Editing Protein (section)

=== Polypeptides ===

[[File:Peptide bond.jpg|thumb|polypeptide]]

The understanding of proteins as [[polypeptide]]s, or chains of amino acids, came through the work of [[Franz Hofmeister]] and [[Hermann Emil Fischer]] in 1902.<ref>{{cite web|url=http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/hofmeister-franz|title=Hofmeister, Franz|publisher=encyclopedia.com|access-date=4 April 2017|archive-url=https://web.archive.org/web/20170405073423/http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/hofmeister-franz|archive-date=5 April 2017|url-status=live}}</ref><ref>{{cite web | vauthors = Koshland DE, Haurowitz F |url=https://www.britannica.com/science/protein/Conformation-of-proteins-in-interfaces#ref593795|title=Protein, section: Classification of protein|publisher=britannica.com|access-date=4 April 2017|archive-url=https://web.archive.org/web/20170404225132/https://www.britannica.com/science/protein/Conformation-of-proteins-in-interfaces#ref593795|archive-date=4 April 2017|url-status=live}}</ref> The central role of proteins as [[enzyme]]s in living organisms that catalyzed reactions was not fully appreciated until 1926, when [[James B. Sumner]] showed that the enzyme [[urease]] was in fact a protein.<ref name="Sumner1926" />

[[Linus Pauling]] is credited with the successful prediction of regular protein [[secondary structure]]s based on [[hydrogen bonding]], an idea first put forth by [[William Astbury]] in 1933.<ref name="Pauling1951" /> Later work by [[Walter Kauzmann]] on [[Denaturation (biochemistry)|denaturation]],<ref name="Kauzmann1956" /><ref name="Kauzmann1959" /> based partly on previous studies by [[Kaj Ulrik Linderstrøm-Lang|Kaj Linderstrøm-Lang]],<ref name="Kalman1955" /> contributed an understanding of [[protein folding]] and structure mediated by [[hydrophobic core|hydrophobic interactions]].<ref>{{Cite journal |last=Dill |first=Ken A. |date=1990 |title=Dominant forces in protein folding |url=https://pubs.acs.org/doi/abs/10.1021/bi00483a001 |journal=Biochemistry |volume=29 |issue=31 |pages=7133–7155 |doi=10.1021/bi00483a001|pmid=2207096 }}</ref>

The first protein to have its amino acid chain [[protein sequencing|sequenced]] was [[insulin]], by [[Frederick Sanger]], in 1949. Sanger correctly determined the amino acid sequence of insulin, thus conclusively demonstrating that proteins consisted of linear polymers of amino acids rather than branched chains, [[colloid]]s, or [[cyclol]]s.<ref name=Sanger1949/> He won the Nobel Prize for this achievement in 1958.<ref name="Lecture 1958"/> [[Christian Anfinsen]]'s studies of the [[oxidative folding]] process of ribonuclease A, for which he won the nobel prize in 1972, solidified the [[thermodynamic hypothesis]] of protein folding, according to which the folded form of a protein represents its [[Free energy (thermodynamics)|free energy]] minimum.<ref name="pmid17754377">{{cite journal |vauthors=Richards FM |year=1972 |title=The 1972 nobel prize for chemistry |journal=Science |volume=178 |issue=4060 |pages=492–3 |bibcode=1972Sci...178..492R |doi=10.1126/science.178.4060.492 |pmid=17754377}}</ref><ref name="marshall">{{Cite journal |last1=Marshall |first1=G. R. |last2=Feng |first2=J. A. |last3=Kuster |first3=D. J. |year=2008 |title=Back to the future: Ribonuclease A |journal=Biopolymers |volume=90 |issue=3 |pages=259–77 |doi=10.1002/bip.20845 |pmid=17868092 |doi-access=free}}</ref>