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Collagen triple helix
Mass / length primary structure 3 x 200-1000 amino acids
Secondary to quaternary structure Triple helix
Precursor Procollagen polypeptide chains and procollagen
Isoforms 28 in humans
Drug information
ATC code B02 BC07 , G04 BX11 , D11 AX57
Drug class Fiber protein
Parent taxon Tissue animals

Collagens (precursor tropocollagens ; internationalized spelling collagens ; stress on the penultimate syllable) are a group of structural proteins (a “ protein ” forming a fiber bundle ) mainly of the connective tissue (more precisely: the extracellular matrix ) that occur only in multicellular animals (including humans ). Collagens are found in the white, inelastic fibers of tendons, ligaments, bones and cartilage, among other things. Layers of the skin (subcutaneous tissue) also consist of collagens.


Close up
Human skin.jpg
Human skin
Rhinoceros skin

In the human body, collagen is the most common protein with over 30% of the total mass of all proteins . It is an essential organic component of connective tissue ( bones , teeth , cartilage , tendons , ligaments ) and the skin . Collagen (from the Greek: glue producing ) originally got its name from its earlier use as bone glue in woodworking. It is the main raw material for making gelatin .

Collagen consists of individual, long collagen molecules ( protein chains ) that form a left-handed helix (similar to the polyproline II helix ). Three of these helices are arranged in a right-hand superhelix. The triple helix is stabilized by hydrogen bonds between the individual strands.

What is striking about the primary structure (amino acid sequence) of collagen is that every third amino acid is glycine . A sequence motif that is frequently repeated in the collagen protein family is glycine- proline - hydroxyproline .

Collagen fibers have enormous tensile strength and are hardly stretchable. The tight winding is decisive for the high tensile strength of collagen fibers.

Collagens play a crucial role in the biomineralization of vertebrates .

In common parlance, type I collagen is equated with “collagen”. In terms of quantity, type I collagen is the most important collagen in mammals and, due to its use as gelatine, it is also the best known. However, there are other types of collagen that differ structurally from type I collagen and that perform other important biological functions. Gelatine is the denatured form of fibrillary collagen type I, II and / or III and is mostly obtained from slaughterhouse waste. It should be noted here that type II collagen occurs primarily in cartilage ; mixtures of type I and III collagen come from tendons , ligaments and the skin .


Functional genes of collagen structural proteins can be found in all phyla of multicellular animals, in sponges , cnidarians and mammals, mainly in their extracellular matrix and in the connective tissue. Collagens do not occur in other organisms such as fungi, plants or protozoa.


Collagen molecule

The polypeptide chains of collagen are individually synthesized by the ribosomes of the rough endoplasmic reticulum . Only triple helical molecules of the extracellular matrix (ECM) are called collagen molecules or tropocollagen . They have in common that they are made up of three polypeptide chains. These are each in left-handed collagen helices (α-chains, not to be confused with right-handed α-helices ) and are wound together in the form of the characteristic right-handed triple helix. Each individual collagen helix can be composed of 600 to 3000 amino acids, depending on the type of collagen, and is equipped with large domains made up of repetitive GXY sequences.

Thus there is a glycine ( G ) residue at every third position . Glycine as the smallest amino acid fits perfectly into the triple helix with its very tight turns. The amino acid proline is often found in position X. Due to its rigid ring structure, proline acts here as a “corner” in the polypeptide chain and supports the formation of tight turns within the triple helix. 4- Hydroxyproline is mainly located at position Y and stabilizes the triple helix via hydrogen bonds between neighboring polypeptide chains. The use of glycine, proline and hydroxyproline limits the rotation of the polypeptide chain and takes into account the tight spatial conditions within the triple helix.

