<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>

CC BY-SA 4.0
2020-10-06T18:03:25.407Z
Great, thanks! Exactly what I needed.
What about ionic interaction (salt bridges), do you have the numbers?
Jake B.
CC BY-SA 4.0
2020-10-06T20:29:28.457Z
No, I'm afraid I can't help with salt bridges.
marcin
CC BY-SA 4.0
2020-10-06T15:17:34.467Z
2020-10-06T15:17:34.467Z
marcin
<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>

<proteins><database><protein-structure><pdb>
How many entries in PDB have SS bonds?
# 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

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## 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, 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.  

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