Array ( [0] => {{short description|Motion of charged particles in electric field}} [1] => {{For|the process of administering medicine|Iontophoresis}} [2] => {{other uses}} [3] => [[File:Motion by electrophoresis of a charged particle.svg|thumb|300px|1. Illustration of electrophoresis]] [4] => {{anchor| Fig2}} [[File:Retardation Force.svg|thumb|300px|2. Illustration of electrophoresis retardation]] [5] => [6] => In [[chemistry]]''', electrophoresis''' is the motion of [[Electric charge|charged]] [[Interface and colloid science|dispersed particles]] or [[Solvation|dissolved]] [[Ion|charged]] [[molecules]] relative to a fluid under the influence of a spatially uniform [[electric field]]. As a rule, these are [[zwitterion]]s. Electrophoresis of positively charged particles or molecules ([[cation]]s) is sometimes called '''cataphoresis''', while electrophoresis of negatively charged particles or molecules (anions) is sometimes called '''anaphoresis'''.{{cite book |first=J. |last=Lyklema |title= Fundamentals of Interface and Colloid Science |volume= 2 |page=3.208 |year=1995}}{{cite book |first=R.J. |last=Hunter |title=Foundations of Colloid Science |publisher=Oxford University Press |year=1989}}{{cite book |first1=S.S. |last1=Dukhin |first2=B.V. |last2=Derjaguin |title=Electrokinetic Phenomena |publisher=J. Wiley and Sons |year=1974}}{{cite book |first1=W.B. |last1=Russel |first2=D.A. |last2=Saville |first3=W.R. |last3=Schowalter |title=Colloidal Dispersions |url=https://archive.org/details/colloidaldispers0000russ |url-access=registration |publisher=Cambridge University Press |year=1989|isbn=9780521341882 }}{{cite book |first=H.R. |last=Kruyt |title=Colloid Science |publisher=Elsevier |volume=1, Irreversible systems |year=1952}}{{cite book | last1=Dukhin | first1=A.S. | last2=Goetz | first2=P.J. |title=Characterization of liquids, nano- and micro- particulates and porous bodies using Ultrasound | publisher= Elsevier | year=2017 [7] => |url= https://www.elsevier.com/books/characterization-of-liquids-dispersions-emulsions-and-porous-materials-using-ultrasound/dukhin/978-0-444-63908-0 |isbn= 978-0-444-63908-0}}{{Cite journal |last=Anderson |first=J.L.|date=January 1989 |title=Colloid Transport by Interfacial Forces |journal=Annual Review of Fluid Mechanics |language=en |volume=21 |issue=1 |pages=61–99 |doi= 10.1146/annurev.fl.21.010189.000425 |issn=0066-4189 |bibcode=1989AnRFM..21...61A}}{{cite book |author=Michov, B. |year=2022 |title=Electrophoresis Fundamentals: Essential Theory and Practice |url=https://www.degruyter.com/document/doi/10.1515/9783110761641/html |url-access= |publisher=De Gruyter, ISBN 9783110761627|doi=10.1515/9783110761641 |isbn=9783110761641 }}. [8] => [9] => [[Drop (liquid)|Liquid droplet]] electrophoresis is significantly different from the classic particle electrophoresis because of droplet characteristics such as a mobile surface charge and the nonrigidity of the interface. Also, the liquid–liquid system, where there is an interplay between the hydrodynamic and electrokinetic forces in both phases, adds to the complexity of electrophoretic motion.{{cite journal |last1=Rashidi |first1=Mansoureh |title=Mechanistic studies of droplet electrophoresis: A review |journal=Electrophoresis |date=2021 |volume=42 |issue=7–8 |pages=869–880 |doi=10.1002/elps.202000358 }} [10] => [11] => Electrophoresis is the basis for [[Analytical chemistry|analytical techniques]] used in [[biochemistry]] for separating particles, molecules, or ions by [[Molecular mass|size]], charge, or [[Intermolecular force|binding affinity]].