<p><strong>EDIT:</strong> </p>

<p>Actually, after having a more thorough look into the documentation; <code>REMARK 3</code> might be the more relevant to what you need. Other tools are reported in that section. </p>

<blockquote>
  <p>REMARK 3 presents information on refinement program(s) used and related statistics. For non-diffraction studies, REMARK 3 is used to describe any refinement done, but its format is mostly free text.</p>
</blockquote>

<p><a href="http://www.wwpdb.org/documentation/file-format-content/format33/remark3.html" rel="nofollow noreferrer" title="More on `Remark 3`">More on <code>Remark 3</code></a></p>

<hr>

<p>From the same source as you reference yourself <a href="http://www.wwpdb.org/documentation/file-format-content/format33/remarks1.html" rel="nofollow noreferrer" title="v 3.3">v 3.3</a>, I would argue that 
<code>REMARK 0</code> would be more accurate than <code>REMARK 250</code>.</p>

<blockquote>
  <p>REMARK 0 (updated), Re-refinement notice
  REMARK 0 identifies entries in which a re-refinement has been performed using the data from an existing entry. This remark also describes the PDB code and the journal records for the original data set.</p>
</blockquote>

<p>While when you consider the definition of <code>REMARK 250</code></p>

<p>-- which follows directly:</p>

<ul>
<li><code>REMARK 205</code> (specific to Fiber diffraction experiment), </li>
<li><code>REMARK 201</code>(and <code>REMARK 215/217</code> all specific to NMR experiment),</li>
<li><code>REMARK 230</code> (neutron diffraction study), </li>
<li><code>REMARK 240</code>(electron crystallography study) and </li>
<li><code>REMARK 245</code>(and <code>REMARK 247</code>: specific to EM study)</li>
</ul>

<blockquote>
  <p>REMARK 250, Other Type of Experiment Details</p>
  
  <p>REMARKs specific to other kinds of studies, not listed above. 
  REMARK 250 is mandatory if other than X-ray, NMR, neutron, or electron study. The format of the date in this remark is DD-MMM-YY. DD is the day of the month (a number 01 through 31), MMM is the English 3-letter abbreviation for the month, and YY is the year.</p>
</blockquote>

<p>and then <code>REMARK 265</code> is also about the crystallography experiment.</p>

<p>Hence, I know that personally, I usually assume that whatever is annotated in <code>REMARK 250</code>is relevant to the first acquisition experiment to me.</p>

<p>Another reason I am more inclined to think <code>REMARK 0</code>is more accurate, it is due that the definition of <code>REMARK 0</code> was <strong>updated</strong> while <code>REMARK 6-99</code> are <em>are no longer for use of free text annotation</em>.</p>

<p>BTW, I am not sure how <a href="http://pdb-extract.wwpdb.org/" rel="nofollow noreferrer" title="Pdb_extract">Pdb_extract</a> would do with the remarks when converting the PDB file to CIF files. It would probably worth perusing  <a href="http://mmcif.wwpdb.org/docs/pdb_to_pdbx_correspondences.html#XPLOR" rel="nofollow noreferrer" title="PDB to PDBx/mmCIF Data Item Correspondences">PDB to PDBx/mmCIF Data Item Correspondences</a> page.</p>

CC BY-SA 3.0
2017-07-24T15:56:04.047Z
2017-07-26T23:01:09.873Z
2017-07-26T23:01:09.873Z
Mitra
<p><strong>Use any REMARK number not reserved for something else.</strong></p>

<p>The REMARK field was initially for general remarks. In the format description from 1992 only the numbers 1 to 3 were reserved for specific things, with the note:
<em>Other general commentary is given in higher numbered REMARKs</em>.</p>

<p>Then, in the next years, other remark numbers got reserved (and sometimes retired) for various specific annotations. The content of remarks was getting more and more formalized, to make it easier to parse by computers. The <a href="http://www.wwpdb.org/documentation/file-format" rel="nofollow noreferrer">specifications</a> from 1996 and 1998 recommended:</p>

<blockquote>
  <p>Non-standard remark annotations, or those with no clearly-defined
  topic or assigned remark number, appear with remark number 6 or
  greater, but less than remark number 100.</p>
</blockquote>

