Collagen

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Collagen is the main structural protein in the extracellular space in various connective tissues of the animal body. As a major component of connective tissue, it is the most abundant protein in mammals, which make up from 25% to 35% of all body protein content. Collagen consists of amino acids that are wound together to form triple helices to form an elongated fibril. It is mostly found in fibrous tissues such as tendons, ligaments and skin.

Depending on the level of mineralization, collagen tissue may be stiff (bone), compliant (tendon), or have a gradient from rigid to compliant (cartilage). It is also abundant in the corneas, blood vessels, intestines, intervertebral discs, and dentine in the teeth. In muscle tissue, it serves as a major component of endomysium. Collagen is one to two percent of the muscle tissue, and accounts for 6% of the weight of the strong tendon muscles. Fibroblasts are the most common cells that create collagen. Gelatin, which is used in food and industry, is collagen that has been hydrolyzed irreversibly. Collagen also has many medical uses in treating bone and skin complications.

The name collagen comes from the Greek ????? ( kÃÆ'³lla ), which means "glue", and suffix ->, -gen , which indicates "generates". This refers to the early use of compounds in the process of boiling the skin and the tendons of horses and other animals to gain glue.

Video Collagen

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Collagen occurs in many places throughout the body. More than 90% of collagen in the human body, however, is type I.

So far, 28 types of collagen have been identified and described. They can be divided into several groups according to the structure they form:

• Fibrillar (Type I, II, III, V, XI)
• Without fibrillar
  • FACIT (Fibril Associated Collagens with Interrupted Triple Helices) (Type IX, XII, XIV, XIX, XXI)
  • Short chain (Type VIII, X)
  • Basal membrane (Type IV)
  • Multiplexin (Multiple Triple Helix domains with Interruptions) (Type XV, XVIII)
  • MACIT (Membrane Associated Collagens with Interrupted Triple Helices) (Type XIII, XVII)
  • More (Type VI, VII)

The five most common types are:

• Type I: skin, tendon, blood vessels, organs, bones (major component of bone organic part)
• Type II: cartilage (the main collagen component of the cartilage)
• Type III: reticulates (the main component of reticular fibers), commonly found with type I.
• Type IV: forming the basal lamina, the basement membrane layer secreted by the epithelium.
• Type V: cell, hair and placenta surface

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Medical use

Heart applications

The collagen heart frame that includes four heart valve rings, is histologically, elastic and uniquely attached to the heart muscle. The cardiac framework also includes septa separate from the heart chamber - the interventricular septum and the atrioventricular septum. The contribution of collagen to cardiac measures of performance briefly represents the strength of the continuous torque opposite to the mechanics of the blood pressure fluid emitted from the heart. The collagen structure that divides the upper space of the heart from the lower chamber is an impermeable membrane that excludes blood and electrical impulses through a typical physiological means. With the support of collagen, atrial fibrillation should not deteriorate into ventricular fibrillation. Collagen-coated density varies with cardiac muscle mass. Mass, distribution, age and collagen density all contribute to the adherence required to move blood back and forth. The individual heart valve leaflets are folded into shape by special collagen under variable pressure. Gradual calcium deposition in collagen occurs as a natural function of aging. The calcified points in the collagen matrix show contrast in the appearance of blood and moving muscles, enabling methods of cardiac imaging technology to achieve a ratio that basically states blood in (heart input) and blood out (cardiac output). Pathology foundation of heart collagen is understood in the category of connective tissue disease.

Cosmetic Surgery

Collagen has been widely used in cosmetic surgery, as a healing aid for burn patients for bone reconstruction and a wide range of dental, orthopedic, and surgical purposes. Human and cow collagen is widely used as a dermal filler for the treatment of wrinkles and skin aging. Some points of interest are:

1. When used cosmetically, there is the possibility of an allergic reaction causing prolonged redness; however, this can be removed by simple and inconspicuous patch testing prior to cosmetic use.
2. Most of the medical collagen is derived from a young cow (cow) from a BSE-certified animal. Most producers use donor animals from "closed flocks", or from countries that have never had reported BSE cases such as Australia, Brazil, and New Zealand.

