> ## Documentation Index > Fetch the complete documentation index at: https://proto.evodesign.org/docs/llms.txt > Use this file to discover all available pages before exploring further. # Gyration Radius > Filter structures by radius of gyration (compactness)

**License:** Structure Metrics is open source and free for academic and commercial use under an MIT license. Please refer to [the license](https://github.com/evo-design/proto-tools) for full terms.

This constraint is open source. Any third-party models, product names, or trademarks referenced are the property of their respective owners, and Proto is not affiliated with them.

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evo-design/proto-language/proto\_language/constraint/protein\_structure/gyration\_radius\_constraint.py

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```bibtex theme={null} @article{kunzmann2023biotite, title={Biotite: new tools for a versatile {Python} bioinformatics library}, author={Kunzmann, Patrick and M{\"u}ller, Tom David and Greil, Maximilian and Krumbach, Jan Hendrik and Anter, Jacob Marcel and Bauer, Daniel and Islam, Faisal and Hamacher, Kay}, journal={BMC Bioinformatics}, volume={24}, number={1}, pages={236}, year={2023}, publisher={BioMed Central}, doi={10.1186/s12859-023-05345-6} } @article{labesse1997psea, title={{P-SEA}: a new efficient assignment of secondary structure from {C}$\alpha$ trace of proteins}, author={Labesse, Gilles and Colloc'h, Nathalie and Pothier, Joel and Mornon, Jean-Paul}, journal={Bioinformatics}, volume={13}, number={3}, pages={291--295}, year={1997}, publisher={Oxford University Press}, doi={10.1093/bioinformatics/13.3.291} } ```

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Filter structures by radius of gyration. ## API Reference

ConfigGyrationRadiusConfig Source

Configuration for gyration radius constraint. Maximum acceptable radius of gyration in Ångströms (lower values are more compact).

ReturnsConstraintOutput

Per-proposal score in `[0.0, 1.0]` with `gyration_radius` and `longest_alpha_helix` metadata. Sequences without a structure receive `MAX_ENERGY` and no metadata.

## Usage ```python python icon="python" theme={null} from proto_language.core import Constraint from proto_language.constraint import gyration_radius_constraint, GyrationRadiusConfig constraint = Constraint( inputs=[segment], function=gyration_radius_constraint, function_config=GyrationRadiusConfig( # Configure parameters here ), ) scores = constraint.evaluate() ``` ## Metadata | Property | Value | | --------------- | ---------------------------- | | Key | `gyration-radius` | | Function | `gyration_radius_constraint` | | Category | `protein_structure` | | Mode | `discrete` | | Uses GPU | `False` | | Supported Types | `protein`, `dna` |