Quickstart

Install the dnacurve package and all dependencies from the Python Package Index:

python -m pip install -U "dnacurve[all]"

Print the console script usage:

python -m dnacurve --help

Run the web application:

python -m dnacurve --web

See Examples and Documentation for using the programming interface.

Try the online calculator at https://www.cgohlke.com/dnacurve/.

Source code and support are available on GitHub.

Requirements

This revision was tested with the following requirements and dependencies (other versions may work):

• CPython 3.12.10, 3.13.17, 3.14.9, 3.15.1 64-bit

• Numpy 2.5.4

• Matplotlib 3.11.2

• Flask 3.1.3 (optional)

Revisions

2026.10.22

• Fix initializing Model from Model instance.

• Fix maxlen not enforced for Sequence instances in CurvedDNA.

• Fix comments in sequence files discarded.

• Fix main function ignoring argv argument.

• Fix command line returning exit code 0 on failure.

• Replace optparse with argparse.

• Add maxlen command line option.

• Add DNACURVE_MAXLEN environment variable to web application.

2026.8.15

• Add HTML application based on Pyodide.

2026.6.9

• Fix code review issues.

• Use HTML Living Standard in web application.

• Drop support for Python 3.11, support Python 3.15.

2026.1.8

• …

Refer to the CHANGES file for older revisions.

Notes

The algorithms, plots, and PDB format are not meant to be used with very long sequences. By default, sequences are truncated to 510 nucleotides, which can be overridden by the user.

The generated PDB files can be visualized interactively using UCSF Chimera.

Dnacurve.py was derived from DNACG.PAS (c) 1993, and DNACURVE.CPP (c) 1995.

References

1. Bending and curvature calculations in B-DNA. Goodsell DS, Dickerson RE. Nucleic Acids Res 22, 5497-503, 1994. See also http://mgl.scripps.edu/people/goodsell/research/bend/index.html.

2. Curved DNA without A-A: experimental estimation of all 16 DNA wedge angles. Bolshoy A et al. Proc Natl Acad Sci USA 88, 2312-6, 1991.

3. A comparison of six DNA bending models. Tan RK and Harvey SC. J Biomol Struct Dyn 5, 497-512, 1987.

4. Curved DNA: design, synthesis, and circularization. Ulanovsky L et al. Proc Natl Acad Sci USA 83, 862-6, 1986.

5. The ten helical twist angles of B-DNA. Kabsch W, Sander C, and Trifonov EN. Nucleic Acids Res 10, 1097-1104, 1982.

6. Rod models of DNA: sequence-dependent anisotropic elastic modelling of local bending phenomena. Munteanu MG et al. Trends Biochem Sci 23(9), 341-7, 1998.

Examples

>>> from dnacurve import CurvedDNA
>>> cdna = CurvedDNA('ATGCAAATTG' * 5, 'trifonov', name='Example')
>>> cdna.curvature[:, 18:22]
array([[0.58061616, 0.58163338, 0.58277938, 0.583783  ],
       [0.08029914, 0.11292516, 0.07675816, 0.03166286],
       [0.57923902, 0.57580064, 0.57367815, 0.57349872]])
>>> cdna.write_csv('_test.csv')
>>> cdna.write_pdb('_test.pdb')
>>> cdna.plot('_test.png', dpi=120)