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SDS-PAGE 1

SDS-PAGE

Picture of an SDS-PAGE. The molecular marker is in the leftlane

SDS-PAGE, sodium dodecyl sulfate polyacrylamide gelelectrophoresis, is a technique widely used inbiochemistry, forensics, genetics and molecular biology toseparate proteins according to their electrophoretic mobility(a function of length of polypeptide chain or molecularweight). SDS gel electrophoresis of samples havingidentical charge per unit mass due to binding of SDS resultsin fractionation by size.

Procedure

Tissue preparation

Samples may be taken from whole tissue or from cellculture. In most cases, solid tissues are first broken downmechanically using a blender (for larger sample volumes),using a homogenizer (smaller volumes), or by sonication.Cells may also be broken open by one of the abovemechanical methods. However, it should be noted thatbacteria, virus or environmental samples can be the source of protein and thus Western blotting is not restricted tocellular studies only.

A combination of biochemical and mechanical techniques – including various types of filtration and centrifugation –can be used to separate different cell compartments and organelles.The solution of proteins to be analyzed is mixed with SDS, an anionic detergent which denatures secondary andnon–disulfide–linked tertiary structures, and applies a negative charge to each protein in proportion to its mass.Heating the samples to at least 60 degrees C shakes up the molecules, helping SDS to bind. [1] [2] [3] [4]

A tracking dye may be added to the protein solution (of a size smaller than protein) to allow the experimenter totrack the progress of the protein solution through the gel during the electrophoretic run.

SDS-PAGE 2

Preparing acrylamide gelsThe gels generally consist of acrylamide, bisacrylamide, SDS, and a Tris-Cl buffer with adjusted pH. The solution isdegassed under a vacuum to prevent air bubbles during polymerization. [5] Ammonium persulfate and TEMED areadded when the gel is ready to be polymerized. The separating or resolving gel is usually more basic and has ahigher polyacrylamide content than the loading gel. [6]

Gels are polymerized in a gel caster. First the separating gel is poured and allowed to polymerize. Next a thin layerof isopropanol is added. Next the loading gel is poured and a comb is placed to create the wells. After the loading gelis polymerized the comb can be removed and the gel is ready for electrophoresis.

SDS-PAGE 3

ElectrophoresisFirst the anode and cathode buffers are prepared. The anode buffer usually contains Tris-Cl, distilled deionized waterand is adjusted to a higher pH than the cathode buffer. The cathode buffer contains SDS, Tris, Tricine, and distilleddeionized water. [7] [8]

The electrophoresis apparatus is set up with cathode buffer covering the gel in the negative electrode chamber, andanode buffer in the lower positive electrode chamber. Next, the denatured sample proteins are added to the wells oneend of the gel with a syringe or pipette. Finally, the apparatus is hooked up to a power source under appropriaterunning conditions to separate the protein bands.

An electric field is applied across the gel, causing the negatively-charged proteins to migrate across the gel towardsthe positive (+) electrode (anode). Depending on their size, each protein will move differently through the gel matrix:short proteins will more easily fit through the pores in the gel, while larger ones will have more difficulty (theyencounter more resistance). After a set amount of time (usually a few hours- though this depends on the voltageapplied across the gel; higher voltages run faster but tend to produce somewhat poorer resolution), the proteins willhave differentially migrated based on their size; smaller proteins will have traveled farther down the gel, while largerones will have remained closer to the point of origin. Therefore, proteins may be separated roughly according to size(and therefore, molecular weight), certain glycoproteins behave anomalously on SDS gels.