{{cite book |first=P. |last=Malhotra |title= Analytical Chemistry: Basic Techniques and Methods |publisher=Springer, ISBN 9783031267567 |volume= |page=346 |year=2023}} [12] => [13] => Biochemist [[Arne Tiselius]] won the [[Nobel Prize in Chemistry]] in 1948 "for his research on [[electrophoresis]] and [[adsorption]] analysis, especially for his discoveries concerning the complex nature of the [[Serum protein electrophoresis|serum proteins]]."{{Cite web |title=The Nobel Prize in Chemistry 1948 |url=https://www.nobelprize.org/prizes/chemistry/1948/summary/ |access-date=2023-11-03 |website=NobelPrize.org |language=en-US}} [14] => [15] => In principle, '''electrophoresis''' is used in laboratories to separate [[macromolecule]]s based on charge.{{cite journal [16] => |journal=Electroanalysis [17] => |date=2006 [18] => |volume=18 [19] => |pages=103–6 [20] => |title=Comparison of the electrochemical behavior of the high molecular mass cadmium proteins in Arabidopsis thaliana and in vegetable plants on using preparative native continuous polyacrylamide gel electrophoresis (PNC-PAGE) [21] => |author=Kastenholz B. [22] => |doi=10.1002/elan.200403344 [23] => |issue=1 }} [24] => The technique normally applies a [[QPNC-PAGE#Method|negative charge]] so proteins move towards a positive charge called [[anode]]. It is used extensively in [[DNA]], [[RNA]] and [[protein]] analysis.{{cite journal [25] => |journal=Introduction to Biophysical Methods for Protein and Nucleic Acid Research [26] => |date=1995 [27] => |volume= [28] => |pages=53–109 [29] => |title=Chapter 2 – Electrophoretic Methods [30] => |author=Garfin D.E. [31] => |url=https://doi.org/10.1016/B978-012286230-4/50003-1 [32] => |doi=10.1016/B978-012286230-4/50003-1 [33] => |pmid= [34] => }} [35] => [36] => [37] => == History == [38] => {{excerpt|History of electrophoresis}} [39] => [40] => == Theory == [41] => [42] => Suspended particles have an [[electric surface charge]], strongly affected by surface adsorbed species, [43] => {{cite journal [44] => | last1=Hanaor [45] => | first1=D.A.H. [46] => | last2=Michelazzi [47] => | first2=M. [48] => | last3=Leonelli [49] => | first3=C. [50] => | last4=Sorrell [51] => | first4=C.C. [52] => | title= The effects of carboxylic acids on the aqueous dispersion and electrophoretic deposition of ZrO2 [53] => | journal= Journal of the European Ceramic Society [54] => | year=2012 [55] => | volume=32 [56] => | issue=1 [57] => | pages=235–244 [58] => | doi= 10.1016/j.jeurceramsoc.2011.08.015| arxiv=1303.2754 [59] => | s2cid=98812224 [60] => }} on which an external electric field exerts an [[electrostatic]] [[Coulomb force]]. According to the [[Double layer (interfacial)|double layer]] theory, all surface charges in fluids are screened by a [[diffuse layer]] of ions, which has the same absolute charge but opposite sign with respect to that of the surface charge. The [[electric field]] also exerts a force on the ions in the diffuse layer which has direction opposite to that acting on the [[surface charge]]. This latter force is not actually applied to the particle, but to the [[ions]] in the diffuse layer located at some distance from the particle surface, and part of it is transferred all the way to the particle surface through [[Viscosity|viscous]] [[Stress (physics)|stress]]. This part of the force is also called electrophoretic retardation force, or ERF in short. [61] => When the electric field is applied and the charged particle to be analyzed is at steady movement through the diffuse layer, the total resulting force is zero: [62] => : F_{\text{tot}} = 0 = F_{\text{el}} + F_{\mathrm{f}} + F_{\text{ret}} [63] => [64] => Considering the [[Drag (physics)|drag]] on the moving particles due to the [[viscosity]] of the dispersant, in the case of low [[Reynolds number]] and moderate electric field strength ''E'', the [[drift velocity]] of