Fab fragment antibodies are generated by papain digestion of whole IgG antibodies to remove the entire Fc portion, including the hinge region. These antibodies are monovalent, containing only a single antigen binding site. The molecular weight of Fab fragments is about 50 kDa.
Store freeze-dried powder at 2-8°C. When ready to use, rehydrate with indicated volume of d. water and centrifuge if not clear. Product is stable for about 6 weeks at 2-8°C as an undiluted liquid. Prepare working dilution fresh each day. For extended storage after rehydration, add an equal volume of glycerol (ACS grade or better) for a final concentration of 50%, and store at -20°C as a liquid. Note: after the addition of glycerol, the concentration of protein and buffer salts is one-half of the original. Alternatively, aliquot and freeze the product at -70°C or below in the absence of glycerol. Avoid repeated freezing and thawing.
Expiration date: one year from date of rehydration. However, the expiration date may be extended if the product is stored according to the recommendation and the test results are acceptable for its intended use.
1:200 - 1:1000 for sequential labeling applications.
To complex with primary antibody in solution, use 1:1 weight ratio of Fab:primary antibody (15:1 molar ratio). Vortex and incubate for 30 minutes at room temperature prior to use. Titrate complex to optimal dilution for assay.
Dilution factors are presented in the form of a range because the optimal dilution is a function of many factors, such as antigen density, permeability, etc. The actual dilution used must be determined empirically.
Biotin-SP is our trade name for biotin with a 6-atom spacer positioned between biotin and the protein to which it is conjugated. When Biotin-SP-conjugated antibodies are used in enzyme immunoassays, there is an increase in sensitivity compared to biotin-conjugated antibodies without the spacer. This is especially notable when Biotin-SP conjugated antibodies are used with alkaline phosphatase-conjugated streptavidin. Apparently, the long spacer extends the biotin moiety away from the antibody surface, making it more accessible to binding sites on streptavidin. Biotinylated antibodies require an additional reagent for visualization. We offer streptavidin and Mouse Anti-Biotin conjugated to fluorophores and enzymes.
This product is for IN VITRO RESEARCH USE ONLY. It is not a medical device and it is not intended for diagnostic or therapeutic purposes.