4-Thiouridine, also known as 4-SU, is a photoactivatable ribonucleoside analog that is widely used for RNA analysis, including short-range RNA-RNA crosslinking and nascent RNA labeling. The crosslinking thio moiety is attached directly to the nucleotide base, thus 4-SU differs from uridine only by a single sulfur substitution. This offers the advantage of incorporating into an RNA chain with minimal structural perturbation and with similar base-pairing properties, reducing the likelihood that substitution will impair RNA interactions or activities.

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.