# Bio Files: Read and write common biology file formats
[](https://crates.io/crates/bio_files)
[](https://docs.rs/bio_files)
[](https://pypi.org/project/biology-files)
[](https://doi.org/10.5281/zenodo.17445294)
[Home page](https://www.athanorlab.com/rust-tools)
This Rust and Python library contains functionality to load and save data in common biology file formats. It operates
on data structures that are specific to each file format; you will need to convert to and from the structures
used by your application. The API docs, and examples below are sufficient to get started.
Note: Install the pip version with `pip install biology-files` due to a name conflict.
### Supported formats:
- mmCIF (Protein atom, residue, chain, and related data like secondary structure)
- mmCIF (structure factors / 2fo-fc: Electron density data, raw)
- Mol2 (Small molecules, e.g. ligands)
- SDF (Small molecules, e.g. ligands)
- XYZ (Minimal atom coordinate format. Used by ORCA.)
- PDBQT (Small molecules, e.g. ligands. Includes docking-specific fields.)
- Map (Electron density, e.g. from crystallography, Cryo EM. Processed using Fourier transforms)
- MTZ: If [Gemmi](https://gemmi.readthedocs.io/en/latest/) is installed. (Electron density)
- AB1 (Sequence tracing)
- DAT (Amber force field data for small molecules)
- FRCMOD (Amber force field patch data for small molecules)
- Amber .lib files, e.g. with charge data for amino acids and proteins.
- GRO (GROMACS molecules)
- TOP (GROMACS topology)
- MDP (GROMACS MD configuration)
- EDR (GROMACS energy output)
- ORCA input and output files (quantum chemistry; HF, DFT etc)
- TRR (MD trajectories)
- XTC: If [MDTraj](https://www.mdtraj.org/1.9.8.dev0/index.html) is installed. (MD trajectories, compressed)
DCD (MD trajectories)
### Planned:
- DNA (Exists in PlasCAD; needs to be decoupled)
## Generic data types
This library includes a number of relatively generic data types which are returned by various load functions,
and required to save data. These may be used in your application directly, or converted into a more specific
format. Examples:
- [AtomGeneric](https://docs.rs/bio_files/latest/bio_files/struct.AtomGeneric.html)
- [BondGeneric](https://docs.rs/bio_files/latest/bio_files/struct.BondGeneric.html)
- [ResidueGeneric](https://docs.rs/bio_files/latest/bio_files/struct.ResidueGeneric.html)
- [BondType](https://docs.rs/bio_files/latest/bio_files/enum.BondType.html)
- [LipidStandard](https://docs.rs/bio_files/latest/bio_files/enum.LipidStandard.html)
For Genbank, we recommend [gb-io](https://docs.rs/gb-io/latest/gb_io/). We do not plan to support this format, due to
this high quality library.
Each module represents a file format, and most have dedicated structs dedicated to operating on that format.
It operates using structs with public fields, which you can explore
using the [API docs](https://docs.rs/bio_files), or your IDE. These structs generally include these three methods:
`new()`,
`save()` and `load()`. `new()` accepts `&str` for text files, and a `R: Read + Seek` for binary. `save()` and
`load()` accept `&Path`.
The Force Field formats use `load_dat`, `save_frcmod` instead, as they use the same structs for both formats.
## Serial numbers
Serial numbers for atoms, residues, secondary structure, and chains are generally pulled directly from atom data files
(mmCIF, Mol2 etc). These lists reference atoms, or residues, stored as `Vec<u32>`, with the `u32` being the serial
number.
In your application, you may wish to adapt these generic types to custom ones that use index lookups
instead of serial numbers. We use SNs here because they're more robust, and match the input files directly;
add optimizations downstream, like converting to indices, and/or applying back-references. (e.g. the index of the
residue
an atom's in, in your derived Atom struct).
## ORCA interface
This library provides an interface to build Orca inputs, execute commands, and parse outputs. It uses Rust
datastructures to contrain input choices into valid ones when possible, and allows you to integrate Orca into Rust
programs and libraries. For example, [Molchanica](https://github.com/david-oconnor/molchanica) uses it to minimize
energy on organic molecules, and augment traditional MD technique with quantum mechanics. See
the [API docs](https://docs.rs/bio_files/latest/bio_files/orca/index.html) for details.