SDS-PAGE 4

Staining

Two SDS-PAGE-gels after a completed run

Following electrophoresis, the gel may be stained (most commonlywith Coomassie Brilliant Blue R-250 or silver stain), allowingvisualization of the separated proteins, or processed further (e.g.Western blot). After staining, different proteins will appear as distinctbands within the gel. It is common to run molecular markers of knownmolecular weight in a separate lane in the gel, in order to calibrate thegel and determine the weight of unknown proteins by comparing thedistance traveled relative to the marker. The gel is actually formedbecause the acrylamide solution contains a small amount, generallyabout 1 part in 35 of bisacrylamide, which can form cross-linksbetween two polyacrylamide molecules. The ratio of acrylamide to

bisacrylamide can be varied for special purposes. The acrylamide concentration of the gel can also be varied,generally in the range from 5% to 25%. Lower percentage gels are better for resolving very high molecular weightproteins, while much higher percentages are needed to resolve smaller proteins. Determining how much of thevarious solutions to mix together to make gels of particular acrylamide concentration can be done on line [9]

Gel electrophoresis is usually the first choice as an assay of protein purity due to its reliability and ease. Thepresence of SDS and the denaturing step causes proteins to be separated solely based on size. False negatives andpositives are possible. A comigrating contaminant can appear as the same band as the desired protein. Thiscomigration could also cause a protein to run at a different position or to not be able to penetrate the gel. This is whyit is important to stain the entire gel including the stacking section. Coomassie Brilliant Blue will also bind with lessaffinity to glycoproteins and fibrous proteins, which interferes with quantification.

Chemical ingredients and their rolesPolyacrylamide gel (PAG) had been known as a potential embedding medium for sectioning tissues as early as 1964.Two independent groups, Davis and Raymond, employed PAG in electrophoresis in 1959.[10] [11] It possessesseveral electrophoretically desirable features that make it a versatile medium. PAGE separates protein moleculesaccording to both size and charge. It is a synthetic gel, thermo-stable, transparent, strong, relatively chemically inert,can be prepared with a wide range of average pore sizes [12] . The pore size of a gel is determined by two factors, thetotal amount of acrylamide present (%T) (T = Total acrylamide-bisacrylamide monomer concentration) and theamount of cross-linker (%C) (C = Crosslinker concentration). Pore size decreases with increasing %T; withcross-linking, 5%C gives the smallest pore size. Any increase or decrease in %C increases the pore size, as pore sizewith respect to %C is a parabolic function with vertex as 5%C. This appears to be because of nonhomogeneousbundling of strands in the gel.This gel material can also withstand high voltage gradients, feasible for various staining and destaining procedures,and can be digested to extract separated fractions or dried for autoradiography and permanent recording. DISCelectrophoresis utilizes gels of different pore sizes. [13] [14] The name DISC was derived from the discontinuities inthe electrophoretic matrix and coincidentally from the discoid shape of the separated zones of ions. There are twolayers of gel, namely stacking or spacer gel, and resolving or separating gel.

SDS-PAGE 5

Transmission-Electron Microscopic image of a polyacrylamide gel.The pore size of a gel is determined by the total amount of monomer

present (%T) and the amount of cross-linker (%C).

Stacking gel

The stacking gel is a large pore PAG (4%T). This gel isprepared with Tris/HCl buffer pH 6.8 of about 2 pHunits lower than that of electrophoresis buffer(Tris/Glycine). These conditions provide anenvironment for Kohlrausch reactions determiningmolar conductivity, as a result, SDS-coated proteins areconcentrated to several fold and a thin starting zone ofthe order of 19 μm is achieved in a few minutes. Thisgel is cast over the resolving gel. The height of thestacking gel region is always maintained more thandouble the height and the volume of the sample to beapplied. This is based on isotachophoresis.

Chemical ingredients

• Tris (tris (hydroxy methyl) aminomethane)(C

4H

11NO

3; mW: 121.14). It has been used as a

buffer because it is an innocuous substance to mostproteins. Its pKa is 8.3 at 20 °C, making it a verysatisfactory buffer in the pH range from roughly 7 to9.

• Glycine (Amino Acetic Acid) (C2H

5NO

2; mW:

75.07). Glycine has been used as the source of trailing ion or slow ion because its pKa is 9.69 and mobility ofglycinate are such that the effective mobility can be set at a value below that of the slowest known proteins of netnegative charge in the pH range. The minimum pH of this range is approximately 8.0.

