt (fish)|smelt]] and [[herring]]. They are cysteine-rich globular proteins containing five [[disulfide bond]]s.<ref name="Ng and Hew1992">{{cite journal | author = Ng NF, Hew CL | title = Structure of an antifreeze polypeptide from the sea raven. Disulfide bonds and similarity to [[lectin]]-binding proteins | journal = J. Biol. Chem. | volume = 267 | issue = 23 | pages = 16069–75 |date=August 1992 | pmid = 1644794 | doi = }}</ref> Type II AFPs likely evolved from calcium dependent (c-type) lectins.<ref name="Ewart et. al.1992">{{cite journal | author = Ewart, et. al. | title = Structural and functional similarity between fish antifreeze proteins and calcium-dependent lectins | journal = Biochem Biophys Res Commun | volume = 185 | pages = 335–340 | year = 1992 }}</ref> Sea ravens, smelt, and herring are quite divergent lineages of teleost. If the AFP gene was present in the most recent common ancestor of these lineages, it's peculiar that the gene is scattered throughout those lineages, present in some orders and absent in others. It has been suggested that lateral gene transfer could be attributed to this discrepancy, such that the smelt acquired the type II AFP gene from the herring.<ref name="Graham et. al.2008">{{cite journal | author = Graham, et. al. | title = Lateral transfer of a lectin-like antifreeze protein gene in fishes | journal = PloS One | volume = 3 | pages = e2616 | year = 2008 }}</ref>
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| Type III AFPs are found in Antarctic [[eelpout]]. They exhibit similar overall hydrophobicity at ice binding surfaces to type I AFPs. They are approximately 6kD in size.<ref name="Crevel2002" /> Type III AFPs likely evolved from a sialic acid synthase gene present in Antarctic zoarcid fish. Through a gene duplication event, this gene—which has been shown to exhibit some ice-binding activity of its own—evolved into an effective AFP gene.<ref name="Kelley et. al.2010">{{cite journal | author = Kelley, et. al. | title = Functional diversification and evolution of antifreeze proteins in the Antarctic fish Lycodichthys dearborni | journal = Journal of Molecular Evolution | volume = 71 | pages = 111–118 | year = 2010 }}</ref>
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| Type IV AFPs are found in longhorn sculpins. They are alpha helical proteins rich in glutamate and glutamine.<ref name="Deng1997">{{cite journal | author = Deng G, Andrews DW, Laursen RA | title = Amino acid sequence of a new type of antifreeze protein, from the longhorn sculpin Myoxocephalus octodecimspinosis | journal = FEBS Lett. | volume = 402 | issue = 1 | pages = 17–20 |date=January 1997 | pmid = 9013849 | doi = 10.1016/S0014-5793(96)01466-4}}</ref> This protein is approximately 12KDa in size and consists of a 4-helix bundle.<ref name="Deng1997" /> Its only posttranslational modification is a [[pyroglutamate]] residue, a cyclized [[glutamine]] residue at its N-terminus.<ref name="Deng1997" /> Scientists at the University of Guelph in Canada are currently examining the role of this pyroglutame residue in the antifreeze activity of type IV AFP from the longhorn sculpin.
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| ===Plant AFPs===
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| The classification of AFPs became more complicated when antifreeze proteins from plants were discovered.<ref name="Griffith1992">{{cite journal | author = Griffith M, Ala P, Yang DS, Hon WC, Moffatt BA | title = Antifreeze protein produced endogenously in winter rye leaves | journal = Plant Physiol. | volume = 100 | issue = 2 | pages = 593–6 |date=October 1992 | pmid = 16653033 | pmc = 1075599 | doi = 10.1104/pp.100.2.593| url = }}</ref> Plant AFPs are rather different from the other AFPs in the following aspects:
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| #They have much weaker thermal hysteresis activity when compared to other AFPs.<ref name="Griffith and Yaish2004">{{cite journal | author = Griffith M, Yaish MW | title = Antifreeze proteins in overwintering plants: a tale of two activities | journal = Trends Plant Sci. | volume = 9 | issue = 8 | pages = 399–405 |date=August 2004 | pmid = 15358271 | doi = 10.1016/j.tplants.2004.06.007 }}</ref>
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| #Their physiological function is likely in inhibiting the recrystallization of ice rather than in the preventing ice formation.<ref name="Griffith and Yaish2004" />
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| #Most of them are evolved [[pathogenesis]]-related proteins, sometimes retaining [[Fungicide|antifungal]] properties.<ref name="Griffith and Yaish2004" />
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| ''See also [[dehydrin]]''
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| ===Insect AFPs===
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| There are two types of insect antifreeze proteins, ''Tenebrio'' and ''Dendroides'' AFPs which are both in different insect families. They are similar to one another, both being hyperactive (i.e. greater thermal hysteresis value) and consist of varying numbers of 12- or 13-mer repeats of approximately 8.3 to 12.5 kD. Throughout the length of the protein, at least every sixth residue is a [[cysteine]].<ref name="Duman2001" />
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| ''Tenebrio'' or Type V AFPs are found in beetles,<ref name="Graham1997">{{cite journal | author = Graham LA, Liou YC, Walker VK, Davies PL | title = Hyperactive antifreeze protein from beetles | journal = Nature | volume = 388 | issue = 6644 | pages = 727–8 |date=August 1997 | pmid = 9285581 | doi = 10.1038/41908 }}</ref> whereas ''Dendroides'' or ''[[Choristoneura fumiferana]]'' AFPs are found in some [[Lepidoptera]].
