sentence: Secondary structure refers to highly regular local sub-structures.
sentences_after: Two main types of secondary structure, the alpha helix and the beta strand, were suggested in 1951 by Linus Pauling and coworkers. These secondary structures are defined by patterns of hydrogen bonds between the main-chain peptide groups.
concept_name: secondary structure
headings: Protein structure Levels of protein structure Secondary structure
categories: Molecular biology Proteins