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| {{about|selectivity in chemical systems at equilibrium|kinetic selectivity|Reactivity–selectivity principle}}
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| '''Binding selectivity''' refers to the differing affinities with which different [[Ligand (biochemistry)|ligand]]s bind to a substrate forming a [[Coordination complex|complex]]. 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]]<ref>{{cite book|last=Klotz|first=I.M.|title=Ligand-Receptor Energetics: A Guide for the Perplexed |publisher=Wiley|year=1997|isbn=0-471-17626-5 }}</ref> and in [[Separation process|chemical separation process]]es.
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| == Selectivity coefficient ==
| | These fuzzies may be a small annoyance, but they can make your gym seem unkempt. Macaskill is tackling the Cuillin Ridge in Scotland, not far from where this two-wheeling genius hails from on the Isle of Skye. As a result of this various protective gear manufacturers have also ventured into production of improved design of padded shorts. its also important to look at the design of the bike some bikes are designed for specific porpuses that is to say , there bike s designed for sports , transport porpuses while other motobike are designed for prestige , for leisure porpuses before you go the market ldentify your porpuses why you want tobuy the mountai bike or any bike. With this in mind all you have to do is book the vacation and find the right bike for you and your holiday. <br><br>However, you still have to choose the right Santa Cruz bikes for yourself. Now most people wear gloves whilst they are riding because they keep the hands warm. If you have any type of concerns concerning where and how you can utilize [http://www.tipsofthedays.com/profile/stlus Womens mountain bike sizing.], you can call us at our web-page. From free shipping on all the bikes across the US, the Road Bike Outlet makes consumers happy anywhere within 1 to 6 days. Many riders suggest that if you have less then $700 to spend on a bike you might want to consider a hardtail because full suspension bikes are more costly. 4" wide Schwalbe that can run at 25 psi to behave as passive suspension. <br><br>Technological know-how is advancing very rapidly and manufactures have observed ways to make batteries much more efficient and Eco-pleasant at the very same time along with photo voltaic PV cells getting additional and a lot more effortless and economical to make. Equally expensive can be the tag attached to a lighter-weighted bike. It is meant for leisurely riding, and some mountain biking. The bicycle you have to choose should be under the budget, saving enough for you to buy the necessary accessories for your men's mountain bike, like helmet, gloves, eye gear, etc. However, be careful that any loose ends (from straps or laces) and buckles don't have over, as they can pose a safety hazard if you elect to use toe clips. <br><br>The inaugural Big Bear Gran Fondo takes place on July 26th in Big Bear, with distance options of 20K, 30K, 70K and 100K. This article discusses how to go about buying a mountain bike. Just remember your heart is a muscle and can be developed the more you practice. Now do your comparison-shopping based on five or six available bikes. With Adventure Kerala ( you will enjoy adventure sports like mountaineering, rapelling, rock climbing, river crossing, and a whole lot of adventure activities. <br><br>If you can afford it, a full suspension mountain bike is always worth the purchase. If you can, try and drop off a gutter or curb, standing to allow your knees to absorb the impact. I hope what you will have found in the article with respect to Mongoose mountain bike reviews, together with additionally the particular info regarding mountain bikes, is going to be helpful for you. A twenty-inch wheeled bike are good for longer traveling time. The kids will have a blast exploring any one of the six river parks, and more specifically, walking the suspension bridge across to Fishtrap Park. |
| The concept of selectivity is used to quantify the extent to which a given substrate, A, binds two different ligands, B and C. The simplest case is where the complexes formed have 1:1 [[stoichiometry]]. Then, the two interactions may be characterized by [[equilibrium constant]]s ''K''<sub>AB</sub> and ''K''<sub>AC</sub>.<ref group=note>The constant used here are ''association'' constants. ''Dissociation'' constants are used in some contexts. A dissociation constant is the reciprocal of an association constant.</ref>
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| :<math>A + B \leftrightharpoons AB; K_{AB}=\frac{[AB]}{[A][B]}</math>
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| :<math>A + C \leftrightharpoons AC; K_{AC}=\frac{[AC]}{[A][C]}</math>
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| [..] represents a [[concentration]]. A '''selectivity coefficient''' is defined as the ratio of the two equilibrium constants.
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| :<math>K_{B,C}=\frac{K_{AC}}{K_{AB}}</math>
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| The selectivity coefficient is in fact the equilibrium constant for the displacement reaction
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| :<math>AB + C \leftrightharpoons AC + B; K_{B,C}=\frac{[AC][B]}{[AB][C]}
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| =\frac{K_{AC}[A][B][C]}{K_{AB}[A][B][C]}
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| =\frac{K_{AC}}{K_{AB}}</math>
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| It is easy to show that the same definition applies to complexes of a different stoichiometry, A<sub>p</sub>B<sub>q</sub> and A<sub>p</sub>C<sub>q</sub>. The greater the selectivity coefficient, the more the ligand C will displace the ligand B from the complex formed with the substrate A. An alternative interpretation is that the greater the selectivity coefficient, the lower the concentration of C that is needed to displace B from AB. Selectivity coefficients are determined experimentally by measuring the two equilibrium constants, ''K''<sub>AB</sub> and ''K''<sub>AC</sub>.