a dispersed particle ''v'' is simply proportional to the applied field, which leaves the electrophoretic [[Electrical mobility|mobility]] μe defined as:{{cite journal | arxiv=1303.2742 | doi=10.1016/j.jeurceramsoc.2010.12.017 | title=Anodic aqueous electrophoretic deposition of titanium dioxide using carboxylic acids as dispersing agents | year=2011 | last1=Hanaor | first1=Dorian | last2=Michelazzi | first2=Marco | last3=Veronesi | first3=Paolo | last4=Leonelli | first4=Cristina | last5=Romagnoli | first5=Marcello | last6=Sorrell | first6=Charles | journal=Journal of the European Ceramic Society | volume=31 | issue=6 | pages=1041–1047 | s2cid=98781292 }} [65] => [66] => :\mu_e = {v \over E}. [67] => [68] => The most well known and widely used theory of electrophoresis was developed in 1903 by [[Marian Smoluchowski|Marian Smoluchowski]]:{{cite journal |first=M. |last=von Smoluchowski |journal=Bull. Int. Acad. Sci. Cracovie |volume=184 |year=1903 |title=Contribution à la théorie de l'endosmose électrique et de quelques phénomènes corrélatifs}} [69] => [70] => :\mu_e = \frac{\varepsilon_r\varepsilon_0\zeta}{\eta}, [71] => [72] => where εr is the [[dielectric constant]] of the [[dispersion medium]], ε0 is the [[Vacuum permittivity|permittivity of free space]] (C2 N−1 m−2), η is [[dynamic viscosity]] of the dispersion medium (Pa s), and ζ is [[zeta potential]] (i.e., the [[electrokinetic potential]] of the [[slipping plane]] in the [[double layer (interfacial)|double layer]], units mV or V). [73] => [74] => The Smoluchowski theory is very powerful because it works for [[dispersed particles]] of any [[shape]] at any [[concentration]]. It has limitations on its validity. For instance, it does not include [[Debye length]] κ−1 (units m). However, Debye length must be important for electrophoresis, as follows immediately from Figure 2, [75] => [[#Fig2|"Illustration of electrophoresis retardation"]]. [76] => Increasing thickness of the double layer (DL) leads to removing the point of retardation force further from the particle surface. The thicker the DL, the smaller the retardation force must be. [77] => [78] => Detailed theoretical analysis proved that the Smoluchowski theory is valid only for sufficiently thin DL, when particle radius ''a'' is much greater than the Debye length: [79] => [80] => : a \kappa \gg 1. [81] => [82] => This model of "thin double layer" offers tremendous simplifications not only for electrophoresis theory but for many other electrokinetic theories. This model is valid for most [[aqueous]] systems, where the Debye length is usually only a few [[nanometers]]. It only breaks for nano-colloids in solution with [[ionic strength]] close to water. [83] => [84] => The Smoluchowski theory also neglects the contributions from [[surface conductivity]]. This is expressed in modern theory as condition of small [[Dukhin number]]: [85] => [86] => : Du \ll 1 [87] => [88] => In the effort of expanding the range of validity of electrophoretic theories, the opposite asymptotic case was considered, when Debye length is larger than particle radius: [89] => [90] => : a \kappa < \!\, 1. [91] => [92] => Under this condition of a "thick double layer", [[Erich Hückel]]{{cite journal |first=E. |last=Hückel |journal=Phys. Z. |volume=25 |page=204|title=Die kataphorese der kugel |year=1924}} predicted the following relation for electrophoretic mobility: [93] => [94] => :\mu_e = \frac{2\varepsilon_r\varepsilon_0\zeta}{3\eta}. [95] => [96] => This model can be useful for some [[nanoparticle]]s and non-polar fluids, where Debye length is much larger than in the usual cases. [97] => [98] => There are several analytical theories that incorporate [[surface conductivity]] and eliminate the restriction of a small Dukhin number, pioneered by [[Theodoor Overbeek]]{{cite journal |first=J.Th.G |last=Overbeek |journal=Koll. Bith. |page=287 |title=Theory of electrophoresis — The relaxation effect|year=1943}} and F. Booth.