Structure level molecular domain
Primary structure (= sequence) Polypeptide chains with repetitive GXY sequences
Secondary structure left-handed collagen helices (α chains)
Tertiary structure right-handed triple helix made of 3 polypeptide chains (tropocollagen Ø1.5 nm)
Quaternary structure Microfibrils Ø20–40 nm, fibrils Ø300–500 nm, fibers Ø4–12 μm

The presence of hydroxylysine next to hydroxyproline is also characteristic of collagen. Hydroxylysine forms the prerequisite for the formation of covalent cross-links, with which the individual triple helices can be spatially fixed within the collagen fibrils.

Collagen fibrils

Electron micrograph of collagen fibers.

In the fibrils, neighboring collagen molecules are not arranged flush, but around 67 nm, i.e. H. offset by about a fifth of their length. The consequence of this arrangement is that transverse stripes can be seen on electron microscope images of metal-contrasted collagen fibrils. A characteristic banding pattern is created, which is repeated every 67 nm (234 amino acids) and is referred to as the D period. This divides the α chains into four homologous regions D1-D4. The bands appearing in a D unit are denoted by a – e. The collagen fibrils are ordered polymers that can be many micrometers long in mature tissue. They are often grouped into larger, cable-like bundles, the collagen fibers. In tendons, the collagen type I fibril diameter is 50–500 nm, in the skin 40–100 nm and in the cornea (cornea of ​​the eye) 25 nm. The fibrillogenesis of collagen is often regulated by small leucine-rich proteoglycans , so that in the corresponding tissues Fibrils with a defined diameter and a defined arrangement can arise.

Structure elucidation

Today's picture of the collagen triple helix and the spatial arrangement of the amino acid residues and their hydrogen bonds among each other is largely based on the X-ray crystallographic work of the Indian scientists G. N. Ramachandran and Gopinath Kartha (1954).

The former Max Planck Institute for Protein and Leather Research in Munich (founded in 1956 to clarify the connective tissue through sponsorship of the leather industry ) provided essential clarification (the entire primary structure of type I collagen as well as the macrostructures of types IV and VI) under the Head of Klaus Kühn (after the institute was relocated to the Max Planck Institute for Biochemistry in Martinsried).


Collagen is mainly in fibroblasts , chondroblasts , osteoblasts and odontoblasts made but collagen is also used in many other cell types synthesized . The biosynthesis of collagen in fibroblasts has been studied best. Fibroblasts have an extensive, rough endoplasmic reticulum and a well-developed Golgi apparatus in order to be able to participate in the secretion of collagens into the extracellular matrix. Fibroblasts produce collagen de novo and secrete it into the extracellular matrix. In addition, fibroblasts are able to break down collagen with the help of enzymes called collagenases .

1. Transcription : So far 42 genes are known that are involved in the biosynthesis of collagen and code for 28 different types of collagen. Each gene codes for a specific mRNA sequence and the gene name typically contains COL as a prefix. The synthesis is started by the activation of certain genes that are responsible for the formation of certain α-peptides. These are mainly the α-peptides α1, α2 or α3.

2. Translation : As soon as the mRNA reaches the cytoplasm from the cell nucleus, the mRNA combines with the ribosomal subunits for translation to form prepro-α chains (also called prepropeptide). These prepro-α chains contain a signal sequence at the N terminus. This signal sequence is recognized by a signal recognition particle on the rough endoplasmic reticulum so that the chain can get into the lumen of the rough ER.

3. Prepro-α-chain to procollagen : Three modifications of the prepro-α-chain are necessary to form an α-chain. This is followed by the triple helix formation of three α-chains to form procollagen.