Bone graft

When the skeleton forms the body structure, it is important to maintain its strength, even after rest and injury. Collagen is used in bone grafting because it has a structure of three helices, making it a very powerful molecule. It is ideal for use in bone, as it does not compromise the structural integrity of the skeleton. The triple helical collagen structure prevents it from being broken down by enzymes, it allows cell stickiness and is essential for proper assembly of the extracellular matrix.

Network regeneration

Collagen scaffolds are used in tissue regeneration, either in sponges, thin sheets, or gels. Collagen has the right properties for tissue regeneration such as pore structure, permeability, hydrophilicity and stable in vivo. Collagen scaffolds are also ideal for cell precipitation, such as osteoblasts and fibroblasts and once incorporated, growth may continue as normal in tissues.

Use of reconstructive surgery

Collagen is widely used in the construction of artificial skin substitutes used in the management of burns and severe injuries. These collagen can come from sources of cattle, horses, pigs, or even humans; and sometimes used in combination with silicon, glycosaminoglycans, fibroblasts, growth factors and other substances.

Wound care

Collagen is one of the key natural resources of the body and the components of skin tissue that can benefit all stages of the wound healing process. When collagen is made available to the wound bed, closure may occur. Wound damage, followed sometimes with procedures such as amputation, can be avoided.

Collagen is a natural product, therefore used as a natural wound dressing and has properties not possessed by artificial wound dressings. It is resistant to bacteria, which is very important in wound dressing. This helps to keep the wound sterile, because of its natural ability to fight off infections. When collagen is used as a burning bandage, healthy granulation tissue can form very quickly over the burn, helping to heal it quickly.

During the 4 phases of wound healing, collagen performs the following functions in wound healing:

• Guiding function: Collagen fibers serve to guide fibroblasts. Fibroblasts migrate along the connective tissue matrix.
• Chemotactic properties: Large surface areas available on collagen fibers can attract fibrogenic cells that aid healing.
• Nucleation: Collagen, in the presence of certain neutral salt molecules can act as nucleation agents that lead to the formation of fibrillar structures. Collagen dressing can serve as a guide to direct new collagen deposition and capillary growth.
• Hemostatic properties: Blood thrombocytes interact with collagen to make the hemostatic plug.

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As a supplement

When hydrolyzed, collagen is reduced to a small, digestible peptide in the form of dietary supplements or functional foods and beverages in order to aid joint and bone health and improve skin health. Hydrolyzed collagen has a much smaller molecular weight than the original collagen or gelatin, studies show that more than 90% of hydrolysed collagen is digested and available as a small peptide in the bloodstream within an hour. From peptide blood (containing hydroxyproline) is transported to target tissues, eg skin, bone and cartilage, where peptides act as building blocks for local cells and help increase the production of new collagen fibers.

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Basic research

Collagen is used in laboratory studies for cell culture, studying cell behavior and cellular interactions with extracellular environments.

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Veterinary use

Several studies have demonstrated the efficacy of collagen supplementation for dogs with osteoarthritis pain, alone or in combination with other nutraceuticals such as glucosamine and chondroitin.

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Chemistry

The collagen protein consists of a triple helix, which generally consists of two identical chains (? 1) and a slightly different additive chain in its chemical composition (? 2). The amino acid composition of atypical collagen for protein, especially with regard to its high hydroxyproline content. The most common motives in the sequence of collagen amino acids are glycine-X-proline and glycine-X-hydroxyproline, where X is an amino acid other than glycine, proline or hydroxyproline. The average amino acid composition for fish and mammalian skin is given.

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Synthesis

First, a three-dimensional stranded structure is assembled, with amino acids glycine and proline as its main component. It has not collagen but its predecessor, procollagen. Procollagen is then modified by the addition of hydroxyl groups to the proline of amino acids and lysine. This step is important for later glycosylation and the formation of a triple helix collagen structure. Because the hydroxylase enzyme that performs this reaction requires vitamin C as a cofactor, long-term deficiency in this vitamin results in impaired collagen synthesis and scurvy. This hydroxylation reaction is catalyzed by two different enzymes: prolyl-4-hydroxylase and lysyl-hydroxylase. Vitamin C also works with them in encouraging these reactions. In this service, one vitamin C molecule is destroyed for every H that is replaced by OH. Collagen synthesis occurs inside and outside the cell. The formation of collagen that produces fibrillary collagen (the most common form) is discussed here. Meshwork collagen, which is often involved in the formation of filtration systems, is another form of collagen. All types of collagen are triple helices, and the difference lies in the alpha peptide arrangement made in step 2.