ORCA support in this library is limited to Rust only. If you wish to use Orca with Python,
use [OPI, the official FACCTS library](https://github.com/faccts/opi).
Note: Orca support is currently limited to a subset of features. We plan to gradually expand this. If you're looking for
specific functionality, please open an Issue or PR on Github.
Can generate and run [ORCA](https://www.faccts.de/orca/) commands, and parse the result. Example:
(todo )
## GROMACS interface
This library provides an interface to build [GROMACS](https://www.gromacs.org/) inputs, run MD, and parse outputs. This
is similar conceptually to the ORCA interface. We use it in [Molchanica](https://github.com/david-oconnor/molchanica) as
an optional backend for MD. See the [API docs](https://docs.rs/bio_files/latest/bio_files/gromacs/index.html). To use
it, GROMACS must be installed, and available on the system path.
It constructs an [MDP](https://manual.gromacs.org/current/user-guide/mdp-options.html) configuration, converts
molecules (From atoms and bonds) into a .gro files, and creates a topology from force field parameters. It launches
`grompp` and `gmx` to prepare and run MD. Once complete, it collects data from the files GROMACS generates: `.trr` for
trajectory data, `.edr` for thermodynamic properties, and `.log` for general information.
We do not provide Python bindings to this functionality, as it's handled by
the [official gmxapi library](https://manual.gromacs.org/current/gmxapi/userguide/usage.html).
It also offers standalone functionality to read and write TRR and other files.
Minimal example:
```rust
use bio_files::{
gromacs::{GromacsInput, MdpParams, OutputControl, MoleculeInput},
ForceFieldParams,
};
fn run_gromacs() -> io::Result<()> {
let mols = ();
// The default implementation for each field will use GROMACS defaults; override
// ones we wish to change.
let mdp = MdpParams {
integrator: Integrator::MdVv,
nsteps: 1_000,
dt: 0.001,
output_control: OutputControl {
txout: Some(100),
nstenergy: Some(500),
..Default::default()
}
..Default::default()
};
let molecules = {
let mol = Sdf::load_pubchem(2244)?;
// todo: Demonstrate how to load mol specific params, e.g. with antechamber
vec![MoleculeInput {
name: &mol.ident,
atoms: mol.atoms.clone(),
bonds: mol.bonds.clone(),
// ff_params: Some(ff_params_mol_specific),
ff_params: None,
count: 0,
}]
};
let p = Path::new("gaff2.dat");
let params = ForceFieldParams::load_dat(p)?;
let input = GromacsInput {
mdp,
molecules,
box_nm: Some((30., 30., 30.)),
ff_global: Some(params),
water_model,
};
let output = input.run()?;
println!("Gromacs output log: \n\n{}", output.log_text);
for frame in &output.trajectory {
println!("Frame time: {:?.3}", frame.time);
println!("Energy: {:?}", frame.energy);
// Do something with `frame.atom_posits` and `frame.atom_velocities` as required.
}
}
```
## Loading building-block molecules from templates
We can load amino acids, nucleic acids, and lipids from Amber template files. These are standard
molecule segments used to build common biological molecules. Example usage:
```rust
use dynamics::{LIPID_21_LIB, AMINO_19, RNA_LIB, OL24_LIB};
// Returns io::Result<HashMap<String, TemplateData>>
let lipids = load_templates(LIPID_21_LIB).unwrap();
let dna = load_templates(OL24_LIB).unwrap();
let amino_acids = load_templates(AMINIO19_LIB).unwrap();
```
## Code examples
```rust
use std::path::PathBuf;
use bio_files::orca::{OrcaInput, Thermostat, Method, Task, BasisSet};
fn main() {
let mut orca_inp = OrcaInput {
task:
method: Method::PBE0,
basis_set: BasisSet::Def2Svp,
atoms,
..Default::default()
};
orca_inp.keywords = vec![Keyword::D4Dispersion];
println!("Orca input:\n{}\n", orca_inp.make_inp());
// Save to disk if desired:
orca_inp.save(Path::new("atoms.inp"))?;
println!("Running Orca...");
let orca_out = orca_inp.run().unwrap();
println!("Orca OUT:\n{:?}\n", orca_out);
// To run an ab-initio dynamics sim:
let dyn = Dynamics {
timestep: 0.5,
init_vel: 310.,
thermostat: Thermostat::Csvr,
thermostat_temp: 310.,
thermostat_timecon: 10.,
traj_out_dir: PathBuf::from_str(
"traj.xyz").unwrap(),
steps: 200,
};
let orca_inp = OrcaInput {
task: Task::Dynamics(dyn),
method: Method::R2SCAN_c3,
basis_set: BasisSet::Tzvp,
atoms,
..Default::default()
};
orca_inp.run().unwrap();
}
```
## Example use
Small molecule save and load, Python.