• Acrylamide (C3H

5NO; mW: 71.08). It is a white crystalline powder. While dissolving in water,

autopolymerization of acrylamide takes place. It is a slow spontaneous process by which acrylamide moleculesjoin together by head on tail fashion. But in presence of free radicals generating system, acrylamide monomersare activated into a free-radical state. These activated monomers polymerise quickly and form long chainpolymers. This kind of reaction is known as Vinyl addition polymerisation. A solution of these polymer chainsbecomes viscous but does not form a gel, because the chains simply slide over one another. Gel formationrequires hooking various chains together. Acrylamide is a neurotoxin. It is also essential to store acrylamide in acool dark and dry place to reduce autopolymerisation and hydrolysis.

• Bisacrylamide (N,N'-Methylenebisacrylamide) (C7H

10N

2O

2; mW: 154.17). Bisacrylamide is the most

frequently used cross linking agent for poly acrylamide gels. Chemically it is thought of having two-acrylamidemolecules coupled head to head at their non-reactive ends.

• Sodium Dodecyl Sulfate (SDS) (C12

H25

NaO4S; mW: 288.38). SDS is the most common dissociating agent

used to denature native proteins to individual polypeptides. When a protein mixture is heated to 100 °C inpresence of SDS, the detergent wraps around the polypeptide backbone. It binds to polypeptides in a constantweight ratio of 1.4 g/g of polypeptide. In this process, the intrinsic charges of polypeptides becomes negligiblewhen compared to the negative charges contributed by SDS. Thus polypeptides after treatment becomes a rod likestructure possessing a uniform charge density, that is same net negative charge per unit length. Mobilities of theseproteins will be a linear function of the logarithms of their molecular weights.

Without SDS, different proteins with similar molecular weights would migrate differently due to differences in mass charge ratio, as each protein has an isoelectric point and molecular weight particular to its primary

SDS-PAGE 6

structure. This is known as Native PAGE. Adding SDS solves this problem, as it binds to and unfolds theprotein, giving a near uniform negative charge along the length of the polypeptide.

• Ammonium persulfate (APS) (N2H8S2O8; mW: 228.2). APS is an initiator for gel formation.• TEMED (N, N, N', N'-tetramethylethylenediamine) (C6H16N2; mW: 116.21). Chemical polymerisation of

acrylamide gel is used for SDS-PAGE. It can be initiated by ammonium persulfate and the quaternary amine,N,N,N',N'-tetramethylethylenediamine (TEMED). The rate of polymerisation and the properties of the resultinggel depends on the concentration of APS and TEMED. Increasing the amount of APS and TEMED results in adecrease in the average polymer chain length, an increase in gel turbidity and a decrease in gel elasticity.Decreasing the amount of initiators shows the reverse effect. The lowest catalytic concentrations that will allowpolymerisation in the optimal period of time should be used. APS and TEMED are used, approximately inequimolar concentrations in the range of 1 to 10 mM.

Chemicals for processing and visualizationThe following chemicals are used for processing of the gel and the protein samples visualized in it:• Bromophenol blue (BPB) (3',3",5',5" tetrabromophenolsulfonphthalein) (C19H10Br4O5S; mW: 669.99). BPB

is the universal marker dye. Proteins and nucleic acids are mostly colourless. When they are subjected toelectrophoresis, it is important to stop the run before they run off the gel. BPB is the most commonly employedtracking dye, because it is viable in alkali and neutral pH, it is a small molecule, it is ionisable and it is negativelycharged above pH 4.6 and hence moves towards the anode. Being a small molecule it moves ahead of mostproteins and nucleic acids. As it reaches the anodic end of the electrophoresis medium electrophoresis is stopped.It can bind with proteins weakly and give blue colour.

• Glycerol (C3H8O3; mW: 92.09). It is a preservative and a weighing agent. Addition of glycerol (20-30 or 50%)is often recommended for the storage of enzymes. Glycerol maintains the protein solution at very lowtemperature, without freezing. It also helps to weigh down the sample into the wells without being spread whileloading.

• Coomassie Brilliant Blue R-250 (CBB)(C45H44N3NaO7S2; mW: 825.97). CBB is the most popular proteinstain. It is an anionic dye, which binds with proteins non-specifically. The structure of CBB is predominantlynon-polar. So is usually used (0.025%) in methanolic solution (40%) and acetic acid (7%). Proteins in the gel arefixed by acetic acid and simultaneously stained. The excess dye incorporated in the gel can be removed bydestaining with the same solution but without the dye. The proteins are detected as blue bands on a clearbackground. As SDS is also anionic, it may interfere with staining process. Therefore, large volume of stainingsolution is recommended, approximately ten times the volume of the gel.

