In 2016 researchers introduced collections of artificial DNA sequences into Escherichia coli and tested how the transformed cells survived in a stressful environment with toxic copper levels. The genetic codes led E. coli to produce novel proteins that were designed by researchers rather than evolved naturally. (For more on designer proteins, see Physics Today, June 2020, page 17.) One such de novo protein, a bundle of four helices known as Construct K (ConK), helped the cells withstand copper levels twice those that are fatal to an unaltered cell. The reason why was unclear, but the observation suggested that the protein transforms metal ions into stable complexes.
Now Michael Hecht of Princeton University and his colleagues have shown that ConK catalyzes the growth of cadmium sulfide quantum dots (QDs). Those nanocrystals are efficient light absorbers and emitters, and they’re promising for applications such as LEDs, in addition to displaying interesting physics because of their effective zero-dimensionality.
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