BP Fluor 568 (Alexa Fluor 568 equivalent; AF568) dye is a bright, orange-fluorescent dye with excitation ideally suited for the 568 nm laser line on the Ar-Kr mixed-gas laser. BF Fluor 568 dye is pH-insensitive over a wide molar range for stable signal generation in imaging and flow cytometry. BF Fluor 568 dye molecules can be attached to proteins at high molar ratios without significant self-quenching, enabling brighter conjugates and more sensitive detection. The probes with high fluorescence quantum yield and high photostability allow detection of low-abundance biological structures with great sensitivity.