Filamentous fusion phage: Novel expression vectors that display cloned antigens on the virion surface.

In this paper Smith invented "phage display technology," a technique where a specific protein sequence is artifically inserted into the coat protein gene of a bacteriophage, causing the protein to be expressed on the outside of the bacteriophage.  In 2018 Smith shared half of the Nobel Prize in Chemistry with Sir Gregory Winter  "for the phage display of peptides and antibodies."

(Thanks to Juan Weiss for this reference and its interpretation.)