<p>I'd still follow this advice.
It is generally understood that when parsing PDB files one may have custom REMARK records.
I've seen also programs that output remarks without numbers - and this also doesn't cause problems with any reasonable PDB reader.
On the other hand, using remarks with numbers reserved for very specific things
(such as remark 250 in the most upvoted answer) can cause confusion.</p>

<p>The current spec (from 2012) is a precise description of files served by the wwPDB. It doesn't attempt to define a format for other uses, such as passing data between programs. In the section about <a href="https://www.wwpdb.org/documentation/file-format-content/format33/remarks1.html#REMARKs%206%20-%2099" rel="nofollow noreferrer">REMARKs 6-99</a> it has the last bullet point saying: "REMARKs 6-99 are no longer for use of free text annotation", because these remarks were removed from the old PDB entries. But it doesn't prevent from using it outside of the wwPDB.</p>

CC BY-SA 4.0
2020-03-30T17:29:18.263Z
2020-03-30T17:29:18.263Z
marcin
<p>From <a href="http://www.bmsc.washington.edu/CrystaLinks/man/pdb/part_31.html" rel="nofollow noreferrer">this document</a>, it looks like REMARK 250 is the way to go.</p>

CC BY-SA 3.0
2017-06-27T14:22:25.627Z
Great! I decided to use your answer https://github.com/mmagnus/rna-pdb-tools/commit/b11d33eba8e1311e89d98ba70e2eb087db878982
Marcin Magnus
CC BY-SA 4.0
2020-03-30T17:43:08.193Z
Why? This remark is reserved specifically for details of the experimental method (e.g.  powder diffraction) that the model is based on.
marcin
CC BY-SA 3.0
2017-06-25T22:03:05.130Z
2017-06-25T22:03:05.130Z
Dan
<p>I would like to add a text to PDB files that I'm processing with my tool, rna-pdb-tools. Someone points that the way I'm using it right now it's not correct (<a href="https://github.com/mmagnus/rna-pdb-tools/issues/48" rel="noreferrer">https://github.com/mmagnus/rna-pdb-tools/issues/48</a>).</p>

<p>I use HEADER right now which is not correct.</p>

<pre><code>HEADER Generated with rna-pdb-tools
HEADER ver 37c5b4e-dirty 
HEADER https://github.com/mmagnus/rna-pdb-tools 
HEADER Mon Oct 10 22:18:19 2016
ATOM      1  P     C A   1     -19.687  -3.296  65.469  1.00  0.00           P 
</code></pre>

<p>Do you happen to know which remark number to use? (<a href="http://www.wwpdb.org/documentation/file-format-content/format33/remarks1.html" rel="noreferrer">http://www.wwpdb.org/documentation/file-format-content/format33/remarks1.html</a>)?</p>

<file-formats><pdb>
PDB format: remark number for free text
# PDB format: remark number for free text

(Asked by: username_0 on 2017-06-23)

I would like to add a text to PDB files that I'm processing with my tool, rna-pdb-tools. Someone points that the way I'm using it right now it's not correct (https://github.com/mmagnus/rna-pdb-tools/issues/48).
I use HEADER right now which is not correct.
HEADER Generated with rna-pdb-tools
HEADER ver 37c5b4e-dirty 
HEADER https://github.com/mmagnus/rna-pdb-tools 
HEADER Mon Oct 10 22:18:19 2016
ATOM      1  P     C A   1     -19.687  -3.296  65.469  1.00  0.00           P 

Do you happen to know which remark number to use? (http://www.wwpdb.org/documentation/file-format-content/format33/remarks1.html)?

**Tags:** file-formats, pdb

---

## 3 answers

### Answer by username_3 on 2017-06-25. Score: 4 | Accepted answer

From [this document](http://www.bmsc.washington.edu/CrystaLinks/man/pdb/part_31.html), it looks like REMARK 250 is the way to go.

> **Comments:**
> **username_0**: Great! I decided to use your answer https://github.com/mmagnus/rna-pdb-tools/commit/b11d33eba8e1311e89d98ba70e2eb087db878982  
> **username_2**: Why? This remark is reserved specifically for details of the experimental method (e.g.  powder diffraction) that the model is based on.  

