Bioinformatics, Protocols, DNA RNA Protein Proteomics
home > sds-page-gel-electrophoresis > index.php
home > sds-page-gel-electrophoresis > index.php
 |
|---|
You have to register before you can post on our forums or use our advanced features. Register Now! Its Free and Fast!
Already registered? Login now below.
Already registered and Forgot your password? Click below to recover it.
Join now - it's fast and free!
Molecular Station is THE largest network of researchers, scientists and science lovers anywhere!
If it's green or wriggles, it's biology. If it stinks, it's chemistry. If it doesn't work, it's physics. ~Handy Guide to Science
Written and updated March 2008 by Moleculardude. Copyright 2007/2008.
Definition: SDS-PAGE is an abbreviation for sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis.
SDS-PAGE is a molecular biology technique used to separate proteins accordingly by size. SDS-PAGE also can separate DNA and RNA molecules.
In what is probably the most powerful technique for resolving protein mixtures, proteins are exposed to ionic detergent SDS (sodium dodecylsulfate) before and during gel electrophoresis. SDS denatures proteins, causing multimric proteins to dissociate into their subunits, and all polypeptide chains are forced into extended conformations with similar charge:mass ratios. SDS treatment therefore eliminates the effects of differences in shape so that chain length, which reflects mass, is the sole determinant of the migration rate of proteins in SDS- polyacrylamide electrophoresis.
Even chains that differ in molecular weight by less than 10 percent can be separated by this technique. Moreover, the molecular weight of a protein can be determined by comparison to a protein ladder or molecular weight ladder which is run on the same gel.
(see Figure 1)
Figure 1. This acrylamide gel is used to separate proteins. The colored spots are standard-size markers, which are prestained. This is usually used to make a western blot. The proteins are transfered to a membrane and then detected with an antibody to a specific protein.
SDS-PAGE, sodium dodecyl sulfate polyacrylamide gel electrophoresis, is a technique used in biochemistry, genetics and molecular biology to separate proteins according to their electrophoretic mobility (a function of length of polypeptide chain or molecular weight as well as higher order protein folding, posttranslational modifications and other factors).
The solution of proteins to be analyzed is first mixed with SDS, an anionic detergent which denatures secondary and non–disulfide–linked tertiary structures, and applies a negative charge to each protein in proportion to its mass. 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 structure. This is known as Native PAGE. Adding SDS solves this problem, as it binds to and unfolds the protein, giving a near uniform negative charge along the length of the polypeptide.
SDS bind in a ratio of approximately 1.4 g SDS per 1.0 g protein (although binding ratios can vary from 1.1-2.2 g SDS/g protein), giving an approximately uniform mass:charge ratio for most proteins, so that the distance of migration through the gel can be assumed to be directly related to only the size of the protein. A tracking dye may be added to the protein solution to allow the experimenter to track the progress of the protein solution through the gel during the electrophoretic run.
Electrophoresis is a technique for separating, or resolving molecules in a mixture under the influence of an applied electric field, also called electrophoretic mobility.. Dissolved molecules in an electric field move, or migrate at a speed determined by their charge:mass ratio. For example if two have the same mass and shape, the one with the greater net charge will move faster toward an electrode. The separation of small molecules, such as amino acids and nucleotides, is one of the many uses of electrophoresis. In this case, a small drop of sample is deposited on a strip of filter paper or other porous substrate, which is soaked with a conducting solution. When an electric field is applied as the ends of the strip, small molecules dissolved in the conducting solution move along the strip at a rate corresponding to their magnitude of their charge.
Because many proteins or nucleic acids that differ in size and shape have nearly identical charge:mass ratios, electrophoresis of these macromolecules in solution results in little or no separation of molecules of different lengths. However, successful separation of proteins and nucleic acids can be accomplished by electrophoresis in various gels (semisolid suspensions in water) rather than in a liquid solution. Electrophoretic separation of proteins is most commonly performed in polyacrylamide gels. These gels are cast between a pair of glass plates by polymerizing a solution of acrylamide monomers into polyacrylamidechains and simultaneously cross-linking the chains into a semisolid matrix. The pore size of a gel can be varied by adjusting the concentration of polyacrylamide and the crosslinking reagent.
When a mixture of proteins is applied to a gel and an electric current applied, smaller proteins migrate faster than larger proteins through the gel. The rate of movement is influenced by the gel’s pore size and the strength of the electric field. The pores in a highly cross-linked polyacrylamide gel are quite small. Such a gel could resolve small proteins and peptides, but large proteins would not be able to move through it.
