[AMBER] Uasge of Nastruct command

From: Priyasha Majee via AMBER <amber.ambermd.org>
Date: Tue, 14 Apr 2026 16:36:27 +0530

Dear AMBER users and developers,

I want to calculate the standard helical, base-pair and base-step
parameters for my RNA-DNA hybrid duplex using nastruct command in
cpptraj. The script I am using is throwing errors:

parm sol-unmod.prmtop
trajin prod1000.nc 1 last 10
autoimage
nastruct MyAnalysis resrange 1-20\
sscalc\
naout dat\
out nastruct_summary.dat
run

The error is:

Error: [nastruct] Not all arguments handled: [ datout
nastruct_summary.dat ]
         1 errors encountered reading input.

I looked up for the correct script, but it's too complicated to
understand, and there's not much documentation. Please, can someone help
me with writing the basic script? Also, I have a modification in the DNA
strand. It's a base modification, so the numbering in the pyrimidine
ring is completely different from the natural nucleotides. Could you
tell me how to handle these cases? Which keyword should we use
specifically to address such modifications? I want to use nastruct for
both unmodified (wildtype) and modified duplexes. Could someone provide
a clean Nastruct script for the unmodified and modified duplex?

Thank you

Priyasha Majee
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Received on Tue Apr 14 2026 - 04:30:02 PDT
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