```python
from biology_files import Sdf
sdf_data = Sdf.load("./molecules/DB03496.sdf")
sdf_data.atoms[0]
#AtomGeneric { serial_number: 1, posit: Vec3 { x: 2.3974, y: 1.1259, z: 2.5289 }, element: Chlorine,
type_in_res: None, force_field_type: None, occupancy: None, partial_charge: None, hetero: true }
sdf_data.atoms[0].posit
# [2.3974, 1.1259, 2.5289]
sdf_data.save("test.sdf")
mol2_data = sdf_data.to_mol2()
mol2_data.save("test.mol2")
# Load molecules from databases using identifiers:
mol = Sdf.load_drugbank("DB00198")
mol = Sdf.load_pubchem(12345)
mol = Sdf.load_pdbe("CPB")
mol = Mol2.load_amber_geostd("CPB")
peptide = MmCif.load_rcsb("8S6P")
# (See the Rust examples and API docs for more functionality; most
# is exposed in Python as well)
```
Small molecule save and load, Rust.
```rust
use bio_files::{Sdf, SdfFormat, Mol2};
// ...
let sdf_data = Sdf::load(Path::new("./molecules/DB03496.sdf")) ?;
sdf_data.atoms[0]; // (as above)
sdf_data.atoms[0].posit; // (as above, but lin_alg::Vec3))
sdf_data.save(Path::new("test.sdf"), SdfFormat::V2000) ?;
let mol2_data: Mol2 = sdf_data.into();
mol2_data.save(Path::new("test.mol2")) ?;
let xyz_data = Xyz::load(Path::new("./atom_posits.xyz")) ?;
// Loading Force field parameters:
let p = Path::new("gaff2.dat")
let params = ForceFieldParams::load_dat(p) ?;
// Load electron density structure factors data, to be processed with a FFT:
let path = Path::new("8s6p_validation_2fo-fc_map_coef.cif");
let data = CifStructureFactors::new_from_path(path) ?;
// These functions aren't included; an example of turning loaded structure factor data
// into a density map.
let mut fft_planner = FftPlanner::new();
let dm = density_map_from_mmcif( & data, & mut fft_planner) ?;
// Or if you have a Map file:
let p = Path::new("8s6p.map");
let dm = DensityMap::load(path) ?;
// For MTZ files, or 2fo-fc:
let dm = DensityMap::from_sf_or_mtz(path, None) ?;
// Saving a density map:
dm.save(Path::new("8s6p.map")) ?;
// Uses the file extension `.mmcif` or `.mtz` to determine which format to save as.
dm.save_sf_or_mtz(Path::new("8s6p.mtz")) ?;
// Load molecules from databases using identifiers:
let mol = Sdf::load_drugbank("DB00198") ?;
let mol = Sdf::load_pubchem(12345) ?;
let mol = Sdf::load_pdbe("CPB") ?;
let mol = Mol2::load_amber_geostd("CPB") ?;
let peptide = MmCif::load_rcsb("8S6P") ?;
```
You can use similar syntax for mmCIF protein files.
## Amber force fields
Reference the [Amber 2025 Reference Manual, section 15](https://ambermd.org/doc12/Amber25.pdf)
for details on how we parse its files, and how to use the results. In some cases, we change the format from
the raw Amber data. For example, we store angles as radians (vice degrees), and σ vice R_min for Van der Waals
parameters. Structs and fields are documented with reference manual references.
The Amber forcefield parameter format has fields which each contain a `Vec` of a certain type of data. (Bond stretching
parameters,
angle between 3 atoms, torsion/dihedral angles etc.) You may wish to parse these into a format that has faster lookups
for your application.
