A literature navigation and ranking system for scientific articles from PubMed Central. BioKI:Enzymes locates low-frequency information in full texts with convenient display of the context at different levels of detail. Designed as a two-step process, BioKI allows the user a high degree of control over a keyword-based ranking of articles retrieved by the PubMed Central search engine. The IR component of BioKI was tested in TREC Genomics 2006.