MeSH (Medical Subject Headings)
are used to classify publications indexed by the National Library of Medicine (NLM).
MeSH is a hierarchical set of keywords applied to each publication by a human annotator.
The majority of PDB structures have associated a primary citation that is listed on the Structure Summary page.
That citation includes an abstract and keywords. The keywords are in fact MeSH terms. Thus by browsing the MeSH tree you
are finding all structures at a given level of the tree that have an abstract which include the selected MeSH term as a keyword.
Here you can browse by MeSH (Medical Subject Headings).