BP Fluor 405 NHS Ester is a water-soluble blue fluorescent dye commonly utilized in multicolor applications, such as flow cytometry and super-resolution microscopy using STORM. It is optimally excited by the 407 nm spectral line of krypton lasers or 408 nm violet laser diodes. The binding compounds of BP Fluor 405 are pH insensitive from pH 4 to pH 10. NHS esters (or succinimidyl esters) are highly preferred amine-reactive groups for labeling primary amines in proteins (Lys), amine-modified oligonucleotides, and other amine-containing molecules. Proteins can be labeled with BP Fluor 405 NHS Ester at high molar ratios without significant self-quenching, resulting in brighter conjugates and more sensitive detection. Additionally, BP Fluor 405 conjugates can be employed for detecting abundant targets.