SDS-PAGE is a widely used electrophoresis technique to separate and identify proteins and nucleic acids based on their molecular weight. It employs sodium dodecyl sulfate to denature proteins, allowing for their separation in a gel under an electric field, where smaller proteins migrate faster than larger ones. The method can quantify proteins, determine molecular weight, and assess sample purity using various staining techniques.

1. SDS- Polyacrylamide Gel Electrophoresis

2.  Standard test that used to determine the charged
molecules, mainly proteins and nucleic acids.
 widely used in biochemistry ,forensics, genetics and
molecular biology to separate and identify proteins
according to their molecular weight.
 This method separates proteins based primarily on
their molecular weights.
 Laemmli system of SDS-PAGE was first introduced
in 1970s.

3.  Separates protein in an electric field.
 Migrate through a liquid or semisolid medium
when subjected to an electric field from anode
to cathode terminal.
 Molecules flow at different rates depend on
the molecular size of proteins.

4. -the proteins samples are having uniformed structure and charge
 the separation will depend on their molecular weight only.
-SDS-treated proteins have very similar charge-to-mass ratios, and similar shapes.
During PAGE, the rate of migration of SDS-treated proteins is effectively
determined by molecular weight.
-Small proteins migrate faster through the gel under the influence of the applied
electric field, whereas large proteins are successively retarded, due to the sieving
effect of the gels.

5.  SDS –page coated large proteins migrate slowly
through the gel matrix and small proteins migrate
quickly through the matrix.
 The nearer the band to the well.The large the
molecular size of protein.

6.  Negatively charged detergent sodium dodecyl
sulfate.
 Used to denature and linearize the proteins
 Coated the proteins with negatively charged.

7.  SDS-PAGE is differentiated into two systems.
*continuous sds-page
*discontinuous sds-page.
• Polyacrylamide is used to form a gel, a matrix of a
pores which allow the molecules migrate at
different rates.

8.  The size of pores is determined by the
concentration of acrylamide.
 The higher the concentration, the smaller the
size of pores.
 Discontinuos sds-page consist of two
different gels.
 *stacking gel -4%of acrylamide
 *separating gel-range from 5-15% of
acrylamide.

9. Preparation of gel
 Clean the plates and combs.
 Set up the plates on the rack.
 Pour the separating gel.
 Pour the stacking gel.
 Gel storage.

11.  Visualizes the band under UV light.
 Types of stains;
1. Coomassie Blue;
* Coomassie Brilliant Blue staining The Coomassie dyes R-250 and G-250 bind to
proteins stoichiometrically through their sulfonic acid groups.
* . The interactions between dye and protein are Van der Waals and ionic. The sulfonic
acid groups interact with positive amine groups. Therefore coomassie dye binds to
wide range of proteins.
* Limited to ~100ng of protein.
1. Silver stain;
*most sensitive test
*detection limit 0.1-1.0ng of protein

13.  Determine purity of protein samples
 Determine molecular weight of protein
 Identifying disulfide bonds between protein
 Quantifying proteins
 Blotting applications

14.  SDS-page is a technique that used to separate
proteins according to their molecular size
through the gel.
 Proteins are unfolded and migrate from cathode
to anode terminal at different rates.
 Molecular weight is determined by compare the
result with a standard curve of relative motility of
standard proteins.

15. • P.K .Gupta molecular biology second
edition.
• https://www.google.co.in/search?q=sds+page
+principle.

16. Thank you