Answers.Body: <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>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-10-06T18:03:25.407Z
Answers.Text: Great, thanks! Exactly what I needed.
  What about ionic interaction (salt bridges), do you have the numbers?
Answers.UserDisplayName: Jake B.
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-10-06T20:29:28.457Z
Answers.Text: No, I'm afraid I can't help with salt bridges.
Answers.UserDisplayName: marcin
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-10-06T15:17:34.467Z
Answers.LastActivityDate: 2020-10-06T15:17:34.467Z
Answers.UserDisplayName: marcin
Body: <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>
  
Tags: <proteins><database><protein-structure><pdb>
Title: How many entries in PDB have SS bonds?
ThreadText: # How many entries in PDB have SS bonds?
  
  (Asked by: username_0 on 2020-10-06)
  
  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)?
  
  **Tags:** proteins, database, protein-structure, pdb
  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_1 on 2020-10-06. Score: 3
  
  The easiest way is to check annotations in mmCIF or PDB files.
  
  Looking at my page with [statistics of mmCIF tags](https://project-gemmi.github.io/pdb-stats/tags.html), 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.
  
  > **Comments:**
  > **username_0**: Great, thanks! Exactly what I needed. What about ionic interaction (salt bridges), do you have the numbers?  
  > **username_1**: No, I'm afraid I can't help with salt bridges.  
  
  ---
  
  