1. MRNA transcription : Approximately 34 genes are associated with collagen formation, each encoding for a particular mRNA sequence, and usually having the prefix " COL ". Early collagen synthesis begins with the activation of genes associated with the formation of certain alpha peptides (usually alpha 1, 2, or 3).
2. Pre-peptide formation : After the final mRNA exits the cell nucleus and enters the cytoplasm, it is connected to the ribosomal subunit and the translation process occurs. The first/first part of the new peptide is known as the signal sequence. The signal sequence on the N-terminal peptide is recognized by the signal recognition particle in the endoplasmic reticulum, which will be responsible for directing the pre-pro-peptides into the endoplasmic reticulum. Therefore, after the synthesis of the new peptide is complete, it directly enters the endoplasmic reticulum for post-translational processing. Now known as pre-pro-collagen.
3. Pro-collagen peptides : Three pre-pro-peptide modifications occur leading to alpha peptide formation:
   1. The signal peptide on the N-terminal is dissolved, and the molecule is now known as propeptide (not procollagen).
   2. Lysine hydroxylation and prolines in propeptide by 'prolyl hydroxylase' and 'lysyl hydroxylase' enzymes (to produce hydroxyproline and hydroxylysine) occur to help cross-linking of alpha peptides. This enzymatic step requires vitamin C as a cofactor. In scurvy, lack of hydroxylation of prolines and lysines causes a loose triple helix (formed by three alpha peptides).
   3. Glycosylation occurs by adding a glucose or galactose monomer into a hydroxyl group placed into lysine, but not in the prolines.
   4. After this modification occurs, three of the hydroxylated propeptides and the winding glycosylation become triple helices form a procollagen. Procollagen still has a broken end, which will be trimmed. At this point, procollagen is bundled into a transfer vesicle intended for the Golgi apparatus.
4. modification of Golgi equipment : In the Golgi apparatus, procollagen through one final post-translational modification before removal from the cell. In this step, the oligosaccharides (not monosaccharides as in step 3) are added, and then the procollagen is packed into secretory vesicles devoted to the extracellular space.
5. Tropocollagen Formation : Once outside the cell, the membrane-bound enzyme is known as the 'collagen peptidase', releasing the "loose end" of the procollagen molecule. What remains is known as tropocollagen. Defects in this step result in one of the many collagenopathies known as Ehlers-Danlos syndrome. This step does not exist when synthesizing type III, a type of collagen fibrillar.
6. Formation of collagen fibrils : lysyl oxidase, a copper-dependent extracellular enzyme, yields the final step in the collagen synthesis pathway. This enzyme works on lysine and hydroxysin which produce aldehyde groups, which will eventually covalent bonds between the tropocollagen molecules. Polymers of this tropocollogen are known as collagen fibrils.

Amino acids

Collagen has an unusual composition and sequence of amino acids:

• Glycine is found in almost every third residue.
• Proline forms about 17% of collagen.
• Collagen contains two derived amino acids that are not directly inserted during translation. These amino acids are found in certain locations relative to glycine and are modified post-translated by different enzymes, both of which require vitamin C as a cofactor.
  • Hydroxyproline comes from the proline
  • Hydroxisin is derived from lysine - depending on the type of collagen, the amount of hydroxycin that varies is glycosylated (most have an installed disaccharide).

Cortisol stimulates the degradation of collagen (skin) into amino acids.

Collagen I formation

Most forms of collagen are the same way, but the following process is typical for type I:

