Editing Protein secondary structure (section)

{{short description|General three-dimensional form of local segments of proteins}}
{{about|secondary structure in protein|the article about secondary structure in nucleic acid|Nucleic acid secondary structure}}
{{Protein structure}}
'''Protein secondary structure''' is the local spatial conformation of the [[polypeptide]] backbone excluding the side chains.<ref>{{cite journal | vauthors = Sun PD, Foster CE, Boyington JC | title = Overview of protein structural and functional folds | journal = Current Protocols in Protein Science | volume = 17 | issue = 1 | pages = Unit 17.1 | date = May 2004 | pmid = 18429251 | pmc = 7162418 | doi = 10.1002/0471140864.ps1701s35 }}</ref> The two most common [[Protein structure#Secondary structure|secondary structural elements]] are [[alpha helix|alpha helices]] and [[beta sheet]]s, though [[beta turn]]s and [[omega loop]]s occur as well. Secondary structure elements typically spontaneously form as an intermediate before the protein [[protein folding|folds]] into its three dimensional [[protein tertiary structure|tertiary structure]].

Secondary structure is formally defined by the pattern of [[hydrogen bond]]s between the [[Amine|amino]] hydrogen and [[carboxyl]] oxygen atoms in the peptide [[backbone chain|backbone]]. Secondary structure may alternatively be defined based on the regular pattern of backbone [[Dihedral angle#Dihedral angles of proteins|dihedral angle]]s in a particular region of the [[Ramachandran plot]] regardless of whether it has the correct hydrogen bonds.

The concept of secondary structure was first introduced by [[Kaj Ulrik Linderstrøm-Lang]] at [[Stanford]] in 1952.<ref>{{cite book | vauthors = Linderstrøm-Lang KU | title = Lane Medical Lectures: Proteins and Enzymes | year = 1952 | publisher = Stanford University Press | pages = 115 | asin = B0007J31SC}}</ref><ref name="pmid9144781">{{cite journal | vauthors = Schellman JA, Schellman CG | title = Kaj Ulrik Linderstrøm-Lang (1896–1959) | journal = Protein Sci. | volume = 6 | issue = 5 | pages = 1092–100 | year = 1997 | pmid = 9144781 | pmc = 2143695 | doi = 10.1002/pro.5560060516 | quote = He had already introduced the concepts of the primary, secondary, and tertiary structure of proteins in the third Lane Lecture (Linderstram-Lang, 1952) }}</ref> Other types of [[biopolymer]]s such as [[nucleic acid]]s also possess characteristic [[nucleic acid secondary structure|secondary structures]].