The layers beta are secondary structures which are observed in portions of proteins . (cf Structure of the proteins)
A layer beta is the sum of several bits beta (chains of amino-acids laid out in accordion) connected by Hydrogen bond (weak connections).

There exist 2 types of provision of layers beta: antiparallel layers beta and parallel layers beta.

The pathogenicity of the prion (protein responsible for the Disease of Creutzfeldt-Jacob) is due to the transformation of a Hélice alpha into layer beta.