Avidity
Encyclopedia
In protein
s, avidity is a term used to describe the combined strength of multiple bond
interactions. Avidity is distinct from affinity
, which is a term used to describe the strength of a single bond. As such, avidity is the combined synergistic
strength of bond affinities rather than the sum of bonds.
It is commonly applied to antibody
interactions in which multiple antigen binding sites simultaneously interact with a target. Individually, each binding interaction may be readily broken, however, when many binding interactions are present at the same time, transient unbinding of a single site does not allow the molecule to diffuse away, and binding of that site is likely to be reinstated. The overall effect is synergistic, strong binding of antigen to antibody (e.g. IgM
is said to have low affinity but high avidity because it has 10 weak binding sites as opposed to the 2 strong binding sites of IgG, IgE
and IgD
).
If the clustered proteins form a matrix, such as a clathrin
-coat, the interaction is described by the term matricity
.
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s, avidity is a term used to describe the combined strength of multiple bond
Covalent bond
A covalent bond is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms. The stable balance of attractive and repulsive forces between atoms when they share electrons is known as covalent bonding....
interactions. Avidity is distinct from affinity
Chemical affinity
In chemical physics and physical chemistry, chemical affinity is the electronic property by which dissimilar chemical species are capable of forming chemical compounds...
, which is a term used to describe the strength of a single bond. As such, avidity is the combined synergistic
Synergy
Synergy may be defined as two or more things functioning together to produce a result not independently obtainable.The term synergy comes from the Greek word from , , meaning "working together".-Definitions and usages:...
strength of bond affinities rather than the sum of bonds.
It is commonly applied to antibody
Antibody
An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen...
interactions in which multiple antigen binding sites simultaneously interact with a target. Individually, each binding interaction may be readily broken, however, when many binding interactions are present at the same time, transient unbinding of a single site does not allow the molecule to diffuse away, and binding of that site is likely to be reinstated. The overall effect is synergistic, strong binding of antigen to antibody (e.g. IgM
IGM
IGM as an acronym or abbreviation can refer to:* Immunoglobulin M , the primary antibody against A and B antigens on red blood cells* International Grandmaster, a chess ranking* intergalactic medium* Intragroup medium - see: Intracluster medium...
is said to have low affinity but high avidity because it has 10 weak binding sites as opposed to the 2 strong binding sites of IgG, IgE
IGE
IGE was one of the largest services company buying and selling virtual currencies and accounts for MMORPG. During its peak time, it had offices in Los Angeles, China , and headquarters & customer service centre in Hong Kong. IGE was one of the main monopoly in virtual economy services, also known...
and IgD
IGD
IGD can refer to:*Internet Gateway Device as defined in UPnP.*İGD, İlerici Gençler Derneği, Progressive Young Association of Turkey*Immunoglobulin D, an antibody protein involved in the maturation of B cells....
).
If the clustered proteins form a matrix, such as a clathrin
Clathrin
Clathrin is a protein that plays a major role in the formation of coated vesicles. Clathrin was first isolated and named by Barbara Pearse in 1975. It forms a triskelion shape composed of three clathrin heavy chains and three light chains. When the triskelia interact they form a polyhedral lattice...
-coat, the interaction is described by the term matricity
Matricity
Matricity is the interaction of a matrix with its environment. This word is used particularly of protein interactions, where a polymerised protein interacts with a membrane or another polymer....
.