SDS-PAGE（Sodium Dodecyl Sulfate - Polyacrylamid Gel Electrophoresis）

SDS is a common ingredient in detergents
Other names for SDS include laurel sulfate and sodium laurel sulfate
As a detergent SDS destroys protein secondary, tertiary and quaternary structure
This makes proteins rod shaped
SDS also sticks to proteins in a ratio of approximately 1.4 g of SDS for each gram of protein
Negative charge on the sulfate groups of SDS mask any charge on the protein

SDS

Sodium Dodecyl Sulfate
Because it is amphipathic, SDS is a potent detergent
SDS may also be called sodium lauryl sulfate and is a common ingredient of shampoos laundry detergent and other cleaning products

SDS and Proteins

SDS nonpolar chains arrange themselves on proteins and destroy secondary tertiary and quarternary structrure
Thus shape is no longer an issue as the protein SDS complex becomes rod shaped

In aqueous solutions, SDS polarizes releasing Na+ and retaining a negative charge on the sulfate head
So much SDS binds to proteins that the negative charge on the SDS drowns out any net charge on protein side chains
In the presence of SDS all proteins have uniform shape and charge per unit length

Polyacrylamide Gels
Polyacrilamide is a polymer made of acrylamide (C ₃ H ₅ NO) and bis-acrilamide (N,N’-methylene-bis-acrylamide C ₇ H ₁₀ N ₂ O ₂ )