BP Fluor 555 (Alexa Fluor 555 equivalent; AF555) is a water-soluble, bright orange-fluorescent dye with excitation ideally suited for the 532 nm or 555 nm laser lines and visualized with TRITC (tetramethylrhodamine) filter sets. BP Fluor 555 conjugates of antibodies, peptides, and proteins are pH insensitive from pH 4 to pH 10. Proteins can be labeled with BP Fluor 555 NHS Ester at high molar ratios without significant self-quenching, leading to brighter conjugates and more sensitive detection. BP Fluor 555 conjugates ideally suited for detection of low abundance targets.