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| ===Sea ice organisms AFPs===
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| AFPs were also found in microorganisms living in [[sea ice]]. The [[diatom]]s ''Fragilariopsis cylindrus'' and ''F. curta'' play a key role in polar sea ice communities, dominating the assemblages of both platelet layer and within pack ice. AFPs are widespread in these species, and the presence of AFP [[genes]] as a multigene family indicates the importance of this group for the genus ''Fragilariopsis''.<ref name="pmid20105220">{{cite journal | author = Bayer-Giraldi M, Uhlig C, John U, Mock T, Valentin K | title = Antifreeze proteins in polar sea ice diatoms: diversity and gene expression in the genus Fragilariopsis | journal = Environ. Microbiol. | volume = 12 | issue = 4 | pages = 1041–52 |date=April 2010 | pmid = 20105220 | doi = 10.1111/j.1462-2920.2009.02149.x }}</ref> AFPs identified in ''F. cylindrus'' belong to an AFP family which is represented in different taxa and can be found in other organisms related to sea ice (''[[Colwellia]]'' spp., ''[[Navicula glaciei]]'', ''[[Chaetoceros neogracile]]'' and ''[[Stephos longipes]] and Leucosporidium antarcticum''<ref name="pmid17651136">{{cite journal | author = Raymond JA, Fritsen C, Shen K | title = An ice-binding protein from an Antarctic sea ice bacterium | journal = FEMS Microbiol. Ecol. | volume = 61 | issue = 2 | pages = 214–21 |date=August 2007 | pmid = 17651136 | doi = 10.1111/j.1574-6941.2007.00345.x }}</ref><ref>Kiko, R. (2010): Acquisition of freeze protection in a sea-ice crustacean through horizontal gene transfer? Polar Biology (33) 543-556.</ref>) and Antarctic inland ice bacteria ([[Flavobacteriaceae]]),<ref name="pmid18622572">{{cite journal | author = Raymond JA, Christner BC, Schuster SC | title = A bacterial ice-binding protein from the Vostok ice core | journal = Extremophiles | volume = 12 | issue = 5 | pages = 713–7 |date=September 2008 | pmid = 18622572 | doi = 10.1007/s00792-008-0178-2 }}</ref><ref>http://pnwfungi.org/pdf_files/manuscripts_volume_5/naf20105/naf2010514.pdf</ref> as well as in cold-tolerant fungi (''[[Typhula ishikariensis]]'', ''[[Lentinula edodes]]'' and ''[[Flammulina populicola]]''.<ref>Hoshino, T., Kiriaki, M., Ohgiya, S., Fujiwara, M., Kondo, H., Nishimiya, Y., et al. (2003) Antifreeze proteins from [[snow mold]] fungi. Can J Bot 81: 1175–1181.</ref><ref name="pmid19121299">{{cite journal | author = Raymond JA, Janech MG | title = Ice-binding proteins from enoki and shiitake mushrooms | journal = Cryobiology | volume = 58 | issue = 2 | pages = 151–6 |date=April 2009 | pmid = 19121299 | doi = 10.1016/j.cryobiol.2008.11.009 }}</ref>)
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| == Evolution ==
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| The remarkable diversity and distribution of AFPs suggest the different types evolved recently in response to sea level [[glaciation]] occurring 1-2 million years ago in the Northern hemisphere and 10-30 million years ago in Antarctica. This independent development of similar adaptations is referred to as [[convergent evolution]].<ref name="Fletcher2001" /> There are two reasons why many types of AFPs are able to carry out the same function despite their diversity:
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| # Although ice is uniformly composed of [http://www.bell-labs.com/news/1999/january/12/ice1h.jpg oxygen and hydrogen], it has many different surfaces exposed for binding. Different types of AFPs may interact with different surfaces.
