From the NCBI home page, click on the Domains & Structures category on the left side of the page.
Click on 3D Domains under Databases.
Click on Preview/Index to view the list of available fields.
Find all structures of mammalian proteins containing only 2 helices and 2 strands. Use the fields [organism],[helixcount] and [strandcount], and add 'AND 0[domainno]' to limit to full protein chains (rather than internal 3D domains).
Find all polypeptide chains containing between 10 and 20 3D domains. First use the [domainno]
field and the range operator ":". Example: 5:8[domainno] gives 5-8 3D domains. Find
the polypeptide with the largest number of 3D domains. How many does it have?