Uranium is a key element used in nuclear energy production and is crucial in many other applications. The most stable and relevant uranium ion in aerobic environments is the uranyl cation. Super Uranyl-binding Protein(SUP) has been rationally designed via structural calculations and functional modification to specifically bind uranyl cations. According to the researchers’ results, SUP is thermodynamically stable and offers very high affinity and selectivity for uranyl with a Kd of 7.4 fM and >10,000-fold selectivity over other metal ions¹. The binding features of SUP are described later in more detail (Fig.1).

It was found that UO22+ is coordinated by five carboxylate oxygen atoms from four amino acid residues in SUP. The hydrogen bonds between the amino acid residues coordinating UO22+ and residues in its second coordination sphere also affects the protein’s uranyl binding ability (Fig.2) ².

As mentioned above, we fused SUP to three SpyTags in order to construct the 3A-SUP monomer, so the function of SUP might be affected by these additional modules. To make sure that 3A-SUP could still function when bound in the hydrogel, we tested its ability to adsorb UO22+ in various environments.