Editing Silk (section)

===Chemical properties===
Silk emitted by the silkworm consists of two main proteins, [[sericin]] and [[fibroin]], fibroin being the structural center of the silk, and sericin being the sticky material surrounding it. Fibroin is made up of the [[amino acid]]s [[glycine|Gly]]-[[serine|Ser]]-Gly-[[alanine|Ala]]-Gly-Ala and forms [[beta sheet|beta pleated sheet]]s. [[Hydrogen bond]]s form between chains, and side chains are oriented above and below the plane of the hydrogen bond network.

The high proportion (50%) of glycine allows tight packing. This is because glycine has no side chain and is therefore unencumbered by steric strain. The addition of alanine and serine makes the fibres strong and resistant to breaking. This tensile strength is due to the many interceded hydrogen bonds, and when stretched the force is applied to these numerous bonds and they do not break.

Silk resists most [[mineral acid]]s, except for [[sulfuric acid]], which dissolves it. It is yellowed by perspiration. [[Chlorine bleach]] will also destroy silk fabrics.