Chrysamine G (CG) is a carboxylic acid analogue of Congo red, a histologic dye which stains amyloid. CG binds to the b-amyloid protein of Alzheimer''s disease (AD) in vitro and partitions into the brain of normal mice. The binding of CG is correlated with numbers of senile plaques and neurofibrillary tangles. CG displays both high (Kd = 200 nM; Bmax = 1.13 moles per mole of Ab40) and low (Kd = 38.77 mM; Bmax = 23.10 moles per mole of Ab40) affinity binding sites for b-amyloid (Ab) fibrils. It can cross the blood-brain barrier and serve as an useful probe for detecting senile plaques (Ab aggregate). In addition, CG can be used to stain cerebrovascular amyloid in tissue sections.
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