  1. Cleavage of the signal sequence : The signal sequence at the N -terminus of the prepro-α-chain by signal peptidases split off and there is a pro-α chain, with the N - and C -terminal propeptides is provided.
  2. Hydroxylation : In the endoplasmic reticulum, OH groups are attached to individual proline and lysine residues of polypeptide chains that have already formed or that have already formed ( hydroxylation ). Ascorbic acid (vitamin C) is an important cofactor in the hydroxylation of the amino acids proline to hydroxyproline by the enzyme prolyl-4-hydroxylase ( EC ) and lysine to hydroxylysine by the enzyme lysyl hydroxylase ( EC ). Hydroxyproline has the function of strengthening the triple helix within a collagen molecule via hydrogen bonds between neighboring collagen polypeptide chains. Hydroxylysine is used to anchor covalent cross-links between collagen molecules. If there is no hydroxylation, only damaged collagen molecules are formed that cannot fulfill their function as structural proteins. It should be noted here that almost all symptoms of the ascorbic acid deficiency disease scurvy can be traced back to the faulty biosynthesis of collagen.
  3. Glycosylation : Finally, some lysine residues are usually glycosylated by procollagen galactosyltransferase ( EC ) or procollagen glucosyltransferase ( EC ) or other glycosylation enzymes . A collagen α chain was synthesized.
  4. Triple helix formation : The triple helix formation is initiated by the formation of disulfide bonds between the C -terminal propeptides with the aid of a protein disulfide isomerase ( EC ). Three α-chains form a three-stranded helix molecule, the procollagen , via hydrogen bonds .

4. Procollagen secretion and transport to the Golgi apparatus : Because of the size of procollagen molecules (approx. 300 nm), they do not fit into the normal COPII vesicles (50–90 nm) of the endoplasmic reticulum. To enable transport, a copy of the ubiquitin protein is bound by the enzyme CUL3 – KLHL12 to SEC31 of the protein complex SEC13 – SEC31, so that the size of the transport vesicles can be modified. In addition, the transmembrane protein TANGO1 participates in the coordination of procollagen secretion. After the procollagen has been packaged in the modified transport vesicles, it can be transported to the Golgi apparatus .

5. Modification in the Golgi apparatus : The last post-translational modification to the procollagen takes place in the Golgi apparatus by adding and modifying oligosaccharides. Which enzymes are responsible for the modification of N -terminus-bound oligosaccharides depends on the location of the post-translational modification in the Golgi apparatus. The enzymes for the respective areas of the Golgi apparatus are tabulated below:

Area of ​​the Golgi apparatus enzyme
cis α-mannosidase I.
medial N -acetylglucosaminyl transferase I
medial α-mannosidase II
medial N -acetylglucosaminyl transferase II
medial Fucosyl transferase
trans Galactosyl transferase
trans Sialyltransferase

6. Transport from the Golgi apparatus to the plasma membrane and subsequent exocytosis into the extracellular matrix : The secretory vesicles that constrict on the trans side of the trans Golgi network are called Golgi to plasma membrane carriers (GPC). In the GPC, the procollagen is transported to the plasma membrane, more precisely to the protrusions of the plasma membrane, so-called fibripositors . The triple-helical collagen molecules are released from the cell. The release of the molecules into the extracellular space takes place by exocytosis with the basis of the fibripositors, in which the glycosyl components seem to be involved.

7. Formation of the tropocollagen : Immediately after being released from the cell, the propeptides are split off with the help of procollagen peptidases . The enzyme procollagen- N -endopeptidase ( EC ) is necessary for the cleavage of amino-terminal sequences, while the enzyme procollagen- C -endopeptidase ( EC ) cleaves carboxy-terminal procollagen sequences. The tropocollagen is formed .

8. Fibrillogenesis : After splitting off the procollagen peptides, individual tropocollagen molecules assemble to form collagen fibrils (fibrillogenesis). Other molecules can attach themselves to the fibrils and thus adapt the fibril diameter. These include the so-called small leucine-rich repeat proteoglycans (SLRPs), including, for example, decorin , fibromodulin and lumican belong.

Cross-linking of two collagen triple helices by aldol condensation of neighboring allysine residues, which were formed extracellularly by lysyl oxidase ( EC ).

9. Cross-linking : After individual triple-helical tropocollagen molecules are offset by a fifth of their length, covalent cross-linking takes place via nearby hydroxylysine residues that have to be converted , whereby the spatial arrangement is permanently fixed. The hydroxylysine residues (created intracellularly by the lysyl hydroxylase) are oxidized to allysine by the lysyl oxidase ( EC ). The two neighboring allysine residues enter into an aldol condensation , which means that this neighborhood is fixed by permanent cross-linking. Cross-linked collagen fibrils are formed.

