Why does SDS make proteins separate purely by size in electrophoresis?
Because it swamps their differences. Proteins vary in shape and net charge, so they cannot be separated by size alone in their native state. SDS unfolds them and binds along the chain at roughly 1.4 grams per gram of protein, giving every protein a uniform negative charge proportional to its length and a similar rod-like shape. Mobility then depends only on molecular weight.
2
What is SDS used for in emulsion polymerisation?
It stabilises the growing polymer particles. In emulsion polymerisation, monomer droplets and forming latex particles must be kept dispersed in water and prevented from coalescing, and SDS adsorbs onto their surfaces and provides the electrostatic repulsion that keeps them apart. Its low cost and reliability make it a standard choice.
3
Is SDS the same as sodium lauryl sulfate?
Yes, both names refer to CAS 151-21-3. SDS is the name used in biochemistry, sodium lauryl sulfate in cosmetics and detergents. Commercial SLS is often a mixture of chain lengths derived from coconut or palm kernel alcohol, whereas analytical grade SDS is specified to a high dodecyl content, so the grade matters even though the name is the same.
4
Why is SDS used as the reference irritant in dermatology?
Because it produces a reliable, reproducible irritant reaction at a known concentration, which makes it the standard positive control in patch testing and in skin irritation studies. That property follows from its efficiency at denaturing skin proteins, which is the same mechanism that makes it an aggressive cleaner.
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