text: user4449: Is there a way to figure out what percentage of entries in PDB have SS bonds?
  In addition, what other types of bonds in PDB may be worth looking into (not H bonds)?
  
  user266: The easiest way is to check annotations in mmCIF or PDB files.
  Looking at my page with statistics of mmCIF tags, last updated in March:
  _struct_conn_type.id        59137×metalc 42706×covale 36195×disulf 10725×hydrog
  _struct_conn.conn_type_id   5350402×hydrog 1733277×metalc 559092×covale 226472×disulf
  
  Which means 226472 disulfide bonds in 36195 PDB entries at the time when the PDB had 161470 entries.
  
original_text: 4449: <p>Is there a way to figure out what percentage of entries in PDB have SS bonds?
  In addition, what other types of bonds in PDB may be worth looking into (not H bonds)?</p>
   266: <p>The easiest way is to check annotations in mmCIF or PDB files.</p>
  <p>Looking at my page with <a href="https://project-gemmi.github.io/pdb-stats/tags.html" rel="nofollow noreferrer">statistics of mmCIF tags</a>, last updated in March:</p>
  <pre><code>_struct_conn_type.id        59137×metalc 42706×covale 36195×disulf 10725×hydrog
  _struct_conn.conn_type_id   5350402×hydrog 1733277×metalc 559092×covale 226472×disulf
  </code></pre>
  <p>Which means 226472 disulfide bonds in 36195 PDB entries at the time when the PDB had 161470 entries.</p>
  