10. Formation of collagen fibers : Many such covalently stabilized collagen fibrils ultimately form collagen fibers, which represent the basic structure of the extracellular matrix of all tissue animals .

Collagen types

The collagens are divided into several subgroups. 28 different types of collagen are known (types I to XXVIII) as well as at least ten other proteins with collagen-like domains. The members of the collagen family known to date are listed below.

Type description Gene (s) Diseases
I. In mammals, type I collagen, a fibrillary collagen, is the most common type of collagen and occurs in skin, tendons, fascia, bones, vessels, internal organs and dentin. COL1A1 , COL1A2 Osteogenesis imperfecta types I – IV, Ehlers-Danlos syndrome (classic, arthrochalasia), infantile cortical hyperostosis
II fibrillar; Structural protein of hyaline and elastic cartilage ; 50% of all proteins in cartilage consist of type II collagen; Part of the vitreous COL2A1 Hypochondrogenesis , achondrogenesis type II , Stickler syndrome , congenital spondyloepiphyseal dysplasia , Spondyloepimetaphyseal dysplasia Strudwick type , Kniest dysplasia
III fibrillar; Part of the granulation tissue and reticular fibers ; also part of the vessel walls, internal organs, skin, uterus and cornea COL3A1 Acrogeria , Ehlers-Danlos syndrome (vascular)
IV Part of the basal lamina and the lens of the eye ; Also serves as part of the filtration system in capillaries and glomeruli of the nephron COL4A1 , COL4A2 , COL4A3 , COL4A4 , COL4A5 , COL4A6 Alport syndrome , Goodpasture syndrome , thin basement membrane type nephropathy
V fibrillar; Part of the interstitium , placental tissue and the dermoepidermal junction zone; mostly associated with intermediate tissues containing type I collagen COL5A1 , COL5A2 , COL5A3 Ehlers-Danlos syndrome (classic, hypermobile)
VI Organization of various components in the extracellular matrix ; Maintaining the integrity of the various tissues; mostly associated with tissues containing type I collagen COL6A1 , COL6A2 , COL6A3 , COL6A5 Ullrich type congenital muscular dystrophy , Bethlem myopathy , atopic eczema
VII forms anchor fibrils in the dermoepidermal junction zone COL7A1 Dystrophic epidermolysis bullosa , beard syndrome
VIII short chain; integral part of the subendothelial layer of connective tissue cells in blood vessels and the Descemet membrane of the cornea; Migration and proliferation of smooth muscle cells in the tunica media of the blood vessels COL8A1 , COL8A2 Posterior corneal polymorphic dystrophy , Fuchs endothelial dystrophy 1
IX FACIT 1 ; Part of the hyaline cartilage and vitreous body; mostly associated with tissues containing collagen type II and XI COL9A1 , COL9A2 , COL9A3 Multiple epiphyseal dysplasia (types 2,3 and 6)
X short chain; Part of chondrocytes in the hypertrophic zone COL10A1 Metaphyseal chondrodysplasia type Schmid , spondylometaphyseal dysplasia type Sutcliffe
XI fibrillar; Part of the cartilage COL11A1 , COL11A2 Stickler syndrome type 2, Marshall syndrome , Weissenbacher-Zweymüller phenotype , oto-spondylo-megaepiphyseal dysplasia
XII FACIT, interaction with type I collagen fibrils, decorin and glycosaminoglycans COL12A1 Bethlem myopathy 2, Ullrich type congenital muscular dystrophy 2
XIII MACIT 2 ; interacts with integrin α 1 β 1 , fibronectin and other components of the basement membrane such as Nidogen-2 and Perlecan ; is involved in the cell-matrix connection and in cell adhesion; Linking the muscle fiber with the basement membrane COL13A1 Congenital myasthenic syndrome type 19
XIV FACIT; also known as undulin; plays a role in the adhesive integration of collagen fascicles ; is present in the basement membrane during embryonic development COL14A1 -
XV Multiplexin; is able to connect the basement membrane with the loose connective tissue ; stabilizes microvessels and muscle cells in the heart and skeletal muscle ; can inhibit angiogenesis COL15A1 -
XVI FACIT; involved in cell adhesion and inducing integrin- mediated cellular responses such as proliferation ; promotes the life of intestinal sub epithelial myofibroblasts (engl. intestinal subepithelial myofibroblasts , ISEMF) in the intestinal wall COL16A1 -
XVII MACIT; plays an important role in the integrity of hemidesmosomes and in the attachment of keratinocytes to the underlying basement membrane; promotes the invasion of extravillous trophoblasts during placenta development COL17A1 Bullous pemphigoid , epidermolysis bullosa junctionalis
XVIII Multiplexin; Maintenance of retinal structure and closure of the neural tube ; a cleavage product of collagen XVIII is endostatin with a molecular mass of 20  kDa COL18A1 Knobloch syndrome type 1
XIX FACIT; is mostly located in the vascular , neuronal , mesenchymal and epithelial basement membrane; Cross-bridge between fibrils and other extracellular matrix molecules COL19A1 -
XX FACIT; is mostly found in the epithelial layer of the cornea, the embryonic skin, the sword process and in the tendon COL20A1 -
XXI FACIT; is an extracellular matrix component of the blood vessel wall that is secreted by smooth muscle cells COL21A1 -
XXII FACIT; participates in cell adhesion of ligands in multilayered epithelia and in fibroblasts COL22A1 -
XXIII MACIT; resides in the epidermis and other epithelia such as the tongue, intestines, lungs, brain, kidney, and cornea; interacts with integrin α 2 β 1 COL23A1 -
XXIV mainly expressed in bone tissue COL24A1 -
XXV MACIT; joins amyloid fibrils with protease- resistant aggregates and can bind heparin COL25A1 -
XXVI is often the formation of nasal polyps in the nasal cavity associated COL26A1 -
XXVII is located in the basement membrane of keratinocytes in hemidesmosomes type I, which is substantially as adhesion and surface receptor in stratified epithelia acts COL27A1 -
XXVIII located mainly in the sciatic nerve and on the basement membrane of some Schwann cells ; integral part of the Ranvier ring and surrounds non- myelinated glial cells COL28A1 -
1FACIT: F ibril A ssociated C ollagens with I nterrupted T riple helices
2Macit: M embrane A ssociated C ollagens with I nterrupted T riple helices