1. Inside the cell
   1. Two types of alpha chains are formed during translation of the ribosome along the rough endoplasmic reticulum (RER): alpha-1 and alpha-2 chains. This peptide chain (known as preprocollagen) has a registration peptide at each end and a signal peptide.
   2. The polypeptide chain is released into the RER lumen.
   3. The signal peptide is split inside the RER and the chain is now known as a pro-alpha chain.
   4. Lysine and proline amino acid hydroxylation occurs within the lumen. This process depends on ascorbic acid (vitamin C) as a cofactor.
   5. Glycosylated specific hydroxysine residues occur.
   6. The structure of the three-alpha helix is ​​formed in the endoplasmic reticulum of two alpha-1 chains and one alpha-2 chain.
   7. Procollagen is sent to the Golgi apparatus, where it is packed and secreted by exocytosis.
2. Outside the cell
   1. The registration peptide is cleaved and the tropocollagen is formed by procollagen peptidase.
   2. Some tropocollagen molecules form collagen fibrils, via covalent crosslinking (aldolic reactions) by lysyl oxidase linking hydroxysine and lysine residues. Some collagen fibrils form into collagen fibers.
   3. Collagen can attach to the cell membrane through several types of proteins, including fibronectin, laminin, fibulin and integrin.
Synthetic pathogenesis

Vitamin C deficiency causes scurvy, a serious and painful disease in which the damaged collagen prevents the formation of a strong connective tissue. Gums worsen and bleed, with tooth loss; skin color, and wounds do not heal. Prior to the 18th century, this condition was well known among the long-term military, especially the navy, the expedition in which participants lost food containing vitamin C.

Autoimmune diseases such as lupus erythematosus or rheumatoid arthritis can attack healthy collagen fibers.

Many bacteria and viruses secrete virulence factors, such as collagenase enzymes, which destroy collagen or interfere with production.



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Molecular Structure

A single collagen molecule, tropocollagen, is used to form larger collagen aggregates, such as fibrils. It is about 300 m long and 1.5 nm in diameter, and consists of three polypeptide strands (called alpha peptides, see step 2), each has a left-handed helical conformation - this should not be confused with the right-handed alpha helix. These three left-handed helices are assembled into a right-helix or "super helix" helix, a cooperative cooperative structure stabilized by many hydrogen bonds. With type I collagen and possibly all fibrillar collagen, if not all collagen, any triple-helix association into a super-super-coil right-handed is called a collagen microfibril. Each microfibril is interdigitated with its neighboring microfibrils to a degree that may indicate they are individually unstable, although in collagen fibrils, they are very well ordered to become crystals.

Characteristic of collagen is the regular arrangement of amino acids in each of the three chains of this collagen subunit. The sequence often follows the Gly-Pro-X or Gly-X-Hyp pattern, where X may be one of many other amino acid residues. Proline or hydroxyproline is about 1/6 of the total order. By accounting for glycine to 1/3 of a sequence, this means roughly half of the collagen sequence rather than glycine, proline or hydroxyproline, a fact often overlooked by disorders of an unusual GX ₁ X ₂ collagen alpha-peptide character. The high glycine content of collagen is important with respect to the stabilization of collagen helices as this allows the association of collagen fibers closely related in the molecule, facilitating hydrogen bonding and cross-linking intermolecular formation. Regular repetitions of this kind and high glycine content are found only in some other fibrous proteins, such as fibroin silk.

Collagen is not just a structural protein. Due to the key role in the determination of cell phenotype, cell adhesion, regulation of tissues and infrastructure, many parts of the non-proline-rich region have the role of cell/matrix association/regulation. The relatively high content of the proline and hydroxyproline rings, with its geometrically limited carboxyl and the amino (secondary) group, together with abundant abundance of glycine, contribute to trends of individual polypeptide strands to form spontaneously left-handed helices, in the absence of intrachain. hydrogen bond.

Since glycine is the smallest amino acid without side chain, it plays a unique role in fibrous structural protein. In collagen, Gly is required in every third position because the triple helix assembly places this residue on the inside (axis) of the helix, where there is no room for a larger side group than a single glycine hydrogen atom. For the same reason, the Pro and Hip rings must point outwards. These two amino acids help stabilize the triple helix - even more Hyp than Pro; lower concentrations of them are required in animals such as fish, whose body temperature is lower than most warm-blooded animals. The lower proline and hydroxyproline content is characteristic of cold water, but not warm water fish; the latter tend to have proline and hydroxyproline content similar to mammals. The lower proline and hydroplotroline content of cold water fish and other poikilotherm animals cause their collagen to have lower thermal stability than mammalian collagen. Lower thermal stability means gelatin derived from collagen fish is unsuitable for many food and industrial applications.

