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Dear Dr. Xiang,

I was analyzing the base pair type distribution among a dataset of RNAs that I have collected for my study using the pair.csv file for those PDB IDs obtained using web-3DNA. When I compiled the list of unique base pair types I noticed certain base pairs with a P, which are: P+A, A-P, P-G, P+G, C-P and P-A.
I got information on the other base pair types from the x3DNA website:, but I'm unable to find information on the above mentioned base pairs. Can you share some resources to understand what these named base pairs mean and how they are identified (in terms of the structural orientation of the bases and other parameters)?

Thank you
- Sowmya
FAQs / Re: Where to download x3DNA
« Last post by sahithjayceion on November 09, 2022, 12:55:46 am »
I waited after registration but still cannot view the download section. It would be great if you could give me access! regards.

An Error Has Occurred!
The topic or board you are looking for appears to be either missing or off limits to you.
w3DNA -- web interface to 3DNA / can't open the baselist file error for 2 PDB IDs
« Last post by sowmya on October 19, 2022, 07:54:02 am »
Dear Dr. Xiang,

I was trying to calculate the base pair and base step parameters for PDB IDs - 7E9E and 7E9I by uploading the PDB files to the web interface of 3DNA. I am getting a "can't open the baselist file error" for these 2 IDs. I am yet to come across this error for other PDB IDs - I have calculated for around 20 other PDB IDs (deposited after 2019) in the web interface and they were parsed fine. Requesting your suggestions to resolve this error in the web interface.

With regards,
Hi Andrea,

DSSR Pro can do what you want very easily, especially in combination with the --json option. See No more grant funding for 3DNA/DSSR.

Base atoms have always been necessary for the identification of nucleotides in order to calculate base-pair and backbone parameters in 3DNA v2.x, including the command you mentioned: analyze -t=torsions.out. However, since 3DNA v2.x is open source for academic uses, you can modify it to meet your needs.

Best regards,

Dear Dr. Xiang-Jun Lu,

I used versions of 3DNA earlier than the 2018 versions some time ago, in those versions it was possible to calculate the torsion angles of the sugar-phosphate backbone of DNA, without taking into account the bases, with the following command:

analyze -t = name.tor name.pdb

However in the new versions, this task is not possible anymore, it is necessary to have the nitrogenous bases or at least   N1, C2 or N9, C4 atoms. 

I was wondering if there is a new instruction or way to do that, because it would shorten my work route considerably. One of my study purposes is the optimized fragments of the Sugar-Phosphate Backbone, in these fragments the nitrogenous bases of the DNA are eliminated and replaced by a hydrogen (position N1 or N9) as shown in file attached .

Thank you very much,

Andrea R.

Site announcements / Re: Clarification on DSSR licensing
« Last post by xiangjun on August 11, 2022, 09:24:51 am »
Hi Dr. Baulin,

is it safe to freely use the old DSSR version for academic use according to the old license?

Yes. Keep in mind that such outdated versions are no longer supported or maintained.

Best regards,

Site announcements / Re: Clarification on DSSR licensing
« Last post by febos on August 11, 2022, 07:34:37 am »
Hi Dr. Lu!

About two years ago I downloaded DSSR version 2.0 for academic use and since then I built some work using the tool. Only now have I found out that the newest DSSR versions are not freely available anymore. And now I have a question - is it safe to freely use the old DSSR version for academic use according to the old license?

Thank you!

Best regards,
Eugene Baulin
Hi Xiangjun:
     When we use 3DNA to analyze the tertiary structure of RNA, we get the local base pair parameters and simple base pair parameters, and know that different base-pair coordinate frames lead to different results. We would like to know what is the relationship between the two base-pair coordinate frames, but we have not found anything after searching. Could you help us solve this problem?

Site announcements / Re: Download instructions
« Last post by wdz-victor on March 25, 2022, 01:09:21 am »
Hello everyone, how can I get the old version of the program, or how can the new version 2.4 program run through the pymol script. (No x3dna-dssr.exe found in the new program)
General discussions (Q&As) / Rebuild with backbone from single-stranded .par file
« Last post by nicalleb on March 21, 2022, 07:39:35 am »

I would like to rebuild a stacked nucleobases structure from a .par file (with the 6  base-step parameters, see in attachment). This .par file was obtained by analyzing a single-stranded GTT stack (PDB file) with the command "find pair". If I rebuild my structure from this .par file with the following command :

rebuild -atomic bp_step.par test_rebuild.pdb

I get a structure without backbone and I need the backbone in subsequent calculations.

With the "Rebuilding" module of the online version of X3DNA, I know it is possible to have a structure with backbone, even starting with a .par file for a single-strand (containing only 6 local base-step parameters)

Is it also possible in command line (with the downloaded version of the software) and if so, how ?

Thank you in advance,

Nicolas Callebaut
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Created and maintained by Dr. Xiang-Jun Lu [律祥俊] (
The Bussemaker Laboratory at the Department of Biological Sciences, Columbia University.