Structure of type I collagen

In the case of collagen type I, the three collagen polypeptide chains are the α-chains, [α1 (I) 2 α2 (I)], which wind around one another to form a triple helix. The type I collagen α1 chain gene consists of 50 exons , over half of which are 54 base pairs (bp) in length or two to three times that length. They code for the sequence (GXY) 6 or a multiple thereof.


Collagen is mainly used in the form of gelatine , which is obtained from the split of beef , pork skin and bones of cattle and pigs.

Nutrition and feed

In Germany, around 32,000 t of edible quality gelatine are produced annually, the total European production is 120,000 t (70% pork rind, 18% bones, 10% beef split, 2% other). Around 90,000 tonnes are used in Germany, two thirds of which are in the food sector and around half of the remainder is in the animal feed sector.

In addition, collagen is used for the production of artificial casings that serve as sausage casings .


Around 15,000 t are processed in the chemical and pharmaceutical industries. The main areas of application in the pharmaceutical industry are tablets and vitamin preparations (hard and soft capsules) as well as gelatine suppositories. Gelatine is also used for hemostatic sponges and as a blood plasma substitute.

Collagen is also used in regenerative medicine as a nutrient medium in tissue engineering . This can be used, for example, to produce skin replacement materials for severe burns.


Collagen has also been used in cosmetics for many years, where it is primarily intended to reduce skin aging, or to promote anti-aging . Today, collagen products are used in cosmetics in the form of creams. The collagen used for this is usually extracted from pig skin. Collagen is the most important structural protein in the skin and fulfills a variety of functions to maintain its elasticity and flexibility.

