Fluorescein-PEG4-Acid is a xanthene dye with excitation/emission maximum 494/517 nm and a free terminal carboxyl acid. Terminal carboxylic acids can react with primary amine groups in the presence of of activators (e.g. EDC, or DCC) to form a stable amide bond. It can be used as a quantum yield standard. The hydrophilic PEG spacer increases solubility in aqueous media and reduces steric hindrance during binding.

Providing storage is as stated on the product vial and the vial is kept tightly sealed, the product can be stored for up to 24 months.
Wherever possible, you should prepare and use solutions on the same day. However, if you need to make up stock solutions in advance, we recommend that you store the solution as aliquots in tightly sealed vials at -20°C. Generally, these will be useable for up to one month. Before use, and prior to opening the vial we recommend that you allow your product to equilibrate to room temperature for at least 1 hour.