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| # Although the five types of AFPs differ in their [[primary sequence]] of amino acids, when each folds into a functioning protein, they may share similarities in their three dimensional or [[tertiary structure]] that facilitates the same interactions with ice.<ref name="Fletcher2001" /><ref name="pmid9108061">{{cite journal | author = Chen L, DeVries AL, Cheng CH | title = Convergent evolution of antifreeze glycoproteins in Antarctic notothenioid fish and Arctic cod | journal = Proc. Natl. Acad. Sci. U.S.A. | volume = 94 | issue = 8 | pages = 3817–22 |date=April 1997 | pmid = 9108061 | pmc = 20524 | doi = 10.1073/pnas.94.8.3817}}</ref>
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| == Mechanisms of action ==
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| AFPs are thought to inhibit growth by an [[adsorption]]–inhibition mechanism.<ref name="Raymond and DeVries1977">{{cite journal | author = Raymond JA, DeVries AL | title = Adsorption inhibition as a mechanism of freezing resistance in polar fishes | journal = Proc. Natl. Acad. Sci. U.S.A. | volume = 74 | issue = 6 | pages = 2589–93 |date=June 1977 | pmid = 267952 | pmc = 432219 | doi = 10.1073/pnas.74.6.2589 }}</ref> They adsorb to non[[basal plane]]s of ice, inhibiting thermodynamically favored ice growth.<ref name="Raymond1989">{{cite journal | author = Raymond JA, Wilson P, DeVries AL | title = Inhibition of growth of non basal planes in ice by fish antifreezes | journal = Proc. Natl. Acad. Sci. U.S.A. | volume = 86 | issue = 3 | pages = 881–5 |date=February 1989 | pmid = 2915983 | pmc = 286582 | doi = 10.1073/pnas.86.3.881 }}</ref> The presence of a flat, rigid surface in some AFPs seems to facilitate its interaction with ice via [[Van der Waals force]] surface complementarity.<ref name="Yang1998">{{cite journal | author = Yang DS, Hon WC, Bubanko S, Xue Y, Seetharaman J, Hew CL, Sicheri F | title = Identification of the ice-binding surface on a type III antifreeze protein with a "flatness function" algorithm | journal = Biophys. J. | volume = 74 | issue = 5 | pages = 2142–51 |date=May 1998 | pmid = 9591641 | pmc = 1299557 | doi = 10.1016/S0006-3495(98)77923-8 }}</ref>
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| == Binding to ice ==
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| Normally, ice crystals grown in solution only exhibit the basal (0001) and prism faces (1010), and appear as round and flat discs.<ref name="Jorov2004" /> However, it appears the presence of AFPs exposes other faces. It now appears the ice surface 2021 is the preferred binding surface, at least for AFP type I.<ref name="Knight1991">{{cite journal | author = Knight CA, Cheng CC, DeVries AL | title = Adsorption of alpha-helical antifreeze peptides on specific ice crystal surface planes | journal = Biophys. J. | volume = 59 | issue = 2 | pages = 409–18 |date=February 1991 | pmid = 2009357 | pmc = 1281157 | doi = 10.1016/S0006-3495(91)82234-2 | url = }}</ref> Through studies on type I AFP, ice and AFP were initially thought to interact through hydrogen bonding (Raymond and DeVries, 1977). However, when parts of the protein thought to facilitate this hydrogen bonding were mutated, the hypothesized decrease in antifreeze activity was not observed. Recent data suggest hydrophobic interactions could be the main contributor.<ref name="pmid9688560">{{cite journal | author = Haymet AD, Ward LG, Harding MM, Knight CA | title = Valine substituted winter flounder 'antifreeze': preservation of ice growth hysteresis | journal = FEBS Lett. | volume = 430 | issue = 3 | pages = 301–6 |date=July 1998 | pmid = 9688560 | doi = 10.1016/S0014-5793(98)00652-8}}</ref> It is difficult to discern the exact mechanism of binding because of the complex water-ice interface. Currently, attempts to uncover the precise mechanism are being made through use of [[molecular modelling]] programs ([[molecular dynamics]] or the [[Monte Carlo method]]).<ref name="Madura2001" /><ref name="Jorov2004" />
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| == Binding mechanism and antifreeze function ==
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| According to the structure and function study on the antifreeze protein from the fish winter flounder,<ref name=chou>{{cite journal | author = Chou KC | title = Energy-optimized structure of antifreeze protein and its binding mechanism | journal = J. Mol. Biol. | volume = 223 | issue = 2 | pages = 509–17 |date=January 1992 | pmid = 1738160 | doi = 10.1016/0022-2836(92)90666-8| url = }}</ref> the antifreeze mechanism of the type-I AFP molecule was shown to be due to the binding to an ice nucleation structure in a zipper-like fashion through hydrogen bonding of the [[hydroxyl group]]s of its four [[Threonine|Thr]] residues to the oxygens along the <math>[01\overline{1}2]</math> direction in ice lattice, subsequently stopping or retarding the growth of ice pyramidal planes so as to depress the freeze point.<ref name=chou/>