{{cite journal |first=F. |last=Booth |journal=Nature |volume=161 |issue=4081 |pages=83–86 |year=1948|bibcode = 1948Natur.161...83B |doi = 10.1038/161083a0 |pmid=18898334|title=Theory of Electrokinetic Effects |s2cid=4115758 |doi-access=free }} Modern, rigorous theories valid for any [[Zeta potential]] and often any ''aκ'' stem mostly from Dukhin–Semenikhin theory.Dukhin, S.S. and Semenikhin N.V. "Theory of double layer polarization and its effect on electrophoresis", Koll.Zhur. USSR, volume 32, page 366, 1970. [99] => [100] => In the '''thin double layer''' limit, these theories confirm the numerical solution to the problem provided by Richard W. O'Brien and Lee R. White.{{cite journal |first=R.W. |last=O'Brien |author2=L.R. White |title=Electrophoretic mobility of a spherical colloidal particle|journal=J. Chem. Soc. Faraday Trans. |volume=2 |issue=74 |page=1607 |year=1978|doi=10.1039/F29787401607 }} [101] => [102] => For modeling more complex scenarios, these simplifications become inaccurate, and the electric field must be modeled spatially, tracking its magnitude and direction. [[Poisson's equation]] can be used to model this spatially-varying electric field. Its influence on fluid flow can be modeled with the [[Stokes' law|Stokes law]],{{cite journal | last1=Paxton | first1=Walter F. | last2=Sen | first2=Ayusman | last3=Mallouk | first3=Thomas E. | title=Motility of Catalytic Nanoparticles through Self-Generated Forces | journal=Chemistry - A European Journal | publisher=Wiley | volume=11 | issue=22 | date=2005-11-04 | issn=0947-6539 | doi=10.1002/chem.200500167 | pages=6462–6470| pmid=16052651 }} while transport of different ions can be modeled using the [[Nernst–Planck equation]]. This combined approach is referred to as the Poisson-Nernst-Planck-Stokes equations.{{cite journal | last1=Moran | first1=Jeffrey L. | last2=Posner | first2=Jonathan D. | title=Electrokinetic locomotion due to reaction-induced charge auto-electrophoresis | journal=Journal of Fluid Mechanics | publisher=Cambridge University Press (CUP) | volume=680 | date=2011-06-13 | issn=0022-1120 | doi=10.1017/jfm.2011.132 | pages=31–66| bibcode=2011JFM...680...31M | s2cid=100357810 }} This approach has been validated the electrophoresis of particles. [103] => [104] => [105] => [106] => ==See also== [107] => {{cmn|colwidth=30em| [108] => *[[Affinity electrophoresis]] [109] => *[[Electrophoretic deposition]] [110] => *[[Electronic paper]] [111] => *[[Capillary electrophoresis]] [112] => *[[Dielectrophoresis]] [113] => *[[Free-flow electrophoresis]] [114] => *[[Electroblotting]] [115] => *[[Gel electrophoresis]] [116] => *[[Gel electrophoresis of nucleic acids]] [117] => *[[Gel electrophoresis of proteins]] [118] => *[[History of electrophoresis]] [119] => *[[Gel electrophoresis#History|History of gel electrophoresis]] [120] => *[[Immunoelectrophoresis]] [121] => *[[Isoelectric focusing]] [122] => *[[Isotachophoresis]] [123] => *[[Nonlinear frictiophoresis]] [124] => *[[Pulsed-field gel electrophoresis]] [125] => *[[Stokes flow]] [126] => [127] => }} [128] => [129] => ==References== [130] => {{Reflist}} [131] => [132] => ==Further reading== [133] => * {{cite book |author=Voet and Voet |year=1990 |title=Biochemistry |url=https://archive.org/details/biochemistry00voet |url-access=registration |publisher=John Wiley & Sons}} [134] => * {{cite journal |first=G.C. |last=Jahn |author2=D.W. Hall |author3=S.G. Zam |year=1986 |title=A comparison of the life cycles of two ''Amblyospora'' (Microspora: ''Amblyosporidae'') in the mosquitoes ''Culex salinarius'' and ''Culex tarsalis'' Coquillett |journal=J. Florida Anti-Mosquito Assoc. |volume=57 |pages=24–27}} [135] => * {{cite journal |first=M.N. |last=Khattak |author2=R.C. Matthews |year=1993 |title=Genetic relatedness of ''Bordetella'' species as determined by macrorestriction digests resolved by pulsed-field gel electrophoresis |journal=Int. J. Syst. Bacteriol. |volume=43 |issue=4 |pages=659–64|pmid=8240949 |doi=10.1099/00207713-43-4-659|doi-access=free }} [136] => * {{cite journal |first=D.P.J. |last=Barz |author2=P. Ehrhard |year=2005 |title=Model and verification of electrokinetic flow and transport in a micro-electrophoresis device |journal=Lab Chip |volume=5 |issue=9 |pages=949–958|pmid=16100579 |doi=10.1039/b503696h }} [137] => * {{cite journal |first=J. |last=Shim |author2=P. Dutta |author3=C.F. Ivory |year=2007 |title=Modeling and simulation of IEF in 2-D microgeometries |journal=[[Electrophoresis (journal)|Electrophoresis]] |volume=28 |issue=4 |pages=527–586|doi=10.1002/elps.200600402 |pmid=17253629 |s2cid=23274096 }} [138] => [139] => ==External links== [140] => {{Commons}} [141] => {{Wiktionary}} [142] => * [http://web.med.unsw.edu.au/phbsoft/mobility_listings.htm List of relative mobilities] [143] => [144] => {{electrophoresis}} [145] => {{Authority control}} [146] => [147] => [[Category:Electrophoresis| ]] [148] => [[Category:Colloidal chemistry]] [149] => [[Category:Biochemical separation processes]] [150] => [[Category:Electroanalytical methods]] [151] => [[Category:Instrumental analysis]] [152] => [[Category:Laboratory techniques]] [] => )
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Electrophoresis

Electrophoresis is a laboratory technique used for separating and analyzing molecules based on their size and charge. This process involves applying an electric field to a solid or gel matrix containing the molecules, causing them to migrate at different rates towards the positive or negative electrode.

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This process involves applying an electric field to a solid or gel matrix containing the molecules, causing them to migrate at different rates towards the positive or negative electrode. The molecules are separated based on their mobility, with smaller and more negatively charged molecules moving faster than larger and less charged ones. Electrophoresis has a wide range of applications in various scientific disciplines, including biochemistry, molecular biology, genetics, and clinical diagnostics. It is commonly used to separate proteins, nucleic acids (DNA and RNA), and carbohydrates, allowing for the identification and characterization of these molecules. In addition, electrophoresis can be used to analyze protein-protein interactions, enzyme activity, and DNA sequencing. There are several types of electrophoresis techniques, such as agarose gel electrophoresis, polyacrylamide gel electrophoresis, capillary electrophoresis, and isoelectric focusing. Each technique has its own advantages and is suited for different applications. Electrophoresis can be further enhanced by incorporating other methods like Western blotting, Southern blotting, and gel staining, which allow for specific detection and analysis of molecules after separation. Despite its widespread use, electrophoresis has its limitations. It is not suitable for separating molecules of similar size or charge, and the process can be time-consuming. However, the technique continues to be instrumental in numerous research and diagnostic settings due to its versatility, simplicity, and reliability.

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