6-SFX (full name: 6-(Fluorescein-6-carboxamido)hexanoic acid, succinimidyl ester, single isomer) has a 6-atom aminohexanoyl spacer group that separates the fluorescein dye and the amine-reactive group. <ul> <li>&lamba;_Ex/&lamba;_Em (pH 9) = 494/521 nm</li> <li>Yellow solid soluble in DMF, DMSO or pH&gt;6.5 buffers</li> <li>Store at -20°C and protect from light</li> <li>C₃₁H₂₆N₂O₁₀</li> <li>MW:586.55</li> </ul>