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| The above mechanism can be used to elucidate the structure-function relationship of other antifreeze proteins with the following two common features:
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| # recurrence of a [[Threonine|Thr]] residue (or any other polar amino acid residue whose side-chain can form a hydrogen bond with water) in an 11-amino-acid period along the sequence concerned, and
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| # a high percentage of an [[Alanine|Ala]] residue component therein.<ref name=chou/>
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| == History ==
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| In the 1950s, Canadian scientist Scholander set out to explain how Arctic fish can survive in water colder than the freezing point of their blood. His experiments led him to believe there was “antifreeze” in the blood of Arctic fish.<ref name="Madura2001" /> Then in the late 1960s, animal biologist Arthur DeVries was able to isolate the antifreeze protein through his investigation of Antarctic fish.<ref name="De Vries and Wohlschlag1969">{{cite journal | author = DeVries AL, Wohlschlag DE | title = Freezing resistance in some Antarctic fishes | journal = Science | volume = 163 | issue = 3871 | pages = 1073–5 |date=March 1969 | pmid = 5764871 | doi = 10.1126/science.163.3871.1073 }}</ref> These proteins were later called antifreeze glycoproteins (AFGPs) or antifreeze glycopeptides to distinguish them from newly discovered nonglycoprotein biological antifreeze agents (AFPs). DeVries worked with Robert Feeney (1970) to characterize the chemical and physical properties of antifreeze proteins.<ref name="DeVries1970">{{cite journal | author = DeVries AL, Komatsu SK, Feeney RE | title = Chemical and physical properties of freezing point-depressing glycoproteins from Antarctic fishes | journal = J. Biol. Chem. | volume = 245 | issue = 11 | pages = 2901–8 |date=June 1970 | pmid = 5488456 | doi = }}</ref> In 1992, Griffith ''et al.'' documented their discovery of AFP in winter rye leaves. Around the same time, Urrutia, Duman and Knight (1992) documented thermal hysteresis protein in angiosperms. The next year, Duman and Olsen noted AFPs had also been discovered in over 23 species of [[angiosperms]], including ones eaten by humans.<ref name="Duman and Olsen1993">{{cite journal |author = Duman JG, Olsen TM | year = 1993 | month = | title = Thermal hysteresis protein activity in bacteria, fungi and phylogenetically diverse plants | journal = Cryobiology | volume = 30 | issue = 3 | pages = 322–328 | doi = 10.1006/cryo.1993.1031 }}</ref> As well, they reported their presence in fungi and bacteria.
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| == Name change ==
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| Recent attempts have been made to relabel antifreeze proteins as ice structuring proteins to more accurately represent their function and to dispose of any assumed negative relation between AFPs and automotive antifreeze, [[ethylene glycol]]. These two things are completely separate entities, and show loose similarity only in their function.<ref name="pmid12050776">{{cite journal | author = Clarke CJ, Buckley SL, Lindner N | title = Ice structuring proteins - a new name for antifreeze proteins | journal = Cryo Letters | volume = 23 | issue = 2 | pages = 89–92 | year = 2002 | pmid = 12050776 | doi = }}</ref>
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| == Commercial applications ==
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| Commercially, there appear to be countless applications for antifreeze proteins.<ref>[http://pubs.acs.org/hotartcl/chemtech/99/jun/fletcher.html Antifreeze proteins and their genes: From basic research to business opportunity]</ref> Numerous fields would be able to benefit from the protection of tissue damage by freezing. Businesses are currently investigating the use of these proteins in:
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| * increasing freeze tolerance of crop plants and extending the harvest season in cooler climates
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| * improving farm fish production in cooler climates
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| * lengthening shelf life of frozen foods
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| * improving [[cryosurgery]]
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| * enhancing preservation of tissues for transplant or transfusion in medicine<ref>[http://www.sciencedaily.com/releases/2005/10/051021123223.htm ''Science Daily'']</ref>
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| * therapy for hypothermia
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| == Recent news ==
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| One recent, successful business endeavor has been the introduction of AFPs into ice cream and yogurt products. This ingredient, labelled ice-structuring protein, has been approved by the [[Food and Drug Administration]]. The proteins are isolated from fish and replicated, on a larger scale, in yeast.
