# Error during parsing(Unsupported non-standard amino acid found: NAG )

**URL:** <https://ask.bioexcel.eu/t/error-during-parsing-unsupported-non-standard-amino-acid-found-nag/2423>\
**Category:** PRODIGY\
**Created:** [September 1, 2020, 2:25pm UTC](https://ask.bioexcel.eu/t/error-during-parsing-unsupported-non-standard-amino-acid-found-nag/2423 "2020-09-01T14:25:49Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Kashaf](https://avatars.discourse-cdn.com/v4/letter/k/f9ae1b/32.png) [@Kashaf](https://ask.bioexcel.eu/u/Kashaf)\
**Post date:** [September 1, 2020, 2:25pm UTC](https://ask.bioexcel.eu/t/error-during-parsing-unsupported-non-standard-amino-acid-found-nag/2423/1 "2020-09-01T14:25:49Z")

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Hello there!

I receive this error while trying to perform prodigy protein-protein on top pose structure obtained from HADDOCK.  
What should I do to remove this error?any recommendations for online servers that remove such errors from PDB file?

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<div class="post-metadata">

**Author:** ![amjjbonvin](https://dub1.discourse-cdn.com/flex013/user_avatar/ask.bioexcel.eu/amjjbonvin/32/23_2.png) [@amjjbonvin](https://ask.bioexcel.eu/u/amjjbonvin)\
**Post date:** [September 1, 2020, 5:45pm UTC](https://ask.bioexcel.eu/t/error-during-parsing-unsupported-non-standard-amino-acid-found-nag/2423/2 "2020-09-01T17:45:00Z")

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Such a web server is call a simple ASCII text editor to remove the lines containing NAG…

Or under Linux:

```
`grep -v NAG input.pdb >output.pdb`
```