• n-Butanol (C4H10O; mW: 74.12). Water saturated butanol is used as an overlay solution on the resolving gel.• Dithiothreitol (DTT; C4H10O2S2; mW: 154.25). DTT is a reducing agent used to disrupt disulfide bonds to

ensure the protein is fully denatured before loading on the gel; ensuring the protein runs uniformly. Traditionallythe toxic and less potent 2-mercaptoethanol was used.

Reducing SDS-PAGEBesides the addition of SDS, proteins may optionally be briefly heated to near boiling in the presence of a reducingagent, such as dithiothreitol (DTT) or traditionally 2-mercaptoethanol (beta-mercaptoethanol/BME), which furtherdenatures the proteins by reducing disulfide linkages, thus overcoming some forms of tertiary protein folding, andbreaking up quaternary protein structure (oligomeric subunits). This is known as reducing SDS-PAGE, and is mostcommonly used. Non-reducing SDS-PAGE (no boiling and no reducing agent) may be used when native structure isimportant in further analysis (e.g. enzyme activity, shown by the use of zymograms). For example, quantitativepreparative native continuous polyacrylamide gel electrophoresis (QPNC-PAGE) is a new method for separatingnative metalloproteins in complex biological matrices.

SDS-PAGE 7

Silver staining

Silver stained SDSPolyacrylamide gels

In the 14th century the silver staining technique was developed for colouring thesurface of glass. It has been used extensively for this purpose since the 16thcentury. The colour produced by the early silver stains ranged between light yellowand an orange-red. Camillo Golgi perfected the silver staining for the study of thenervous system. Golgi's method stains a limited number of cells at random in theirentirety.[15] The exact chemical mechanism by which this happens is still largelyunknown.[16] Silver staining was introduced by Kerenyi and Gallyas as a sensitiveprocedure to detect trace amounts of proteins in gels.[17] The technique has beenextended to the study of other biological macromolecules that have been separatedin a variety of supports.[18] Classical Coomassie Brilliant Blue staining can usuallydetect a 50 ng protein band, Silver staining increases the sensitivity typically 50times. Many variables can influence the colour intensity and every protein has itsown staining characteristics; clean glassware, pure reagents and water of highestpurity are the key points to successful staining.[19]

SDS-PAGE 8

Buffer systems

Postulated migration of proteins in a Laemmli gelsystem A: Stacking gel, B: Resolving gel, o:

sample application c: discontinuities in the bufferand electrophoretic matrix

Most protein separations are performed using a "discontinuous" buffersystem that significantly enhances the sharpness of the bands withinthe gel. During electrophoresis in a discontinuous gel system, an iongradient is formed in the early stage of electrophoresis that causes allof the proteins to focus into a single sharp band. This occurs in a regionof the gel that has larger pores so that the gel matrix does not retard themigration during the focusing or "stacking" event. Negative ions fromthe buffer in the tank then "outrun" the SDS-covered protein "stack"and eliminate the ion gradient so that the proteins subsequentlyseparate by the sieving action in the lower, "resolving" region of thegel.

Many people continue to use a tris-glycine or "Laemmli" bufferingsystem that stacks at a pH of 6.8 and resolves at a pH of ~8.3-9.0.These pHs promote disulfide bond formation between cysteineresidues in the proteins, especially when they are present at highconcentrations because the pKa of cysteine ranges from 8-9 andbecause reducing agent present in the loading buffer doesn't co-migratewith the proteins. Recent advances in buffering technology alleviatethis problem by resolving the proteins at a pH well below the pKa ofcysteine (e.g., bis-tris, pH 6.5) and include reducing agents (e.g.sodium bisulfite) that move into the gel ahead of the proteins tomaintain a reducing environment. An additional benefit of usingbuffers with lower pHs is that the acrylamide gel is more stable so the gels can be stored for long periods of timebefore use.[20] [21]

SDS gradient gel electrophoresis of proteins

Migration of proteins in SDS gels of varying acrylamide concentrations (%T). Themigration of nine proteins ranging from 94 kDa to 14.4 kDa is shown. Stacking

and unstacking occurs continuously in the gel, for every protein at a different gelconcentration. The dotted line indicates the discontinuity at the Gly¯/Cl¯ moving

boundary. Proteins between the fast leading electrolyte and the slow trailingelectrolyte are not diluted by diffusion.

