β-Amyloid ELISAs

Tools for Alzheimer's Disease Research

β-Amyloid peptide (Aβ), a 40 to 43 amino acid peptide cleaved from amyloid precursor protein (APP) by b-and g-secretases, is an early and critical feature of Alzheimer disease (AD). It is the major protein component of the protein deposits in neurofibrillary tangles, neuritic plaques, and neurophil threads in the cerebral cortex of AD and Down syndrome patients. The increased release of Ab42/Ab43 leads to the abnormal deposition of human Ab and the associated neurotoxicity in the brains of affected individuals.^{1, 2}

Solid phase human Ab40 (Prod. No. BE0100) and human Ab42 (Prod. No. BE0200) ELISAs are designed for in vitro quantitative detection of human Ab peptides in sera, cell culture supernatants and EDTA plasma and CSF. The assays recognize both natural and recombinant forms of human Ab. The detection antibodies used in these kits are capable of selective differentiation between human Ab40 and Ab42/Ab43. In both assays, an antibody specific for the NH2-terminus of human Ab is coated onto the wells of a multiwell plate and binds human Ab 1-40 or 1-42 present in samples or standards. A second antibody specific for the 1-40 or 1-42 sequence of human Ab binds to the immobilized protein. After substrate addition, the reaction is visualized at 450 nm in the multiwell plate reader. The intensity of the color is directly proportional to the concentration of the human Ab present in sample or standard. The assays are highly sensitive (detect human Ab below 10 pg/mL), specific, fast (6.5 hours total time) and simple (offer precoated plates, all incubations proceed at room temperature and the reagents are supplied ready to use).

Performance Characteristics

• Precision
• Very low intra-assay variability from 1.1% to 3.6%
• Very low inter-assay variability from 1.7% to 3.7%
• Linearity of dilution – correlation coefficient for various dilutions was 0.99 for both assays
• Recovery – average recovery: sera 100%, EDTA plasma 92.8%, cerebrospinal fluid (CSF) 98%, cell culture supernatants 101-109%.

Components

• Standards: Ab 1-40, human (A1478) or Ab 1-42, human (A1853), lyophilized synthetic peptides
• Standard/Sample Diluent
• Anti-Ab, human, NH₂-Terminus Specific Antibody coated on 96 multiwell plate
• Anti-Ab 1-40, human (A1228) or Anti-Ab 1-42, human (A1728)
• Anti-Rabbit IgG-HRP
• HRP Diluent
• Wash Buffer 100X Concentrate
• Stabilized TMB Chromogen
• Stop Solution
• Plate Sealers

References

1. Sambamurti, K., et al., Neuromolecular Med., 1, 1-31 (2002).
2. Lorenzo, A., et al., Nat. Neurosci., 3, 460-464 (2000).
3. Vassar, R., et al., Science, 286, 735-741 (1999).

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