Novel xanthene dyes are disclosed which excite in the range of 450-650 nm and which will emit to the red of fluoroscein. These dyes may be coupled to tagging agents, such as monoclonal antibodies, and used to detect cells in a sample....http://www.google.de/patents/US5066580?utm_source=gb-gplus-sharePatent US5066580 - Xanthene dyes that emit to the red of fluorescein
