Editing Glycoprotein (section)

== Synthesis ==
The glycosylation of proteins has an array of different applications from influencing cell to cell communication to changing the thermal stability and the folding of proteins.<ref name="Lehninger_2013" /><ref name="Davis_2002">{{cite journal |vauthors=Davis BG |title=Synthesis of glycoproteins |journal=Chemical Reviews |volume=102 |issue=2 |pages=579–602 |date=February 2002 |pmid=11841255 |doi=10.1021/cr0004310}}</ref> Due to the unique abilities of glycoproteins, they can be used in many therapies.<ref name="Davis_2002" /> By understanding glycoproteins and their synthesis, they can be made to treat cancer, [[Crohn's disease|Crohn's Disease]], high cholesterol, and more.<ref name="Picanco_e_Castro_2018" />

The process of glycosylation (binding a carbohydrate to a protein) is a [[post-translational modification]], meaning it happens after the production of the protein.<ref name="Picanco_e_Castro_2018" /> Glycosylation is a process that roughly half of all human proteins undergo and heavily influences the properties and functions of the protein.<ref name="Picanco_e_Castro_2018" /> Within the cell, glycosylation occurs in the [[endoplasmic reticulum]].<ref name="Picanco_e_Castro_2018" />

=== Recombination ===
[[File:Variety of glycans.svg|thumb|337x337px|Depiction of differences in glycans amongst different animals.]]
There are several techniques for the assembly of glycoproteins. One technique utilizes [[Recombinant DNA|recombination]].<ref name="Picanco_e_Castro_2018" /> The first consideration for this method is the choice of host, as there are many different factors that can influence the success of glycoprotein recombination such as cost, the host environment, the efficacy of the process, and other considerations.<ref name="Picanco_e_Castro_2018" /> Some examples of host cells include E. coli, yeast, plant cells, insect cells, and mammalian cells.<ref name="Picanco_e_Castro_2018" /> Of these options, mammalian cells are the most common because their use does not face the same challenges that other host cells do such as different glycan structures, shorter half life, and potential unwanted immune responses in humans.<ref name="Picanco_e_Castro_2018" /> Of mammalian cells, the most common cell line used for recombinant glycoprotein production is the [[Chinese hamster ovary cell|Chinese hamster ovary]] line.<ref name="Picanco_e_Castro_2018" /> However, as technologies develop, the most promising cell lines for recombinant glycoprotein production are human cell lines.<ref name="Picanco_e_Castro_2018" />

=== Glycosylation ===
The formation of the link between the glycan and the protein is key element of the synthesis of glycoproteins.<ref name="Gamblin_2009" /> The most common method of glycosylation of N-linked glycoproteins is through the reaction between a protected glycan and a protected Asparagine.<ref name="Gamblin_2009" /> Similarly, an O-linked glycoprotein can be formed through the addition of a [[glycosyl]] donor with a protected [[Serine]] or [[Threonine]].<ref name="Gamblin_2009" /> These two methods are examples of natural linkage.<ref name="Gamblin_2009" /> However, there are also methods of unnatural linkages.<ref name="Gamblin_2009" /> Some methods include ligation and a reaction between a serine-derived sulfamidate and thiohexoses in water.<ref name="Gamblin_2009" /> Once this linkage is complete, the amino acid sequence can be expanded upon using solid-phase peptide synthesis.<ref name="Gamblin_2009" />