Talk:Polyacrylamide gel electrophoresis

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Molecular Biology: MCB

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Wiki Education Foundation-supported course assignment

This article is or was the subject of a Wiki Education Foundation-supported course assignment. Further details are available on the course page. Student editor(s): Emlau, NajDee18, Tinabrodnikova, Lorenavako, Vicky.mai36. Peer reviewers: Vicky.mai36.

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Difference with Western_blot

So isn't this exactly the same thing as a Western-blot ? Maybe the articles should be fused ? XApple 21:35, 25 February 2007 (UTC)[reply]

SDS-PAGE is one of the electrophoresis techniques that running to get the gel for western-blot, so that it can have a gel for protein transfer to the inert membrane for chemiluminscence detection. I think it is not appropiate to merge these 2 articles. meaningless 04:51, 27 February 2007 (UTC)[reply]

XApple, this is most definitely not the same thing as a western blot. It would not serve any purpose to merge that article with this one. Biochemza 22:57, 22 September 2007 (UTC)[reply]

Why SDS is used

SDS is used for two reasons, first it denatures the protein (with the exclusion of disulfide links) such that the secondary, teriary, and quatranry stuctures are not a factor. Secondly, since proteins can have a positive, negative, or neutral charge SDS (which is a negatively charged detergent) standardizes the protein. Hope that helps! -- Robert Stone, Jr. 00:15, 1 January 2007 (UTC)[reply]

I think it will help if we give a basic idea of the frictional coefficient. The laws of electrostatics state that the electrical force, F electric, on an ion with charge q in an electric field of strengh E is expressed by:

                     F_electric = qE

The resulting electrophoretic migration of the ion through the solution is opposed by a frictional force

                     F_friction = vf

where v is the rate of migration (velocity) of the ion and f is its frictional coefficient. The frictional coefficient is a measure of the drag that the solution exerts on the moving ion and is dependent on the size, shape, and state of solvation of the ion as well as on the viscosity of the solution. In a constant electric field, the forces on the ion balance each other:

                           qE = vf

so that each ion moves with a constant characteristic velocity. An ion´s electrophoretic mobility, µ, is defined

                                   v   q
                               µ = - = -
                                   E   f

Ref: BIOCHEMISTRY Donald and Judith G. Voet, second edition, WILEY, pg 89. 1995

native PAGE

some info on native PAGE would be nice 202.36.134.22 04:03, 31 October 2007 (UTC)[reply]

Kohlrausch reactions

The phrase Kohlrausch reactions appears in the article, however, it links to the biography of the namesake. The biography does not go into detail of what this reaction is. I suggest creating a new article entitle Kohlrausch reactions or some expansion on the biography. LostLucidity (talk) 00:26, 25 January 2008 (UTC)[reply]

Kohlrausch found that Ohm’s law also applies to dissolved electrolytes. Kohlrausch F (1897). "Ueber Concentrations-Verschiebungen durch Electrolyse im Inneren von Lösungen und Lösungsgemischen.". Ann.J.Phys.u.Chem. 62: 209-239. Ernst Hempelmann (talk) 14 July 2008

Smile

Something on the way in which gels 'smile' and why might be nice in this article? —Preceding unsigned comment added by 82.211.95.178 (talk) 14:55, 26 February 2008 (UTC)[reply]

Sometimes outer lanes in the gel show a distinct curvature toward the outer edges.This is caused by non-uniform gel distribution.We overcome some of the smiling problems by by pouring the gel at many different positions into the cuvette and by enhanced cooling for even temperature distribution across all sample lanes (running the gel in the coldroom). Ernst Hempelmann (talk) 18.July 2008

Which samples can be used?

Is it true, that only proteins can be separated with this technique? Why not any molecule? —Preceding unsigned comment added by 130.225.22.254 (talk) 14:15, 22 March 2009 (UTC)[reply]

Theoretically, all mixtures containing anions can be sampled. Yet, the gel has relatively huge pores for the huge protein molecules. The gel is not suitable for separating smaller anions. Furthermore, electricity is applied to the cell, meaning simpler anions will probably just be broken down through electrolysis. Lastly, detection is often visual which involves sticking coloured or fluorescent dyes to the proteins. It is highly unlikely substances like coomassie brilliant blue will colour just any random anion! Be my guest to look anything mentioned up. Redtails (talk) 16:32, 18 June 2009 (UTC)[reply]

What determines the properties of the gel?

The text says "The rate of polymerisation and the properties of the resulting gel depends on the concentration of APS and TEMED."