As voltage is applied, the anions (andnegatively charged sample molecules)migrate toward the positive electrode(anode) in the lower chamber, the leadingion is Cl¯ ( high mobility and highconcentration); glycinate is the trailing ion(low mobility and low concentration).SDS-protein particles do not migrate freelyat the border between the Cl¯ of the gelbuffer and the Gly¯ of the cathode buffer.Friedrich Kohlrausch found that Ohm's lawalso applies to dissolved electrolytes.Because of the voltage drop between the Cl-and Glycine-buffers, proteins arecompressed (stacked) into micrometer thinlayers. [22] The boundary moves through a

SDS-PAGE 9

pore gradient and the protein stack gradually disperses due to an frictional resistance increase of the gel matrix.Stacking and unstacking occurs continuously in the gradient gel, for every protein at a different position. For acomplete protein unstacking the polyacrylamide-gel concentration must exceed 16% T. The two-gel system of"Laemmli" is a simple gradient gel. The pH discontinuity of the buffers is of no significance for the separationquality, and a "stacking-gel" with a different pH is not needed.

See also• Capillary electrophoresis• DNA electrophoresis• Eastern blotting• Electroblotting• Electrophoresis• Gel electrophoresis• History of electrophoresis• Isoelectric focusing• Isotachophoresis• Native Gel Electrophoresis• Northern blotting• Protein electrophoresis• Southern blotting• Two dimensional SDS-PAGE• Western blotting• Zymography

External links• Demystifying SDS-PAGE Video [23]

• Demystifying SDS-PAGE [24]

• SDS-PAGE Calculator [25] for customised recipes for TRIS Urea gels.• 2-Dimensional Protein Gelelectrophoresis [26]

• [27] Hempelmann E. SDS-Protein PAGE and Proteindetection by Silverstaining and Immunoblotting ofPlasmodium falciparum proteins. in: Moll K, Ljungström J, Perlmann H, Scherf A, Wahlgren M (eds) Methods inMalaria Research, 5th edition, 2008, 263-266

References[1] Shapiro AL, Viñuela E, Maizel JV Jr. (September 1967). "Molecular weight estimation of polypeptide chains by electrophoresis in

SDS-polyacrylamide gels.". Biochem Biophys Res Commun. 28 (5): 815–820. doi:10.1016/0006-291X(67)90391-9. PMID 4861258.[2] Weber K, Osborn M (August 1969). "The reliability of molecular weight determinations by dodecyl sulfate-polyacrylamide gel

electrophoresis.". J Biol Chem. 244 (16): 4406–4412. PMID 5806584.[3] Laemmli UK (August 1970). "Cleavage of structural proteins during the assembly of the head of bacteriophage T4". Nature 227 (5259):

680–685. doi:10.1038/227680a0. PMID 5432063.[4] Caprette, David. "SDS-PAGE" (http:/ / www. ruf. rice. edu/ ~bioslabs/ studies/ sds-page/ denature. html). . Retrieved 27 Sept 2009.[5] "What is the meaning of de -gas the acrylamide gel mix?" (http:/ / www. protocol-online. org/ biology-forums/ posts/ 17740. html). .

Retrieved 28 Sept 2009.[6] "SDS-PAGE" (http:/ / www. science. smith. edu/ departments/ Biochem/ Biochem_353/ sdspage. html). . Retrieved 12 Sept 2009.[7] Schägger, H; Von Jagow, G (1987). "Tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis for the separation of proteins in the

range from 1 to 100 kDa.". Anal. Biochem. 166 (2): 368–379. doi:10.1016/0003-2697(87)90587-2. PMID 2449095.[8] Andrews. "SDS-PAGE" (http:/ / www. dwalab. ca/ labman/ recipes/ PreparingtoRunTricineSDSGels. html). . Retrieved 27 Sept 2009.[9] http:/ / encorbio. com/ protocols/ SDS-Calc. htm

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[10] Davis BJ, Ornstein L (1959). "A new high resolution electrophoresis method.". Delivered at the Society for the Study of Blood at the NewYork Academy of Medicine.

