Background:

Methoxy-X04 is a brain-permeable fluorescent probe for amyloid-β (Aβ) to detect and quantify plaques, tangles, and cerebrovascular amyloid.1 It displays high in vitro binding affinity (Ki = 26.8 nM) for fibrillar β-sheet deposits and is used to image Aβ plaques in the brains of living APP/PS1 mice, a transgenic model of familial Alzheimer's disease.[1],[2] For in vivo imaging, APP/PS1 mice were injected with methoxy-X04 at a dose of 10 mg/kg, i.p., 24 hours prior to two-photon imaging.2 Methoxy-X04 displays an excitation peak at 750 nm with emission between 460 and 500 nm.[2]
Reference:
[1]. Klunk, W.E., Backsai, B.J., Mathis, C.A., et al. Imaging Aβ plaques in living transgenic mice with multiphoton microscopy and methoxy-X04, a systemically administered Congo red derivative. J. Neuropathol. Exp. Neurol. 61(9), 797-805 (2002).
[2]. Burgold, S., Bittner, T., Dorostkar, M.M., et al. In vivo multiphoton imaging reveals gradual growth of newborn amyloid plaques over weeks. Acta. Neuropathol. 121(3), 327-335 (2011).