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| == Applications ==
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| === Biochemistry ===
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| {{main|Receptor (biochemistry)}}
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| In biochemistry the substrate is known as a receptor. A receptor is a [[protein]] molecule, embedded in either the [[plasma membrane]] or the [[cytoplasm]] of a cell, to which one or more specific kinds of signalling molecules may bind. A [[Ligand (biochemistry)|ligand]] may be a [[peptide]] or another small molecule, such as a [[neurotransmitter]], a [[hormone]], a pharmaceutical drug, or a toxin. The specificity of a receptor is determined by its spatial geometry and the way it [[binding (molecular)|binds]] to the ligand through [[Noncovalent bonding|non-covalent interactions]], such as [[hydrogen bond]]ing or [[Van der Waals force]]s.<ref>{{cite book|last=Foreman|first=J.C.|coauthors=Johansen, T. (Editors)|title=Textbook of receptor pharmacology|publisher=CRC Press|location=Boca Raton, Fla.|year=2003|edition=2nd.|isbn=0-8493-1029-6}}</ref>
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| If a receptor can be isolated a synthetic drug can be developed either to stimulate the receptor, an [[agonist]] or to block it, an [[antagonist]]. The [[stomach ulcer]] drug [[cimetidine]] was developed as an [[H2 antagonist|H<sub>2</sub> antagonist]] by chemically engineering the molecule for maximum specificity to an isolated tissue containing the receptor. The further use of [[quantitative structure-activity relationship]]s (QSAR) led to the development of other agents such as [[ranitidine]].
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| It is important to note that "selectivity" when referring to a drug is relative and not absolute. For example, in a higher dose, a specific drug molecule may also bind to other receptors than those said to be "selective".
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| === Chelation therapy ===
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| {{main|Chelation therapy}}
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| [[File:Deferiprone.svg|thumb|75px|Deferiprone]]
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| [[File:Penicillamine structure.png|thumb|75px|Penicillamine]]
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| Chelation therapy is a form of medical treatment in which a [[chelate|chelating ligand]]<ref group=note>The term "ligand" here refers to binding to a metal. In the definition of selectivity coefficient this "ligand" is in fact the substrate and ligand in that definition is the metal ion.</ref> is used to selectively remove a metal from the body. When the metal exists as a divalent ion, such as with [[lead]], Pb<sup>2+</sup> or [[mercury (element)|mercury]], Hg<sup>2+</sup> selectivity against [[calcium]], Ca<sup>2+</sup> and [[magnesium]], Mg<sup>2+</sup>, is essential in order that the treatment does not remove essential metals.<ref>{{cite book|last=Walker|first=M.|coauthors=Shah, H.H.|title=Everything you should know about chelation therapy |publisher=Keats Pub.|location=New Canaan, Conn.|year=1997|edition=4th|isbn=0-87983-730-6 }}</ref>
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| Selectivity is determined by various factors. In the case of [[iron overload]], which may occur in individuals with β-[[thalessemia]] who have received [[blood transfusion]]s, the target metal ion is in the +3 [[oxidation state]] and so forms stronger complexes than the divalent ions. It also forms stronger complexes with oxygen-donor ligands than with nitrogen-donor ligands. [[deferoxamine]], a naturally occurring [[siderophore]] produced by the actinobacter ''Streptomyces pilosus'' and was used initially as a chelation therapy agent. Synthetic siderophores such as [[deferiprone]] and [[deferasirox]] have been developed, using the known structure of deferoxamine as a starting point.<ref>{{Cite journal
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| | doi = 10.1021/cr00097a011 | volume = 89
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| | year = 1989 | issue = 7 | pages = 1563–1579 | last = Miller | first = Marvin J.
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| | title = Syntheses and therapeutic potential of hydroxamic acid-based siderophores and analogs | journal = Chemical Reviews}}</ref> Chelation occurs with the two oxygen atoms.
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| [[Wilson's disease]] is caused by a defect in [[copper]] metabolism which results in accumulation of copper metal in various organs of the body. The target ion in this case is divalent, Cu<sup>2+</sup>. This ion is classified as borderline in the scheme of Ahrland, Chatt and Davies.<ref>{{cite journal|last=Ahrland|first=S.