[11] Raymond S, Weintraub L. (1959). "Acrylamide gel as a supporting medium for zone electrophoresis.". Science 130: 711.doi:10.1126/science.130.3377.711. PMID 14436634.

[12] Rüchel R, Steere RL, Erbe EF (1978). "Transmission-electron microscopic observations of freeze-etched polyacrylamide gels.". JChromatogr. 166: 563–575. doi:10.1016/S0021-9673(00)95641-3.

[13] Ornstein L (December 1964). "DISC ELECTROPHORESIS. I. BACKGROUND AND THEORY.". Ann N Y Acad Sci. 121: 321–349.doi:10.1111/j.1749-6632.1964.tb14207.x. PMID 14240533.

[14] Davis BJ (December 1964). "Disc Electrophoresis. 2, Method and application to human serum proteins". Ann. New York Acad. Sci 121:404–427. doi:10.1111/j.1749-6632.1964.tb14213.x. PMID 14240539.

[15] Grant G (Oct 2007). "How the 1906 Nobel Prize in Physiology or Medicine was shared between Golgi and Cajal". Brain Res Rev 55 (2):490–498. doi:10.1016/j.brainresrev.2006.11.004. PMID 17306375.

[16] Golgi C (1873). "Sulla struttura della sostanza grigia del cervello.". Gazzetta Medica Italiana (Lombardia) 33: 244–246.[17] Kerenyi L, Gallyas F (1973). "Über Probleme der quantitiven Auswertung der mit physikalischer Entwicklung versilberten

Agarelektrophoretogramme". Clin. Chim. Acta 47 (3): 425–436. doi:10.1016/0009-8981(73)90276-3. PMID 4744834.[18] Switzer RC 3rd, Merril CR, Shifrin S (Sep 1979). "A highly sensitive silver stain for detecting proteins and peptides in polyacrylamide

gels.". Anal Biochem. 98 (1): 231–237. doi:10.1016/0003-2697(79)90732-2. PMID 94518.[19] Hempelmann E, Schulze M, Götze O (1984). "Free SH-groups are important for the polychromatic staining of proteins with silver nitrat".

Neuhof V (ed)Electrophoresis '84 , Verlag Chemie Weinheim 1984: 328–330.[20] Schägger H, von Jagow G (1987). "Tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis for the separation of proteins in the

range from 1 to 100 kDa.". Anal Biochem. 166 (2): 368–379. doi:10.1016/0003-2697(87)90587-2. PMID 2449095.[21] Wiltfang J, Arold N, Neuhoff V (1991). "A new multiphasic buffer system for sodium dodecyl sulfate-polyacrylamide gel electrophoresis of

proteins and peptides with molecular masses 100,000-1000, and their detection with picomolar sensitivity.". Electrophoresis 12 (5): 352–366.doi:10.1002/elps.1150120507. PMID 1718736.

[22] Kohlrausch F (1897). "Ueber Concentrations-Verschiebungen durch Electrolyse im Inneren von Lösungen und Lösungsgemischen.".Ann.J.Phys.u.Chem. 62: 209–239. doi:10.1002/andp.18972981002.

[23] http:/ / sdspage. homestead. com/ TheVideo. html[24] http:/ / sdspage. homestead. com/[25] http:/ / www. omx-online. com/ calculator. html[26] http:/ / wwwzb. zb. kfa-juelich. de/ wiki/ index. php?title=Sample_preparation_2D[27] http:/ / www. biomalpar. org/ updatedMethods_In_Malaria_Research_5thedition. pdf

