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Secondary Structure Content

Search by the percentage of alpha helix and beta sheet content or by the number of alpha helices and beta sheets.

This search queries the PDB by the content of alpha helix vs. beta sheet as defined by the authors and annotated in the HELIX and SHEET records in the PDB file. Searches can be based on the percent content of helices and/or sheets, or on the number of helices are sheets.


  1. Enter 85 for "Alpha Helices", "Percent", "min" and leave all other boxes empty to search for structures that are predominantly (at least 85%) alpha helix.
  2. Enter:

    3 for "Alpha Helices", "Number", "min"

    4 for "Alpha Helices", "Number", "max"

    3 for "Beta Sheets", "Number", "min"

    4 for "Beta Sheets", "Number", "max"

    Leave the other boxes ("Percent") empty.

    This returns all structures that have 3 or 4 alpha helices and 3 or 4 beta sheets according to the secondary structure provided by the authors.