The tropocollagen subunit spontaneously assembles itself, with its regularly staggered ends, into a larger arrangement in the extracellular space of the tissue. An additional fibril assembly is guided by fibroblasts, which store the fully formed fibrils of fibripositors. In fibrillar collagen, the molecule stumbles into adjacent molecules about 67? Nm (units referred to as 'D' and changes depending on the hydration state of aggregate). In each D-period microfibril replication, there is a section containing five molecules in a cross section, called "overlap", and a section containing only four molecules, called "gaps". These overlapping areas and gaps are retained as microfibrils converge into fibrils, and thus can be seen using an electron microscope. Tropocollagens triple helices in microfibrils are arranged in quasihexagonal packaging patterns.

There are several covalent crosslinks in the triple helix, and a number of covalent crosslinks between the tropocollagen helices form well-organized aggregates (such as fibrils). Larger fibrillar bundles are formed with the help of several different protein classes (including different types of collagen), glycoproteins and proteoglycans to form different types of adult tissues from alternative combinations of the same key players. Insoluble collagen is a barrier to monomeric collagen studies until it is found that tropocollagens from young animals can be extracted because they are not fully cross-linked. However, advances in microscopy techniques (ie electron microscopy (EM) and atomic force microscopy (AFM)) and X-ray diffraction have allowed researchers to obtain a detailed image of the collagen structure in situ . This progress is then very important to better understand the way in which collagen structures affect cells and cellular matrix communications, and how tissues are built in growth and repair, and change in development and disease. For example, using AFM-based nanoindentation has been shown that single collagen fibrils are heterogeneous materials along axial directions with significantly different mechanical properties in the gap and overlap areas, which are associated with different molecular organizations in these two regions.

Fibrils/collagen aggregates are arranged in various combinations and concentrations across various tissues to provide various properties of tissue. In bone, the entire triple helical collagen lies in a parallel arrangement and staggered. 40 nm gap between the tip of the tropocollagen subunit (approximately the same as the gap area) may serve as the nucleation site for the long, hard crystal deposition, fine crystals of the mineral component, which is a hydroxylapatite (approximately) Ca ₁₀ (OH) ₂ (PO ₄ ) ₆ . Collagen type I gives tensile strength to bone.



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Related interruptions

Collagen-related illnesses most often arise from genetic defects or nutritional deficiencies that affect biosynthesis, assembly, postranslational modification, secretion, or other processes involved in the production of normal collagen.

In addition to the above mentioned disorders, excessive collagen deposition occurs in scleroderma.



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Disease

A thousand mutations have been identified in 12 of more than 20 types of collagen. These mutations can cause various diseases at the tissue level.

Osteogenesis imperfecta - Caused by mutations in type 1 collagen , dominant autosomal disorder, resulting in weak bones and irregular connective tissue, some cases can be mild while others can be lethal. Mild cases have lower levels of collagen type 1 while severe cases have structural defects in collagen.

Chondrodysplasias - Skeletal disorders are believed to be caused by mutations in type 2 collagen , more research is underway to confirm this.

Ehlers-Danlos Syndrome - Six types of this disorder, which cause deformities in connective tissue, are known. Some species can be deadly, which causes the rupture of the arteries. Each syndrome is caused by a different mutation, for example the type of four disorders is caused by a mutation in collagen type 3 .

Alport Syndrome - Can be transmitted genetically, usually as X-linked dominant, but also as a dominant autosomal and autosomal recessive disorder, sufferers have problems with their kidneys and eyes, hearing loss can also develop during childhood or adolescence.

Osteoporosis - Not genetically inherited, due to age, associated with reduced levels of collagen in the skin and bone, growth hormone injections are being investigated as a possible treatment to combat the loss of collagen.

Knobloch syndrome - Caused by mutations in the COL18A1 gene encoding the production of collagen XVIII. Patients present with a protrusion of brain tissue and retinal degeneration, an individual who has a family member suffering from this disorder has a greater risk of developing it by itself because of a hereditary relationship.




Characteristics

Collagen is one of the long fibrous structural proteins whose functions are very different from globular proteins, such as enzymes. A difficult collection of collagen called collagen fibers is a major component of the extracellular matrix that supports most of the tissues and gives the cell structure from the outside, but collagen is also found in certain cells. Collagen has a large tensile strength, and is a major component of fascia, cartilage, ligaments, tendons, bones and skin. Along with elastin and soft keratin, it is responsible for the strength and elasticity of the skin, and its degradation causes wrinkles that accompany aging. It strengthens blood vessels and plays a role in tissue development. It is present in the cornea and eyepiece in the form of crystals. This may be one of the most abundant proteins in the fossil record, since the fossils often appear, even in the bones of the Mesozoic and Paleozoic.

