SDS-PAGE Sodium Dodecyl Sulfate - Polyacrylamid Gel Electrophoresis

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SDS-PAGESodium Dodecyl Sulfate - Polyacrylamid
Gel Electrophoresis

• Timothy G. Standish, Ph. D.

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Sodium Dodecyl Sulfate

• 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

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SDSSodium Dodecyl Sulfate
C12H25NaO4S

• 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

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SDS and Proteins
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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

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Polyacrylamide Gels

• Polyacrilamide is a polymer made of acrylamide
  (C3H5NO) and bis-acrilamide (N,N-methylene-bis-ac
  rylamide C7H10N2O2)

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Polyacrylamide Gels

• Acrylamide polymerizes in the presence of free
  radicals typically supplied by ammonium persulfate

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Polyacrylamide Gels

• Acrylamide polymerizes in the presence of free
  radicals typically supplied by ammonium persulfate

• TMED (N,N,N,N-tetramethylethylenediamine)
  serves as a catalyst in the reaction

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Polyacrylamide Gels

• bis-Acrylamide polymerizes along with acrylamide
  forming cross-links between acrylamide chains

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Polyacrylamide Gels

• bis-Acrylamide polymerizes along with acrylamide
  forming cross-links between acrylamide chains

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Polyacrylamide Gels

• Pore size in gels can be varied by varying the
  ratio of acrylamide to bis-acrylamide

• Protein separations typically use a 291 or
  37.51 acrylamide to bis ratio

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SDS-PAGE
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