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| There is concern from organizations opposed to [[genetically modified organism]]s (GMOs), arguing modified antifreeze proteins may cause inflammation.<ref name="Dortch2006">[http://www.non-gm-farmers.com/news_details.asp?ID=2808 Dortch, Eloise. (2006). Fishy GM yeast used to make ice-cream. Network of Concerned Farmers. Retrieved October 09, 2006]</ref> Intake of AFPs in diet is likely substantial in most northerly and temperate regions already.<ref name="Crevel2002" /> Given the known historic consumption of AFPs, it is safe to conclude their functional properties do not impart any toxicologic or [[allergenic]] effects in humans.<ref name="Crevel2002" />
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| As well, the [[transgenic]] process of ISP production is widely used in society already. [[Insulin]] is produced using this technology. The process does not impact the product; it merely makes production more efficient and prevents the death of many fish who would, otherwise, be killed for the extraction of such protein.
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| Currently, [[Unilever]] incorporates AFPs into some of its American products, including some [[popsicle]]s and a new line of [[Breyers]] Light Double Churned ice cream bars. In ice cream, AFPs allow the production of very creamy, dense, reduced fat ice cream with fewer additives.<ref>[http://www.nytimes.com/2006/07/26/dining/26cream.html Creamy, Healthier Ice Cream? What’s the Catch?]</ref> They control ice crystal growth brought on by thawing on the loading dock or kitchen table which drastically reduces texture quality.<ref name="Regand2006">{{cite journal | author = Regand A, Goff HD | title = Ice recrystallization inhibition in ice cream as affected by ice structuring proteins from winter wheat grass | journal = J. Dairy Sci. | volume = 89 | issue = 1 | pages = 49–57 |date=January 2006 | pmid = 16357267 | doi = 10.3168/jds.S0022-0302(06)72068-9 }}</ref>
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| In November 2009, the [[Proceedings of the National Academy of Sciences]] published the discovery of a molecule in an Alaskan beetle that behaves like AFPs, but is composed of [[Disaccharide|saccharide]]s and [[fatty acid]]s.<ref name="Walters KR Jr, Serianni AS, Sformo T, Barnes BM, Duman JG 2009 20210–5"/>
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| A 2010 study demonstrated the stability of superheated water ice crystals in an AFP solution, showing while the proteins can inhibit freezing, they can also inhibit melting.<ref>{{Cite journal | doi = 10.1016/j.bpj.2009.12.1331 | laysource = Physorg.com | laysummary = http://www.physorg.com/news186669694.html | title = Superheating of Ice in the Presence of Ice Binding Proteins | year = 2010 | last1 = Celik | first1 = Y | last2 = Graham | first2 = LA | last3 = Mok | first3 = YF | last4 = Bar | first4 = M | last5 = Davies | first5 = PL | last6 = Braslavsky | first6 = I | journal = Biophysical Journal | volume = 98 | issue = 3 | pages = 245a}}</ref>
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| == References ==
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| {{Reflist|colwidth=35em}}
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| ==Further reading==
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| {{refbegin|colwidth=35em}}
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| *{{cite journal |last=Haymett |first=A. |authorlink= |author2=Ward, L.|author3=Harding, M. |year=1999 |month= |title=Winter Flounder 'anti-freeze' proteins: Synthesis and ice growth inhibition of analogues that probe the relative importance of hydrophobic and hydrogen bonding interactions |journal=Journal of the American Chemical Society |volume=121 |issue=5 |pages=941–948 |issn=00027863 |url= |accessdate= |quote= |doi=10.1021/ja9801341 }}
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| *{{cite journal |last=Sicheri |first=F. |authorlink= |author2=Yang, D. S. |year=1995 |month= |title=Ice-binding structure and mechanism of an antifreeze protein from winter flounder |journal=Nature |volume=375 |issue=6530 |pages=427–431 |doi=10.1038/375427a0 |url= |accessdate= |quote= |pmid=7760940 }}
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| {{refend}}
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| ==External links==
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| *[http://www.livescience.com/animalworld/060619_freezer_fish.html Cold, Hard Fact: Fish Antifreeze Produced in Pancreas]
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| *[http://www.rcsb.org/pdb/101/motm.do?momID=120 Antifreeze Proteins: Molecule of the Month], by David Goodsell, RCSB Protein Data Bank
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| {{DEFAULTSORT:Antifreeze Protein}}
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| [[Category:Proteins]]
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| [[Category:Cryobiology]]
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