---

### Answer by username_1 on 2017-07-24. Score: 2

**EDIT:**

Actually, after having a more thorough look into the documentation; `REMARK 3` might be the more relevant to what you need. Other tools are reported in that section.

> REMARK 3 presents information on refinement program(s) used and related statistics. For non-diffraction studies, REMARK 3 is used to describe any refinement done, but its format is mostly free text.

[More on `Remark 3`](http://www.wwpdb.org/documentation/file-format-content/format33/remark3.html "More on `Remark 3`")

---

From the same source as you reference yourself [v 3.3](http://www.wwpdb.org/documentation/file-format-content/format33/remarks1.html "v 3.3"), I would argue that
`REMARK 0` would be more accurate than `REMARK 250`.

> REMARK 0 (updated), Re-refinement notice
> REMARK 0 identifies entries in which a re-refinement has been performed using the data from an existing entry. This remark also describes the PDB code and the journal records for the original data set.

While when you consider the definition of `REMARK 250`

-- which follows directly:

* `REMARK 205` (specific to Fiber diffraction experiment),
* `REMARK 201`(and `REMARK 215/217` all specific to NMR experiment),
* `REMARK 230` (neutron diffraction study),
* `REMARK 240`(electron crystallography study) and
* `REMARK 245`(and `REMARK 247`: specific to EM study)

> REMARK 250, Other Type of Experiment Details
>
> REMARKs specific to other kinds of studies, not listed above.
> REMARK 250 is mandatory if other than X-ray, NMR, neutron, or electron study. The format of the date in this remark is DD-MMM-YY. DD is the day of the month (a number 01 through 31), MMM is the English 3-letter abbreviation for the month, and YY is the year.

and then `REMARK 265` is also about the crystallography experiment.

Hence, I know that personally, I usually assume that whatever is annotated in `REMARK 250`is relevant to the first acquisition experiment to me.

Another reason I am more inclined to think `REMARK 0`is more accurate, it is due that the definition of `REMARK 0` was **updated** while `REMARK 6-99` are *are no longer for use of free text annotation*.

BTW, I am not sure how [Pdb\_extract](http://pdb-extract.wwpdb.org/ "Pdb_extract") would do with the remarks when converting the PDB file to CIF files. It would probably worth perusing [PDB to PDBx/mmCIF Data Item Correspondences](http://mmcif.wwpdb.org/docs/pdb_to_pdbx_correspondences.html#XPLOR "PDB to PDBx/mmCIF Data Item Correspondences") page.


---

### Answer by username_2 on 2020-03-30. Score: 1

**Use any REMARK number not reserved for something else.**

The REMARK field was initially for general remarks. In the format description from 1992 only the numbers 1 to 3 were reserved for specific things, with the note:
*Other general commentary is given in higher numbered REMARKs*.

Then, in the next years, other remark numbers got reserved (and sometimes retired) for various specific annotations. The content of remarks was getting more and more formalized, to make it easier to parse by computers. The [specifications](http://www.wwpdb.org/documentation/file-format) from 1996 and 1998 recommended:

> Non-standard remark annotations, or those with no clearly-defined
> topic or assigned remark number, appear with remark number 6 or
> greater, but less than remark number 100.

I'd still follow this advice.
It is generally understood that when parsing PDB files one may have custom REMARK records.
I've seen also programs that output remarks without numbers - and this also doesn't cause problems with any reasonable PDB reader.
On the other hand, using remarks with numbers reserved for very specific things
(such as remark 250 in the most upvoted answer) can cause confusion.

The current spec (from 2012) is a precise description of files served by the wwPDB. It doesn't attempt to define a format for other uses, such as passing data between programs. In the section about [REMARKs 6-99](https://www.wwpdb.org/documentation/file-format-content/format33/remarks1.html#REMARKs%206%20-%2099) it has the last bullet point saying: "REMARKs 6-99 are no longer for use of free text annotation", because these remarks were removed from the old PDB entries. But it doesn't prevent from using it outside of the wwPDB.


---

