Silk amino acid (SAAs) also known as
Sericin is a natural water-soluble
glycoprotein
Glycoproteins are proteins which contain oligosaccharide chains covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycos ...
extracted from raw silk. It is used as an additive in skin and hair care products due to its high levels of
serine
Serine (symbol Ser or S) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated − form under biological conditions), a carboxyl group (which is in the deprotonated − form un ...
which has excellent moisture preservation characteristics.
As a water-based additive it is used to provide a protective barrier and silky feel to
lotions,
soaps,
personal lubricants,
hair
Hair is a protein filament that grows from follicles found in the dermis. Hair is one of the defining characteristics of mammals.
The human body, apart from areas of glabrous skin, is covered in follicles which produce thick terminal and f ...
and
skincare products. Silk amino acids are produced by
hydrolyzing (or breaking apart) silk
proteins into smaller
peptide chains, typically 18 to 19 amino acids in length. Silk amino acids have a lower molecular weight than silk protein powders and are moisturizing to skin and hair.
Silk amino acids are used in formulating shampoos, conditioner, hair treatments, bodywash, body lotions, cleansers, toners and facial moisturizers, mascara, lipstick and color cosmetics.
Background
Silk is made up of two primary proteins; a fibrous protein known as
fibroin, and a sticky protein known as sericin, with the two comprising 70–80% and 20–30% of silk, respectively. Both of these proteins provide the unique functionality of silk that makes silk clothes so unique and so popular, with the production of silk material dating back to as early as 3500 BC. What is not so well known though is that silk has been used in traditional medicine in both China and Korea for centuries. The source of these silk amino acids is typically the domesticated moth,
silkworm
The domestic silk moth (''Bombyx mori''), is an insect from the moth family Bombycidae. It is the closest relative of ''Bombyx mandarina'', the wild silk moth. The silkworm is the larva or caterpillar of a silk moth. It is an economically imp ...
(Latin name: ''Bombyx mori'').
Sericin has a high hydroxy amino acid content which is important for the water-binding capacity which regulates the
skin's moisture content. It also has a unique carbohydrate moiety and a unique repetitive amino acid sequence which give it a high affinity for bonding to adhering proteins resulting in a tightening, anti-wrinkle effect. In addition, because of its high molecular weight, it leaves a substantive semi-occlusive film that persists even after washing, and can increase the skins permeability.
Composition
Predominant composition of silk amino acids (by weight*):
* L-
Alanine (34.36%)
*
Glycine (27.23%)
* L-
Serine
Serine (symbol Ser or S) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated − form under biological conditions), a carboxyl group (which is in the deprotonated − form un ...
(9.58%)
* L-
Valine (3.49%)
* L-
Threonine
Threonine (symbol Thr or T) is an amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated −NH form under biological conditions), a carboxyl group (which is in the deprotonated −COO� ...
(2.00%)
*
SAAs contains other amino acids but only those representing >2.00% are listed due to their greater relevance
Applications
Due to its proteinous nature, sericin is susceptible to the action of
proteolytic enzymes, making it digestible; and because of properties like its gelling ability, moisture retention capacity and skin adhesion, it has numerous medical, pharmaceutical and cosmetic applications.
References
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Amino acid derivatives