btwisted takes a region of a pure DNA sequence and calculates by simple arithmetic the probable overall twist of the sequence and the stacking energy.

Here is a sample session with btwisted:

% btwisted embl:ab000095 -sbegin 100 -send 120
Calculates the twisting in a B-DNA sequence
Output file [ab000095.btwisted]:

Mandatory qualifiers:

[-sequence] (sequence)

Sequence USA.

[-outfile] (outfile)

Output filename.

Advanced qualifiers:

-angledata (string)

File containing base pair twist angles.

-energydata (string)

File containing base pair stacking energies.