Tunable biopolymers were synthesized for the removal of heavy metals from d
ilute waste streams. Protein-protein interaction was tailored specifically
into tunable, metal-binding biopolymers using elastin-like polypeptides com
posed of either one or two hexahistidine clusters. These tunable biopolymer
s retained the functionality of the elastin domain, undergoing a reversible
phase transition above the transition temperature. Aggregation could be tu
ned within a wide range of temperatures by controlling the chain length of
the biopolymers. The presence of the histidine clusters enabled Cd2+ to bin
d strongly to the biopolymers. Recovery of biopolymer-Cd2+ complexes was ea
sily achieved by triggering aggregation either by raising temperature or by
salt addition. Regenerated biopolymers could be reloaded with Cd2+ and reu
sed for repeated cycles with similar efficiency. This system is very flexib
le as both domains can be engineered to respond to various phase transition
conditions and to provide various levels of metal-binding selectivity. The
ability to modulate the properties of the biopolymers simply by tuning pro
cess conditions should open up new opportunities for the separation and rec
overy of other environmental contaminants.