Extinction Coefficient Excitation Maximum: 82000; Fluorescence Quantum Yield: 1 ROX NHS ester, 5-isomer is a ROX dye derivative that is commonly used for oligonucleotide labeling. The NHS ester can react specifically and efficiently with primary amines such as the side chain of lysine residue or aminosilane-coated surfaces at neutral or slight basic conditions to form a covalent bond.