In biochemistry, avidity refers to the accumulated strength of multiple affinities of individual non-covalent binding interactions, such as between a protein receptor and its ligand, and is commonly referred to as functional affinity. Avidity differs from affinity, which describes the strength of a single interaction. However, because individual binding events increase the likelihood of occurrence of other interactions (i.e., increase the local concentration of each binding partner in proximity to the binding site), avidity should not be thought of as the mere sum of its constituent affinities but as the combined effect of all affinities participating in the biomolecular interaction. A particular important aspect relates to the phenomenon of 'avidity entropy'.[1] Biomolecules often form heterogenous complexes or homogeneous oligomers and multimers or polymers. If clustered proteins form an organized matrix, such as the clathrin-coat, the interaction is described as a matricity.[citation needed]
Avidity is commonly applied to antibody interactions in which multiple antigen-binding sites simultaneously interact with the target antigenicepitopes, often in multimerized structures. 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 weak interaction is likely to be restored.[citation needed]
Each antibody has at least two antigen-binding sites, therefore antibodies are bivalent to multivalent. Avidity (functional affinity) is the accumulated strength of multiple affinities.[2] For example, IgM is said to have low affinity but high avidity because it has 10 weak binding sites for antigen as opposed to the 2 stronger binding sites of IgG, IgE and IgD with higher single binding affinities.[citation needed]
Affinity
Binding affinity is a measure of dynamic equilibrium of the ratio of on-rate (kon) and off-rate (koff) under specific concentrations of reactants. The affinity constant, Ka, is the inverse of the dissociation constant, Kd. The strength of complex formation in solution is related to the stability constants of complexes, however in case of large biomolecules, such as receptor-ligand pairs, their interaction is also dependent on other structural and thermodynamic properties of reactants plus their orientation and immobilization.[citation needed]
Avidity tests for rubella virus, Toxoplasma gondii, cytomegalovirus (CMV), varicella zoster virus, human immunodeficiency virus (HIV), hepatitis viruses, Epstein–Barr virus, and others were developed a few years ago. These tests help to distinguish acute, recurrent or past infection by avidity of marker-specific IgG. Currently there are two avidity assays in use. These are the well known chaotropic (conventional) assay and the recently developed AVIcomp (avidity competition) assay.[4]
A number of technologies exist to characterise the avidity of molecular interactions including switchSENSE and surface plasmon resonance.[5][6]
References
^Kitov PI, Bundle DR (December 2003). "On the nature of the multivalency effect: a thermodynamic model". Journal of the American Chemical Society. 125 (52): 16271–84. doi:10.1021/ja038223n. PMID 14692768.
^Rudnick SI, Adams GP (April 2009). "Affinity and avidity in antibody-based tumor targeting". Cancer Biotherapy & Radiopharmaceuticals. 24 (2): 155–61. doi:10.1089/cbr.2009.0627. PMC2902227. PMID 19409036.
^Janeway CA, Travers P, Walport M, Shlomchik MJ (2001). Immunobiology (5th ed.). New York: Garland Science. p. 104. ISBN0-8153-3642-X.[page needed]
^Curdt I, Praast G, Sickinger E, Schultess J, Herold I, Braun HB, et al. (March 2009). "Development of fully automated determination of marker-specific immunoglobulin G (IgG) avidity based on the avidity competition assay format: application for Abbott Architect cytomegalovirus and Toxo IgG Avidity assays". Journal of Clinical Microbiology. 47 (3): 603–13. doi:10.1128/JCM.01076-08. PMC2650902. PMID 19129411.
^Gjelstrup LC, Kaspersen JD, Behrens MA, Pedersen JS, Thiel S, Kingshott P, et al. (February 2012). "The role of nanometer-scaled ligand patterns in polyvalent binding by large mannan-binding lectin oligomers". Journal of Immunology. 188 (3): 1292–306. doi:10.4049/jimmunol.1103012. PMID 22219330.
^Vorup-Jensen T (December 2012). "On the roles of polyvalent binding in immune recognition: perspectives in the nanoscience of immunology and the immune response to nanomedicines". Advanced Drug Delivery Reviews. 64 (15): 1759–81. doi:10.1016/j.addr.2012.06.003. PMID 22705545.
Further reading
Roitt IM, Brostoff J, Male DK (2001). Immunology (6th ed.). Mosby Publishers. p. 72. ISBN978-0-7234-3189-3.