As mentioned, the proteins are mixed with SDS an anionic detergent which binds to the proteins and denatures their secondary and non–disulfide–linked tertiary structure with the addition of heat. SDS also applies a uniform negative electrical charge to each protein in proportion to its mass.
If SDS was not used in separation, proteins with similar molecular weights would migrate differently in the gel due to differences in their mass to charge ratios. As proteins are separated using electrical current and pore size of the gel matrix, differences in charges (in addition to mass) would play a role in separation.
A tracking dye may be added to the protein solution to allow the experimenter to track the progress of the protein solution through the gel during the electrophoretic run.
Immidiate dissappearing of bands on DNA sequencing gels after silver staining
Hi
One of my friend is facing a problem with silver staining of sequencing gels in which the DNA sample bands along with the bands of marker are...
Two Closely Migrating Bands on SDS-PAGE Gel
Hello. I do not now why but I see two close migrating bands on gel sds-page. why two bands very close? Usually i no get two bands, usually one band...
SDS Boiling of Samples Any Alternative Methods?
i hate boiling my samples as i get aggregates of proteins running near the top of the gels. also if you are using specific dyes/probes etc you want...
I rewet the membrane in methanol...is Ab gone?
On an overnight exposure trying to detect a low abundance protein, my membrane dried out around the edges so I rewet it in methanol...is my Ab no...
SDS PAGE Protein Concentration Estimation
Please help this person :
I have a problem with my SDS PAGE. I estimate protein concentration by BCA method.I use two dilutions of the protein for...
Separating Similar Sized Proteins on SDS-PAGE?
Hi,
as SDS-PAGE separates proteins based on size how can one separate proteins which are the same size?
:cussing:
thanks
You must REGISTER NOW to post a question in the SDS-PAGE Gel Electrophoresis Forum. Login now if you have already registered.
Demystifying SDS-Page Video
An instructional video aimed at teaching the process of SDS-PAGE to college students with basic biochemical understandings. www.sdspage.net From Youtube user mattbrewbaker.
Added by: kiki06
Tags: sds-page gel electrophoresis
Date: 2008-04-28
SDS-PAGE Gel Electrophoresis Video
SDS-PAGE Gel Electrophoresis Sodium dodecylsulphate gelelectrophoresis from Youtube user pr6655321
Added by: kiki06
Tags: sds-page gel electrophoresis protocol method
Date: 2008-04-28
Removing Stacking Gel SDS-PAGE Video
Removing Stacking Gel SDS-PAGE
Added by: kiki06
Tags: sds-page gel electrophoresis stacking removing
Date: 2008-04-28
Pouring Resolving SDS-PAGE Gel Video
A video on pouring the resolving gel for SDS-PAGE. From the Youtube user be115.
Added by: timjum
Tags: sds-page gel electrophoresis resolving pouring protoocl method
Date: 2008-04-28
SDS-PAGE Resolving Gel SDS Video
SDS-PAGE Resolving Gel SDS. Adding SDS on top of the resolving gel. From Youtube user be115.
Added by: timjum
Tags: sds-page gel electrophoresis resolving protocol method
Date: 2008-04-28
Assembling SDS-PAGE Mini Gels Protean 3 Video
A video showing the steps for assembling the Protean 3 minigel. From youtube user be115.
Added by: timjum
Tags: assembly gel sds-page protean minigel
Date: 2008-04-28
SDS-PAGE Gel Electrophoresis Time Lapse Video
SDS-PAGE Gel Electrophoresis Time Lapse. Running an sds-page gel over time.
Added by: timjum
Tags: sds-page gel electrophoresis running
Date: 2008-04-28
Loading SDS-PAGE Gel Video
Loading SDS-PAGE Gel
Added by: oBWhat
Tags: loading sds-page gel electrophoresis sample
Date: 2008-04-28
Assembling SDS-PAGE Electrophoresis Plates Video
Assembling SDS-PAGE Electrophoresis Plates. From youtube user be115.
Added by: oBWhat
Tags: sds-page gel electrophoresis protocol method plates assembly assembling
Date: 2008-04-28
Running an SDS-PAGE Gel Video
Running an SDS-PAGE GelFrom Youtube user be115.
Added by: kiki06
Tags: sds-page gel electrophoresis protocol method
Date: 2008-04-27
Disclaimer / Terms of Service |
Privacy Policy|
©2005-2007 Molecular Station.com, All rights reserved.
![[أربيك]](http://www.molecularstation.com/translate/images/flag_ar.gif){kind=small}
Send this page to a friend
