Silk amino acid (SAAs) also known as

Sericin Sericin is a protein created by ''Bombyx mori'' (silkworms) in the production of silk. Silk is a fibre produced by the silkworm in production of its cocoon. It consists mainly of two proteins, fibroin and sericin. Silk consists of 70–80% f ...

is a natural water-soluble glycoprotein extracted from raw silk. It is used as an additive in skin and hair care products due to its high levels of serine which has excellent moisture preservation characteristics. As a water-based additive it is used to provide a protective barrier and silky feel to

lotion Lotion is a low-viscosity topical preparation intended for application to the skin. By contrast, creams and gels have higher viscosity, typically due to lower water content. Lotions are applied to external skin with bare hands, a brush, a clean ...

soap Soap is a salt of a fatty acid used in a variety of cleansing and lubricating products. In a domestic setting, soaps are surfactants usually used for washing, bathing, and other types of housekeeping. In industrial settings, soaps are use ...

personal lubricant Personal lubricants (colloquially termed lube) are specialized lubricants used during sexual acts, such as intercourse and masturbation, to reduce friction to or between the penis and vagina, anus or other body parts or applied to sex toys to red ...

s, hair and

skincare Skin care is a range of practices that support skin integrity, enhance its appearance, and relieve skin conditions. They can include nutrition, avoidance of excessive sun exposure, and appropriate use of emollients. Practices that enhance appea ...

products. Silk amino acids are produced by

hydrolyzing Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile. Biological hydrolysis ...

(or breaking apart) silk

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...

s into smaller

peptide Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides. ...

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 Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae to form cocoons. The best-known silk is obtained from the ...

is made up of two primary proteins; a fibrous protein known as

fibroin Fibroin is an insoluble protein present in silk produced by numerous insects, such as the larvae of ''Bombyx mori'', and other moth genera such as '' Antheraea'', '' Cricula'', '' Samia'' and '' Gonometa''. Silk in its raw state consists of tw ...

, 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 (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 Alanine (symbol Ala or A), or α-alanine, is an α-amino acid that is used in the biosynthesis of proteins. It contains an amine group and a carboxylic acid group, both attached to the central carbon atom which also carries a methyl group side ...

(34.36%) *

Glycine Glycine (symbol Gly or G; ) is an amino acid that has a single hydrogen atom as its side chain. It is the simplest stable amino acid ( carbamic acid is unstable), with the chemical formula NH2‐ CH2‐ COOH. Glycine is one of the proteinog ...

(27.23%) * L- Serine (9.58%) * L-

Valine Valine (symbol Val or V) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α- amino group (which is in the protonated −NH3+ form under biological conditions), an α- carboxylic acid group (which is in the deprotona ...

(3.49%) * L- Threonine (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 Proteolysis is the breakdown of proteins into smaller polypeptides or amino acids. Uncatalysed, the hydrolysis of peptide bonds is extremely slow, taking hundreds of years. Proteolysis is typically catalysed by cellular enzymes called protease ...

, 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

{{reflist, colwidth=30em Amino acid derivatives