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| |coauthors=Chatt, J.; Davies, N.R.|year=1958|title=The relative affinities of ligand atoms for acceptor molecules and ions|journal=Quart. Rev.|volume=12|pages=265–276|doi=10.1039/QR9581200265|issue=3}}</ref> This means that it forms roughly equally strong complexes with ligands whose donor atoms are N, O or F as with ligands whose donor atoms are P, S or Cl. [[Penicillamine]], which contains nitrogen and sulphur donor atoms, is used as this type of ligand binds more strongly to copper ions than to calcium and magnesium ions.
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| Treatment of poisoning by heavy metals such as lead and mercury is more problematical, because the ligands used do not have high specificity relative to calcium. For example, [[EDTA]] may be administered as a calcium salt to reduce the removal of calcium from bone together with the heavy metal.
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| === Chromatography ===
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| {{main|Chromatography}}
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| In column chromatography a mixture of substances is dissolved in a mobile phase and passed over a stationary phase in a column. A selectivity factor is defined as the ratio of [[distribution coefficient]]s, which describe the equilibrium distribution of an [[analyte]] between the stationary phase and the mobile phase. The selectivity factor is equal to the selectivity coefficient with the added assumption that the [[activity (chemistry)|activity]] of the stationary phase, the substrate in this case, is equal to 1, the standard assumption for a pure phase.<ref>{{cite book |last=Skoog |first=D.A |coauthors=West, D.M.; Holler, J.F.; Crouch, S.R. |title=Fundamentals of Analytical Chemistry |publisher=Thomson Brooks/Cole |year=2004 |edition=8th |isbn=0-03-035523-0}} Section 30E</ref> The resolution of a chromatographic column, ''R''<sub>S</sub> is related to the selectivity factor by:
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| :<math>R_S=\frac{\sqrt N}{4}\left(\frac{\alpha-1}{\alpha}\right)\left(\frac{k_B}{1+k_B}\right)
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| </math>
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| where α is selectivity factor, ''N'' is the number of [[theoretical plate]]s ''k''<sub>A</sub> and ''k''<sub>B</sub> are the [[retention factor]]s of the two analytes. Retention factors are proportional to distribution coefficients. In practice substances with a selectivity factor very close to 1 can be separated. This is particularly true in [[gas-liquid chromatography]] where column lengths up to 60 m are possible, providing a very large number of theoretical plates.
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| In ion-exchange chromatography the selectivity coefficient is defined in a slightly different way<ref>Selectivity coefficient in ion exchange chromatography,{{cite web|url=http://www.iupac.org/goldbook/S05566.pdf|title=http://www.iupac.org/goldbook/S05566.pdf|accessdate=10 March 2010}}</ref>
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| === Solvent extraction ===
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| {{Main|Solvent extraction}}
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| Solvent extraction<ref>{{cite journal|last=Rice|first=N.M.|coauthors=Irving, H. M. N. H.;Leonard, M.A|year=1993|title=Nomenclature for liquid-liquid distribution (solvent extraction)|journal=Pure Appl. Chem. |publisher=IUPAC|volume=65|issue=11|pages=2373–2396|doi=10.1351/pac199365112373}}</ref> is used to extract individual [[lanthanoid]] elements from the mixtures found in nature in ores such as [[monazite]]. In one process, the metal ions in aqueous solution are made to form complexes with [[tributylphosphate]] (TBP), which are extracted into an organic solvent such as [[kerosene]]. Complete separation is effected by using a [[countercurrent exchange]] method. A number of cells are arranged as a [[cascade (chemical engineering)|cascade]]. After equilibration, the aqueous component of each cell is transferred to the previous cell and the organic component is transferred to the next cell, which initially contains only water. In this way the metal ion with the most stable complex passes down the cascade in the organic phase and the metal with the least stable complex passes up the cascade in the aqueous phase.<ref>{{cite book|last=Rydberg |first=J.|coauthors=Musikas, C;Choppin, G.R. (Editors)|title=Solvent Extraction Principles and Practice (|publisher=CRC Press|location=Boca Raton, Fla. |year=2004|edition=2nd.|isbn=0-8247-5063-2 }}</ref>
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| If solubility in the organic phase is not an issue, a selectivity coefficient is equal to the ratio of the [[stability constants of complexes|stability constants]] of the TBP complexes of two metal ions. For lanthanoid elements which are adjacent in the [[periodic table]] this ratio is not much greater than 1, so many cells are needed in the cascade.