avidity, biochemistry, avidity, refers, accumulated, strength, multiple, affinities, individual, covalent, binding, interactions, such, between, protein, receptor, ligand, commonly, referred, functional, affinity, differs, from, affinity, which, describes, str. In biochemistry avidity refers to the accumulated strength of multiple affinities of individual non covalent binding interactions such as between a protein receptor and its ligand and is commonly referred to as functional affinity Avidity differs from affinity which describes the strength of a single interaction However because individual binding events increase the likelihood of occurrence of other interactions i e increase the local concentration of each binding partner in proximity to the binding site avidity should not be thought of as the mere sum of its constituent affinities but as the combined effect of all affinities participating in the biomolecular interaction A particular important aspect relates to the phenomenon of avidity entropy 1 Biomolecules often form heterogenous complexes or homogeneous oligomers and multimers or polymers If clustered proteins form an organized matrix such as the clathrin coat the interaction is described as a matricity citation needed Contents 1 Antibody antigen interaction 1 1 Affinity 2 Application 3 See also 4 References 5 Further reading 6 External linksAntibody antigen interaction EditAvidity is commonly applied to antibody interactions in which multiple antigen binding sites simultaneously interact with the target antigenic epitopes often in multimerized structures 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 weak interaction is likely to be restored citation needed Each antibody has at least two antigen binding sites therefore antibodies are bivalent to multivalent Avidity functional affinity is the accumulated strength of multiple affinities 2 For example IgM is said to have low affinity but high avidity because it has 10 weak binding sites for antigen as opposed to the 2 stronger binding sites of IgG IgE and IgD with higher single binding affinities citation needed Affinity Edit Binding affinity is a measure of dynamic equilibrium of the ratio of on rate kon and off rate koff under specific concentrations of reactants The affinity constant Ka is the inverse of the dissociation constant Kd The strength of complex formation in solution is related to the stability constants of complexes however in case of large biomolecules such as receptor ligand pairs their interaction is also dependent on other structural and thermodynamic properties of reactants plus their orientation and immobilization citation needed There are several methods to investigate protein protein interactions existing with differences in immobilization of each reactant in 2D or 3D orientation The measured affinities are stored in public databases such as the Ki Database and BindingDB citation needed As an example affinity is the binding strength between the complex structures of the epitope of antigenic determinant and paratope of antigen binding site of an antibody Participating non covalent interactions may include hydrogen bonds electrostatic bonds van der Waals forces and hydrophobic forces 3 Calculation of binding affinity for bimolecular reaction 1 antibody binding site per 1 antigen Ab Ag AbAg displaystyle ce Ab Ag lt gt AbAg where Ab is the antibody concentration and Ag is the antigen concentration either in free Ab Ag or bound AbAg state calculation of association constant or equilibrium constant K a k on k off AbAg Ab Ag displaystyle K a frac k ce on k ce off frac ce AbAg ce Ab Ag calculation of dissociation constant K d k off k on Ab Ag AbAg displaystyle K d frac k ce off k ce on frac ce Ab Ag ce AbAg Application EditAvidity tests for rubella virus Toxoplasma gondii cytomegalovirus CMV varicella zoster virus human immunodeficiency virus HIV hepatitis viruses Epstein Barr virus and others were developed a few years ago These tests help to distinguish acute recurrent or past infection by avidity of marker specific IgG Currently there are two avidity assays in use These are the well known chaotropic conventional assay and the recently developed AVIcomp avidity competition assay 4 See also EditAmino acid residue Epitope Fab region HaptenA number of technologies exist to characterise the avidity of molecular interactions including switchSENSE and surface plasmon resonance 5 6 References Edit Kitov PI Bundle DR December 2003 On the nature of the multivalency effect a thermodynamic model Journal of the American Chemical Society 125 52 16271 84 doi 10 1021 ja038223n PMID 14692768 Rudnick SI Adams GP April 2009 Affinity and avidity in antibody based tumor targeting Cancer Biotherapy amp Radiopharmaceuticals 24 2 155 61 doi 10 1089 cbr 2009 0627 PMC 2902227 PMID 19409036 Janeway CA Travers P Walport M Shlomchik MJ 2001 Immunobiology 5th ed New York Garland Science p 104 ISBN 0 8153 3642 X page needed Curdt I Praast G Sickinger E Schultess J Herold I Braun HB et al March 2009 Development of fully automated determination of marker specific immunoglobulin G IgG avidity based on the avidity competition assay format application for Abbott Architect cytomegalovirus and Toxo IgG Avidity assays Journal of Clinical Microbiology 47 3 603 13 doi 10 1128 JCM 01076 08 PMC 2650902 PMID 19129411 Gjelstrup LC Kaspersen JD Behrens MA Pedersen JS Thiel S Kingshott P et al February 2012 The role of nanometer scaled ligand patterns in polyvalent binding by large mannan binding lectin oligomers Journal of Immunology 188 3 1292 306 doi 10 4049 jimmunol 1103012 PMID 22219330 Vorup Jensen T December 2012 On the roles of polyvalent binding in immune recognition perspectives in the nanoscience of immunology and the immune response to nanomedicines Advanced Drug Delivery Reviews 64 15 1759 81 doi 10 1016 j addr 2012 06 003 PMID 22705545 Further reading EditRoitt IM Brostoff J Male DK 2001 Immunology 6th ed Mosby Publishers p 72 ISBN 978 0 7234 3189 3 External links EditAntibody Avidity at the US National Library of Medicine Medical Subject Headings MeSH Retrieved from https en wikipedia org w index php title Avidity amp oldid 1113459280, wikipedia, wiki, book, books, library,
