China
Africa
Explore chapters and articles related to this topic
Immunocytochemical Detection Systems
Published in Lars-Inge Larsson, Immunocytochemistry: Theory and Practice, 2020
Another important aspect of the avidin-biotin techniques is the properties of the avidin preparation. Natural avidin has a very high isoelectric point (above 10) and will bind nonspecifically to many tissue constituents, notably nucleic acids. The isoelectric point of avidin can be reduced by derivatizing some of its primary amino groups, and several such derivatized preparations showing less unspecific background labeling are available now. In addition, Streptomyces avidinii produce a protein, referred to as streptavidin. It possesses the strong binding avidity of egg-white avidin for biotin, yet has an isoelectric point near the neutral range and is not glycosylated.36 Streptavidin does not stick unspecifically to tissues and is the reagent of choice in the author’s laboratory. It is available from several commercial sources. A good illustration of the early problems with the stickiness of egg white avidin is that antibodies were raised to biotin and used in place of avidin. Although the use of streptavidin largely circumvents these problems, such antibodies are also commercially available, as are derivatized and less sticky avidin preparations.
Clinical Application of the Avidin-Biotin System for Tumor Targeting
Published in David M. Goldenberg, Cancer Therapy with Radiolabeled Antibodies, 1995
Giovanni Paganelli, Patrizia Magnani, Antonio G. Siccardi, Ferruccio Fazio
Avidins include proteins produced by and present in the eggs of amphibians, reptiles, and avians, currently indicated as avidins,17–18 as well as a protein produced by a streptomyces, Streptomyces avidinii, known as streptavidin. They are identical in their binding properties, but show the following differences: (1) avian avidins are glycoproteins, bearing a single-branched oligosaccharide unit (made up of mannose and glucosamine) per subunit,19 while spreptavidin is not a glycoprotein; (2) avian avidins are very basic proteins with isoelectric points of approximately 10.5; being fully dissociated as cations at physiological pH, they can interact strongly with negatively charged compounds such as acidic mucopolysaccharides or nucleic acids. In contrast, streptavidin displays isoelectric points in the range five to eight. However, avian avidins can be chemically modified, without affecting their binding properties, in order to obtain derivatives with isoelectric points close to neutrality.
Endogenous anti-streptavidin antibodies causing erroneous laboratory results more common than anticipated
Published in Scandinavian Journal of Clinical and Laboratory Investigation, 2021
Louise K. Dahll, Ellen Marie Haave, Sandra R. Dahl, Finn Erik Aas, Per M. Thorsby
The protein streptavidin is extracted from the soil-bacterium Streptomyces avidinii. The circumstances that lead to immunisation against streptavidin in humans are unknown [10]. A continuum of ASA IgM reactivity is found in the general population. It is hypothesized that since many people are exposed to these soil bacteria in their outdoor activities they may develop an immunological reaction to it [11].