In the German Wikipedia, it is stated that the properties of the gel depend on the relative concentration of acrylamide and bisacrylamide, and as far as I know, this is correct. Maybe someone could confirm that and add it to the english text. —Preceding unsigned comment added by 62.178.237.94 (talk) 08:23, 22 April 2009 (UTC)[reply]

Both are correct: the rate of polymerisation and the properties of the resulting gel depends on the concentration of APS and TEMED and the pore size of a gel is determined by the total amount of monomer present (%T) and the amount of cross-linker (%C).Ernst Hempelmann (talk) 23 April 2009

Issue with intro paragraph

SDS PAGE requires that proteins to be run are denatured to thier primary structures and coated with the SDS detergent so that charges and native folding are not factors, only primary structure length which is directly related to weight. I would like to contest the statement in the intro paragraph that states that the proteins mobility in a PAGE gel is a function of "high order protein folding". This is incorrect for the reason stated above. Prudhommei1 (talk) 19:04, 24 September 2009 (UTC)[reply]

Perhaps "higher order folding" meant primary structure/protein length. Anyways it is confusing so I will remove it. You can edit the article yourself btw. Bensaccount (talk) 19:38, 24 September 2009 (UTC)[reply]

Protocol oddities

While the Procedure section as it stand now looks very professional, I do have some nits to pick, since there are some odd (in my experience) things in there. I've done Westerns in half a dozen different labs (and thus used half a dozen different protocols), but there are two things I've never heard before. (1)Degassing the gel solution, and (2) the use of different buffers for anode and kathode. Where do these come from? Just wondering, as both seem totally unnecessary to me. Also, I would add to the first section the heating of the sample to >90 degrees C to aid denaturing, in my experience universally done. 82.21.156.156 (talk) 20:25, 27 September 2009 (UTC)[reply]

Good questions.

Regarding the different buffers, I will add some links to protocols that do this. [1] [2] The best reference I could find as to why there are different anode/cathode buffers is: [3] which says it affects the speed & resolution.

Degassing is done to help evenly polymerize the gel. [4]

I added the heater. Bensaccount (talk) 00:34, 28 September 2009 (UTC)[reply]

First figure

The figure caption on the first gel on the page says "Picture of an SDS-PAGE. The molecular marker is in the left lane". The molecular marker page linked talks only about DNA markers. Since this is an SDS-PAGE gel it should be a protein ladder. — Preceding unsigned comment added by 137.186.174.29 (talk) 04:26, 10 July 2011 (UTC)[reply]

Removed link Hempelmann (talk) 06:08, 20 July 2011 (UTC)[reply]

ignores most variants

This article is pretty much only about Laemmli-type discontinuous SDS-PAGE, and mostly ignores all other types of SDS-PAGE (different buffer systems, non-discontiuous, Schaegger-type, etc.) Although disc. SDS-PAGE is probably the most used, it is not the only variant. Currently the article gives the impression that SDS-PAGE is synonymous with Laemmli gels. I will try to address that, but further input is very welcome. Thanks, Rainbowwrasse (talk) 12:51, 13 October 2011 (UTC)[reply]

lousy

I have PhD in molecular biology and run SDS PAGE gels for a living I don't edit wiki cause I don't like the idea that work i do for free can be used by for profits, and cause i'm tired of re re re correcting stupidity whoever is responsible for this page take out all those stupid graphics showing weighing out chemicals learn something about SDS page, and update the refs etc good luck (eg, coomassie may still be the most popular stain, but it is now often used in non organic (aq) solutions, not with methanol; the ivgn fluor dyes are catching up; — Preceding unsigned comment added by 50.195.10.169 (talk) 15:19, 29 November 2012 (UTC)[reply]

As you are an expect why are you reading the article if you you do not intend to contribute to it? For those readers who have never used the method, or seen it demonstrated, the graphics are useful. What aspects of SDS PAGE do you think are missing and need to be learned about? Graham Colm (talk) 19:15, 29 November 2012 (UTC)[reply]

Article scope expanded

I've edited this article to expand its scope to include all types of polyacrylamide gel electrophoresis and not just SDS-PAGE, since there is so much overlap between all these methods. See discussion at Talk:Gel electrophoresis#Unmerging Agarose Gel Electrophoresis?. Antony–22 (^talk⁄_contribs) 01:55, 27 June 2013 (UTC)[reply]

SDS-PAGE

I think there is a need for a separate page for SDS-PAGE, mainly because that is the most performed of the PAGE. This page can be a general introduction for the PAGE, theories, and forms of PAGE, use of PAGE for DNA electrophoresis (e.g. in DNA sequencing), etc. Hzh (talk) 11:38, 1 October 2013 (UTC)[reply]