Article Sources and Contributors 11

Article Sources and ContributorsSDS-PAGE  Source: http://en.wikipedia.org/w/index.php?oldid=374655002  Contributors: Aa77zz, Aciel, Ahoerstemeier, Andrewrp, Arc de Ciel, Bender235, Benjicharlton, Bensaccount,Biochemza, BrewBelly, Brianoflee, Bryan Derksen, CZmarlin, Chaiken, Choanoflagellate, Closedmouth, CommonsDelinker, Cst17, Damnable123, David Munch, Discospinster, Dnapurifier,Eganio, Eykanal, Fabiform, GerryShaw, Gkrajeshrajesh, Graft, Graham87, Gustavocarra, Heathmoor, Hempelmann, Herbal Lemon, Hillarryous, Horst, I.D.10-t, J.delanoy, JOK, Jaganath,Japanese Searobin, Jepoirrier, Jimtassano, Julianonions, Justinm704, Jwfowble, Kierano, Kkmurray, Kupirijo, Lexor, Lightmouse, Likeitsmyjob, Lord Anubis, Lordmetroid, LostLucidity, MC10,Magnus Manske, Marshman, Mav, Mephistophelian, Michael Hardy, MichaelJanich, Nrusimhanathmisra, Orthank, PDH, Papercutbiology, Pdcook, Pharamund, Proteinwizard, Qchristensen,R'n'B, Ravi.patil30, Rjwilmsi, Roadnottaken, Robbrad3, RogueNinja, Rrburke, Rss100001, Sakkura, Seans Potato Business, Seonaidmargaret, Sfan00 IMG, SquidDNA, Sriram sh, Stephenb,Temporaluser, Terminator1000, Theone00, TimVickers, Tirkfl, Tregoweth, TutterMouse, UW, Wedian, Wintan29, Ww2censor, XApple, Xaosflux, Yasha, Yerpo, Zafiroblue05, 151 anonymousedits

Image Sources, Licenses and ContributorsImage:SDS-PAGE.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:SDS-PAGE.jpg  License: GNU Free Documentation License  Contributors: User Magnus Manske on en.wikipediaimage:SDS-PAGE sample.png  Source: http://en.wikipedia.org/w/index.php?title=File:SDS-PAGE_sample.png  License: Creative Commons Attribution 3.0  Contributors: User:Bensaccountimage:SDS-PAGE acrylamide stock.png  Source: http://en.wikipedia.org/w/index.php?title=File:SDS-PAGE_acrylamide_stock.png  License: Creative Commons Attribution 3.0  Contributors:User:Bensaccountimage:SDS-PAGE Acrylamide gel.png  Source: http://en.wikipedia.org/w/index.php?title=File:SDS-PAGE_Acrylamide_gel.png  License: Creative Commons Attribution 3.0  Contributors:User:Bensaccountimage:SDS-PAGE Buffers.png  Source: http://en.wikipedia.org/w/index.php?title=File:SDS-PAGE_Buffers.png  License: Creative Commons Attribution 3.0  Contributors: User:Bensaccountimage:SDS-PAGE Electrophoresis.png  Source: http://en.wikipedia.org/w/index.php?title=File:SDS-PAGE_Electrophoresis.png  License: Creative Commons Attribution 3.0  Contributors:User:BensaccountImage:Gel Blue Coomassie.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Gel_Blue_Coomassie.jpg  License: Creative Commons Attribution-Sharealike 2.0  Contributors: StephenHelms from Dallas, TX, United StatesImage:TEM image of a polyacrylamide gel.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:TEM_image_of_a_polyacrylamide_gel.jpg  License: Creative Commons Attribution 3.0 Contributors: User:TimVickersImage:Silver-stained SDS-PAGE gels before and after storage.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Silver-stained_SDS-PAGE_gels_before_and_after_storage.jpg License: Public Domain  Contributors: J.smith, TimVickersImage:Laemmli System.png  Source: http://en.wikipedia.org/w/index.php?title=File:Laemmli_System.png  License: Creative Commons Attribution 3.0  Contributors: Ernst HempelmannImage:Principle of high resolution SDS gel electrophoresis.png  Source: http://en.wikipedia.org/w/index.php?title=File:Principle_of_high_resolution_SDS_gel_electrophoresis.png  License:Creative Commons Attribution 3.0  Contributors: Ernst Hempelmann

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