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Sodium Dodecyl Sulfate




Sodium dodecyl sulfate ('''SDS''' or NaDS) ( C H 3(CH2)11 O S O3 Na ) (FW 288.38), also known as '''sodium lauryl sulfate''' ( SLS ), is an Ion ic Surfactant that is used in household products such as Toothpaste s, Shampoo s, shaving foams and Bubble Bath s for its thickening effect and its ability to create a lather. The molecule has a tail of 12 carbon atoms, attached to a Sulfate group, giving the molecule the Amphiphilic properties required of a detergent.

It is prepared by sulphation of 1-dodecanol (lauryl alcohol, CH3(CH2)10CH2OH) followed by neutralisation with Sodium Carbonate . It is used in both industrially produced and home-made cosmetics.

Like all Detergent surfactants (including Soap s), it removes oils from the Skin , and can cause skin irritation. It is also irritating to the Eye s.

SDS can be converted by Ethoxylation to Sodium Laureth Sulfate (also called sodium lauryl ether sulfate; SLES), which is less harsh on the skin, probably because it is not as much of a protein denaturant as is the unethoxylated substance.

It is probably the most researched anionic surfactant compound.

In laboratories, SDS is commonly used in preparing Proteins for polyacrylamide Gel Electrophoresis ( SDS-PAGE ). SDS works by disrupting non-covalent bonds in the proteins, thereby denaturing them, causing the molecules to lose their native shape (conformation). Also, anions of SDS bind to the main Peptide chain at a ratio of one SDS anion for every two Amino Acid residues. This effectively imparts a negative charge on the protein that is proportional to the mass of that protein (about 1.4 g SDS/g protein). This new negative charge is significantly greater than the original charge of that protein. The Electrostatic Repulsion that is created by binding of SDS causes proteins to unfold into a rod-like shape thereby eliminating differences in shape as a factor for separation in the gel.

It has recently found application as a surfactant in Gas Hydrate or Methane Hydrate formation reactions, increasing the rate of formation as much as 700 times.


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