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| === Chemical sensors ===
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| [[File:Sensing.png|thumb|250px|right|Types of Chemosensors. <span style="color:black">(1.)</span> Indicator-spacer-receptor (ISR) <span style="color:black">(2.)</span> Indicator-Displacement Assay (IDA)]]
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| A potentiometric selectivity coefficient defines the ability of an [[ion-selective electrode]] to
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| distinguish one particular ion from others. The selectivity coefficient, K<sub>B,C</sub> is evaluated by means of the emf response of the ion-selective electrode in mixed solutions of the primary ion, B, and interfering ion, C (fixed interference method) or less desirably, in separate solutions of B and C (separate
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| solution method).<ref>{{cite journal|last=Buck|first=R. P.|coauthors=Linder, E.|year=1994|title=Recommendations for nomenclature of ion-selective electrodes|journal=Pure App. Chem.|publisher=IUPAC|volume=66|issue=12|pages=2527–2536|doi=10.1351/Pac199466122527}}</ref> For example, a [[potassium]] ion-selective [[ion-selective electrode|membrane electrode]] utilizes the naturally occurring macrocyclic [[antibiotic]] [[valinomycin]]. In this case the cavity in the macrocyclic ring is just the right size to encapsulate the potassium ion, but too large to bind the sodium ion, the most likely interference, strongly.
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| [[host-guest chemistry#Sensing|Chemical sensors]]<ref>{{cite book|last=Cattrall|first=R.W.|title=Chemical sensors|publisher=Oxford University Press|year=1997|isbn=0-19-850090-4 }}</ref> are being developed for specific target molecules and ions in which the target (guest) form a complex with a sensor (host). The sensor is designed to be an excellent match in terms of the size and shape of the target in order to provide for the maximum binding selectivity. An indicator is associated with the sensor which undergoes a change when the target forms a complex with the sensor . The indicator change is usually a colour change (gray to yellow in the illustration) seen in [[absorbance]] or, with greater sensitivity, [[luminescence]]. The indicator may be attached to the sensor via a spacer, in the ISR arrangement, or it may be displaced from the sensor, IDA arrangement.
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| == See also ==
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| * [[Binding (molecular)|Binding]]
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| * [[Affinity (pharmacology)|Affinity]]
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| *[[Functional selectivity]]
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| == Notes ==
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| {{reflist|group=note}}
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| == References ==
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| {{Reflist|2}}
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| {{chemical equilibria}}
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| [[Category:Equilibrium chemistry]]
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| [[Category:Pharmacology]]
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These fuzzies may be a small annoyance, but they can make your gym seem unkempt. Macaskill is tackling the Cuillin Ridge in Scotland, not far from where this two-wheeling genius hails from on the Isle of Skye. As a result of this various protective gear manufacturers have also ventured into production of improved design of padded shorts. its also important to look at the design of the bike some bikes are designed for specific porpuses that is to say , there bike s designed for sports , transport porpuses while other motobike are designed for prestige , for leisure porpuses before you go the market ldentify your porpuses why you want tobuy the mountai bike or any bike. With this in mind all you have to do is book the vacation and find the right bike for you and your holiday.
However, you still have to choose the right Santa Cruz bikes for yourself. Now most people wear gloves whilst they are riding because they keep the hands warm. If you have any type of concerns concerning where and how you can utilize Womens mountain bike sizing., you can call us at our web-page. From free shipping on all the bikes across the US, the Road Bike Outlet makes consumers happy anywhere within 1 to 6 days. Many riders suggest that if you have less then $700 to spend on a bike you might want to consider a hardtail because full suspension bikes are more costly. 4" wide Schwalbe that can run at 25 psi to behave as passive suspension.
Technological know-how is advancing very rapidly and manufactures have observed ways to make batteries much more efficient and Eco-pleasant at the very same time along with photo voltaic PV cells getting additional and a lot more effortless and economical to make. Equally expensive can be the tag attached to a lighter-weighted bike. It is meant for leisurely riding, and some mountain biking. The bicycle you have to choose should be under the budget, saving enough for you to buy the necessary accessories for your men's mountain bike, like helmet, gloves, eye gear, etc. However, be careful that any loose ends (from straps or laces) and buckles don't have over, as they can pose a safety hazard if you elect to use toe clips.
The inaugural Big Bear Gran Fondo takes place on July 26th in Big Bear, with distance options of 20K, 30K, 70K and 100K. This article discusses how to go about buying a mountain bike. Just remember your heart is a muscle and can be developed the more you practice. Now do your comparison-shopping based on five or six available bikes. With Adventure Kerala ( you will enjoy adventure sports like mountaineering, rapelling, rock climbing, river crossing, and a whole lot of adventure activities.
If you can afford it, a full suspension mountain bike is always worth the purchase. If you can, try and drop off a gutter or curb, standing to allow your knees to absorb the impact. I hope what you will have found in the article with respect to Mongoose mountain bike reviews, together with additionally the particular info regarding mountain bikes, is going to be helpful for you. A twenty-inch wheeled bike are good for longer traveling time. The kids will have a blast exploring any one of the six river parks, and more specifically, walking the suspension bridge across to Fishtrap Park.