Collagen is sometimes injected into the skin as a wrinkle injection to treat wrinkles, wrinkles, and other skin problems .


In analog photography, gelatine forms the basis for the photosensitive layers on film and photo paper. Even modern printer papers for printing color images are coated with gelatine.


Cross-linked collagen fibers form the structure of leather and give it its tensile strength. With the help of tanning agents, certain properties such as flexibility and resistance to decomposition by microorganisms are achieved.

See also

A sculpture by Julian Voss-Andreae in San Francisco (California, USA). The structure of the 3.40 m high stainless steel sculpture ("unraveling collagen") is based on crystallographic data of the collagen molecule.


  • Shirley Ayad, Ray P. Boot-Hanford, Martin J. Humphries, Karl E. Kadler, C. Adrian Shuttleworth: The Extracellular Matrix FactsBook. 2nd edition. Academic Press (Harcourt Brace & Company), San Diego CA et al. 1998, ISBN 0-12-068911-1 , p. 43 ff.
  • Jürgen Brinckmann, Holger Notbohm, Peter K. Müller (Eds.): Collages. Primer in Structure, Processing and Assembly (= Topics in Current Chemistry . Vol. 247). Springer, Berlin et al. 2005, ISBN 3-540-23272-9 .

Web links

Commons : collages  - album with pictures, videos and audio files
Wiktionary: collages  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ^ Hermann Ehrlich: Chitin and collagen as universal and alternative templates in biomineralization . In: International Geology Review . tape 52 , no. 7-8 , April 30, 2010, pp. 661-699 , doi : 10.1080 / 00206811003679521 (English).
  2. Aaron L. Fidler et al: A unique covalent bond in basement membrane is a primordial innovation for tissue evolution. In: Proceedings of the National Academy of Sciences. Volume 111, No. 1, 2014, pp. 331-336. doi: 10.1073 / pnas.1318499111 .
  3. Jason W. Holland et al.: A novel minicollagen gene links cnidarians and myxozoans. In: Proceedings of the Royal Society B: Biological Sciences. Volume 278, No. 1705, 2011, pp. 546-553. doi: 10.1098 / rspb.2010.1301 .
  4. ^ Richard P. Tucker, Josephine C. Adams: Adhesion networks of cnidarians: A postgenomic view. In: Kwang W. Jeon (Ed.): International Review of Cell and Molecular Biology . Academic Press. Volume 308, Chapter 8, Jan. 7, 2014, pp. 323-377. doi: 10.1016 / B978-0-12-800097-7.00008-7 .
  5. Klaus Kühn : Structure and biochemistry of collagen. In: Chemistry in Our Time . Volume 8, 1974, pp. 97-103. doi: 10.1002 / ciuz.19740080402 .
  6. ^ Gregory D. Cramer, Susan A. Darby: Basic and Clinical Anatomy of the Spine, Spinal Cord . Elsevier Health Sciences, 2005, ISBN 978-0-323-07142-0 , pp. 580 ( limited preview in Google Book search).
  7. Collagens. In: ScienceDirect. Retrieved October 13, 2019 .
  8. ^ Hao Wang, Branko Stefanovic: Role of LARP6 and Nonmuscle Myosin in Partitioning of Collagen mRNAs to the ER Membrane. In: PLoS One . 9 (10) 2014, PMID 25271881 , doi : 10.1371 / journal.pone.0108870 .
  9. U. Lindert, M. Gnoli, M. Maioli, MF Bedeschi, L. Sangiorgi, M. Rohrbach, C. Giunta: Insight into the Pathology of a COL1A1 Signal Peptide Heterozygous Mutation Leading to Severe Osteogenesis Imperfecta. In: Calcified Tissue International . 102 (3) March 2018, pp. 373–379, doi : 10.1007 / s00223-017-0359-z .