Usage

Collagen has a wide range of applications, from food to medical. For example, used in cosmetic surgery and burn surgery. It is widely used in the form of collagen casing for sausage, which is also used in the manufacture of musical strings.

If collagen is sufficiently denatured, e.g. by heating, three tropocollagen strands partially or entirely separate into the globular domain, containing different secondary structures to normal collagen polyproline II (PPII), eg. random rolls. This process explains the formation of gelatin, which is used in many foods, including taste gelatin desserts. In addition to food, gelatin has been used in the pharmaceutical, cosmetic, and photographic industries.

From the Greek word for glue, , the word collagen means "glue producer" and refers to the initial process of boiling the skin and the muscles of horses and other animals to gain glue. Collagen adhesives were used by Egypt about 4,000 years ago, and Native Americans used them in bows about 1,500 years ago. The world's oldest glue, which has a carbon life of more than 8,000 years, is found as collagen - used as a protective coating on rope baskets and embroidered fabrics, and for holding shared equipment; also in crossed decorations on human skulls. Collagen is usually converted into gelatin, but survives due to dry conditions. The humidity of animals is thermoplastic, softening again after heating, so it is still used to make musical instruments such as violins and fine guitars, which may have to be reopened for repairs - applications that do not fit the permanent hard, synthetic adhesive plastics. The nerves and skins of animals, including the skin, have been used to create useful articles for thousands of years.

Gelatin-resorcinol-formaldehyde glue (and with formaldehyde replaced by less toxic pentanedial and ethanial) has been used to improve experimental incisions in rabbit lung.




History

The molecular structure and packing of collagen have eluded scientists for decades of research. The first evidence that he had a regular structure on the molecular level was presented in the mid-1930s. Since then, many prominent scholars, including Nobel Prize winners Crick, Pauling, Rich and Yonath, and others, including Brodsky, Berman, and Ramachandran, have concentrated on collagen monomer conformation. Some competing models, though correctly dealing with the conformation of individual individual peptide chains, give way to the triple-helical model of "Madras" from Ramachandran, which provides a truly precise model of molecular quarternary structure although this model still needs some improvement. The collagen packing structure has not been defined at the same level outside the fibrillar collagen type, although it has long been known as hexagonal or quasi-hexagonal. Like its monomer structure, several conflicting models allege that the packing arrangement of collagen molecules is 'sheet-like' or microfibrillar. The microfibril structure of collagen fibrils in the tendon, cornea and cartilage has been directly imaged by an electron microscope. The microfibrillar structure of the tail tendon, as described by Fraser, Miller, and Wess (among others), is modeled as closest to the observed structure, although it oversimplifies the development of neighboring collagen molecular topologies, and therefore does not predict proper conformation. of the D-periodic discontinuous pentameric arrangement is called simply: the microfibril. Various crosslinking agents such as L-Dopaquinone, embline, potassium embelate, and 5-O-methyl embelin can be developed as potential binding/stabilization agents of collagen preparation and their application as a wound dressing sheet in enhanced clinical applications.

The evolution of collagens is a fundamental step in the early evolution of life, supporting the integration of multicellular life forms.




D-appeal

Collagen D-milkfish is feasible as a periodic formation of ridging in all fibrils to form collagen. D-bands were created due to the formation of semi-crystalline collagen in fibrils. The pattern shown by D-milkfish is consistently independent of the diameter of fibrils. When deformed, collagen fibrils can lose their D-bandeng, making the loss of d-band indicator of the type of damage experienced by fibril tendon.




See also

• Collagen is hydrolyzed, a common form in which collagen is sold as a supplement
• Animal glue
• Gelatin
• Fibrous protein
• Osteoid, a bone component containing collagen
• Lysyl oxidase
• Collagenase, an enzyme involved in breakdown of collagen and remodeling
• Hypobobility syndrome
• MMP Inhibitor





References

Source of the article : Wikipedia