Collagen

The triple helix: three left-handed polyproline type II helices (red, green, blue) assemble by an axial hydrogen bond to form a right-handed triple helix, the tertiary structure of collagen.

Collagen (/ˈkɒlədʒən/) is the main structural protein in the extracellular matrix of the connective tissues of many animals. It is the most abundant protein in mammals,^[1] making up 25% to 35% of protein content. Amino acids are bound together to form a triple helix of elongated fibril^[2] known as a collagen helix. It is mostly found in cartilage, bones, tendons, ligaments, and skin. Vitamin C is vital for collagen synthesis.

Depending on the degree of mineralization, collagen tissues may be rigid (bone) or compliant (tendon) or have a gradient from rigid to compliant (cartilage). Collagen is also abundant in corneas, blood vessels, the gut, intervertebral discs, and the dentin in teeth.^[3] In muscle tissue, it serves as a major component of the endomysium. Collagen constitutes 1% to 2% of muscle tissue and 6% by weight of skeletal muscle.^[4] The fibroblast is the most common cell creating collagen in animals. Gelatin, which is used in food and industry, is collagen that was irreversibly hydrolyzed using heat, basic solutions, or weak acids.^[5]

^ Shoulders MD, Raines RT (2009). "Collagen structure and stability". Annual Review of Biochemistry. 78: 929–958. doi:10.1146/annurev.biochem.77.032207.120833. PMC 2846778. PMID 19344236.
^ "Leather grown using biotechnology is about to hit the catwalk". The Economist. 26 August 2017. Archived from the original on 1 September 2017. Retrieved 2 September 2017.
^ Britannica Concise Encyclopedia 2007
^ Sikorski ZE (2001). Chemical and Functional Properties of Food Proteins. Boca Raton, Florida: CRC Press. p. 242. ISBN 978-1-56676-960-0.
^ Bogue RH (1923). "Conditions Affecting the Hydrolysis of Collagen to Gelatin". Industrial and Engineering Chemistry. 15 (11): 1154–59. doi:10.1021/ie50167a018.

[1] Shoulders MD, Raines RT (2009). "Collagen structure and stability". Annual Review of Biochemistry. 78: 929–958. doi:10.1146/annurev.biochem.77.032207.120833. PMC 2846778. PMID 19344236.

[2] "Leather grown using biotechnology is about to hit the catwalk". The Economist. 26 August 2017. Archived from the original on 1 September 2017. Retrieved 2 September 2017.

[3] Britannica Concise Encyclopedia 2007

[4] Sikorski ZE (2001). Chemical and Functional Properties of Food Proteins. Boca Raton, Florida: CRC Press. p. 242. ISBN 978-1-56676-960-0.

[5] Bogue RH (1923). "Conditions Affecting the Hydrolysis of Collagen to Gelatin". Industrial and Engineering Chemistry. 15 (11): 1154–59. doi:10.1021/ie50167a018.

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