  10. J. Myllyharju: Prolyl 4-hydroxylases, the key enzymes of collagen biosynthesis. In: Matrix Biology. Volume 22, Number 1, March 2003, pp. 15-24, PMID 12714038 (Review).
  11. Sakari Kellokumpu, Raija Sormunen, Jari Heikkinen, Raili Myllylä: Lysyl Hydroxylase, a Collagen Processing Enzyme, Exemplifies a Novel Class of Luminallyloriented Peripheral Membrane Proteins in the Endoplasmic Reticulum . In: The Journal of Biological Chemistry . 269 ​​(148) December 2, 1994, pp. 30524-30529, (PDF).
  12. Richard Harwood, Michael E. Grant, David S. Jackson: Studies on the glycosylation of hydroxylysine residues during collagen biosynthesis and the subcellular localization of collagen galactosyltransferase and collagen glucosyltransferase in tendon and cartilage cells. In: Biochemical Journal. 152, 1975, p. 291, doi : 10.1042 / bj1520291 .
  13. ^ David J. Stephens: Collagen secretion explained. In: Nature. 482, 2012, p. 474, doi : 10.1038 / 482474a .
  14. ^ R. Kornfeld, S. Kornfeld: Assembly of Asparagine-Linked Oligosaccharides. In: Annual Review of Biochemistry. 54, 1985, p. 631, doi : 10.1146 / .
  15. EG Canty: Procollagen trafficking, processing and fibrillogenesis. In: Journal of Cell Science. 118, 2005, p. 1341, doi : 10.1242 / jcs.01731 .
  16. ^ Charles M. Lapière, Albert Lenaers, Leonard D. Kohn: Procollagen peptidase: An enzyme excising the coordination peptides of procollagen . In: Proc Natl Acad Sci US A. Volume 68 , no. December 12 , 1971, p. 3054-3058 , PMC 389589 (free full text).
  17. A. Oldberg, P. Antonsson, K. Lindblom, D. Heinegård: A collagen-binding 59-kd protein (fibromodulin) is structurally related to the small interstitial proteoglycans PG-S1 and PG-S2 (decorin). In: The EMBO Journal . Volume 8, Number 9, September 1989, pp. 2601-2604, PMID 2531085 , PMC 401265 (free full text).
  18. JA Rada, PK Cornuet, JR Hassell: Regulation of corneal collagen fibrillogenesis in vitro by corneal proteoglycan (lumican and decorin) core proteins. In: Experimental eye research. Volume 56, Number 6, June 1993, pp. 635-648, doi : 10.1006 / exer.1993.1081 , PMID 8595806 .
  19. C. Söderhäll, I. Marenholz, T. Kerscher, F Rüschendorf, F. Rüschendorf, J. Esparza-Gordillo, G Mayr, M Albrecht: Variants in a Novel Epidermal Collagen Gene (COL29A1) Are Associated with Atopic Dermatitis . In: PLoS Biology . 5, No. 9, 2007, p. E242. doi : 10.1371 / journal.pbio.0050242 . PMID 17850181 . PMC 1971127 (free full text).
  20. K. Rappold: Gelatine - A natural food. bmi aktuell 1/2004, publisher. Information center for baking agents and baking ingredients for the production of bread and fine baked goods e. V.
  21. a b gelatin . Gelatine Manufacturers of Europe , accessed May 23, 2013.
  22. a b Oliver Türk: Material use of renewable raw materials . 1st edition. Springer Vieweg, Wiesbaden 2014, ISBN 978-3-8348-1763-1 , p. 111-115 .
  23. ^ PDB Community Focus: Julian Voss-Andreae, Protein Sculptor . In: Protein Data Bank Newsletter . No. 32 (winter), 2007 ( PDF ).
  24. Barbara Ward: 'Unraveling Collagen' structure to be installed in Orange Memorial Park Sculpture Garden . In: Expert Rev. Proteomics . tape 3 , no. 2 , April 2006, p. 174 , doi : 10.1586 / 14789450.3.2.169 .