Howie Alexander J, Brewer Douglas B
Department of Pathology, University College London, London, UK.
Micron. 2009 Apr;40(3):285-301. doi: 10.1016/j.micron.2008.10.002. Epub 2008 Oct 15.
Amyloid stained by Congo red has striking optical properties that generally have been poorly described and inadequately explained, although they can be understood from principles of physical optics. Molecules of Congo red are orientated on amyloid fibrils, and so the dye becomes dichroic and birefringent. The birefringence varies with wavelength in accordance with a fundamental property of all light-transmitting materials called anomalous dispersion of the refractive index around an absorption peak. The combination of this and absorption of light, with modification by any additional birefringence in the optical system, explains the various colours that can be seen in Congo red-stained amyloid between crossed polariser and analyser, and also when the polariser and analyser are progressively uncrossed. These are called anomalous colours.
经刚果红染色的淀粉样蛋白具有显著的光学特性，尽管从物理光学原理可以理解这些特性，但总体上对其描述甚少且解释不足。刚果红分子在淀粉样纤维上定向排列，因此该染料具有二向色性和双折射性。双折射随波长变化，这符合所有透光材料的一个基本特性，即在吸收峰附近折射率的反常色散。这种特性与光的吸收相结合，并受到光学系统中任何额外双折射的影响，解释了在正交偏振器和检偏器之间观察刚果红染色淀粉样蛋白时，以及当偏振器和检偏器逐渐解正交时可以看到的各种颜色。这些颜色被称为异常颜色。