Note that the above examples expect that your application has a struct representing the molecule that has
`From<Mol2>`, and `to_mol2(&self)` (etc) methods. The details of these depend on the application. For example:
```rust
impl From<Sdf> for Molecule {
fn from(m: Sdf) -> Self {
// We've implemented `From<AtomGeneric>` and `From<ResidueGeneric>` for our application's `Atom` and
// `Residue`
let atoms = m.atoms.iter().map(|a| a.into()).collect();
let residues = m.residues.iter().map(|r| r.into()).collect();
Self::new(m.ident, atoms, m.chains.clone(), residues, None, None);
}
}
```
A practical example of parsing a molecule from a `mmCIF` as parsed from `bio_files` into an application-specific format:
```rust
fn load() {
let cif_data = mmcif::load("./1htm.cif");
let mol: Molecule = cif_data.try_into().unwrap();
}
impl TryFrom<MmCif> for Molecule {
type Error = io::Error;
fn try_from(m: MmCif) -> Result<Self, Self::Error> {
let mut atoms: Vec<_> = m.atoms.iter().map(|a| a.into()).collect();
let mut residues = Vec::with_capacity(m.residues.len());
for res in &m.residues {
residues.push(Residue::from_generic(res, &atoms)?);
}
let mut chains = Vec::with_capacity(m.chains.len());
for c in &m.chains {
chains.push(Chain::from_generic(c, &atoms, &residues)?);
}
// Now that chains and residues are loaded, update atoms with their back-ref index.
for atom in &mut atoms {
for (i, res) in residues.iter().enumerate() {
if res.atom_sns.contains(&atom.serial_number) {
atom.residue = Some(i);
break;
}
}
for (i, chain) in chains.iter().enumerate() {
if chain.atom_sns.contains(&atom.serial_number) {
atom.chain = Some(i);
break;
}
}
}
let mut result = Self::new(m.ident.clone(), atoms, chains, residues, None, None);
result.experimental_method = m.experimental_method.clone();
result.secondary_structure = m.secondary_structure.clone();
result.bonds_hydrogen = Vec::new();
result.adjacency_list = result.build_adjacency_list();
Ok(result)
}
}
```
# A protein loading and prep example:
Python:
```python
use biology_files::{Mol2, MmCif, ForceFieldParams, FfParamSet, prepare_peptide, load_prmtop};
mol = Mol2.load("CPB.mol2")
protein = MmCif.load("1c8k.cif")
param_set = FfParamSet.new_amber()
lig_specific = ForceFieldParams.load_frcmod("CPB.frcmod")
# Or, instead of loading atoms and mol-specific params separately:
# mol, lig_specific = load_prmtop("my_mol.prmtop")
# Add Hydrogens, force field type, and partial charge to atoms in the protein; these usually aren't
# included from RSCB PDB. You can also call `populate_hydrogens_dihedrals()`, and
# `populate_peptide_ff_and_q() separately. Add bonds.
protein.atoms, protein.bonds = prepare_peptide(
protein.atoms,
protein.bonds,
protein.residues,
protein.chains,
param_set.peptide_ff_q_map,
7.0,
)
```
Rust:
```rust
use bio_files::{MmCif, Mol2, ForceFieldParams, FfParamSet, prepare_peptide, load_prmtop};
use std::path::Path;
fn load() {
let param_set = FfParamSet::new_amber().unwrap();
let mut protein = MmCif::load(Path::new("1c8k.cif")).unwrap();
let mol = Mol2::load(Path::new("CPB.mol2")).unwrap();
let mol_specific = ForceFieldParams::load_frcmod(Path::new("CPB.frcmod")).unwrap();
// Or, instead of loading atoms and mol-specific params separately:
// let (mol, lig_specific) = load_prmtop("my_mol.prmtop");
// Or, if you have a small molecule available in Amber Geostd, load it remotely:
// let data = bio_apis::amber_geostd::load_mol_files("CPB");
// let mol = Mol2::new(&data.mol2);
// let mol_specific = ForceFieldParams::from_frcmod(&data.frcmod);
// Add Hydrogens, force field type, and partial charge to atoms in the protein; these usually aren't
// included from RSCB PDB. You can also call `populate_hydrogens_dihedrals()`, and
// `populate_peptide_ff_and_q() separately. Add bonds.
prepare_peptide(
&mut protein.atoms,
&mut protein.bonds,
&mut protein.residues,
&mut protein.chains,
¶m_set.peptide_ff_q_map.as_ref().unwrap(),
7.0,
)
.unwrap();
}
```
## MD trajectories example
```rust
use bio_files::dcd::DcdTrajectory;
fn main() {
let path_dcd = Path::new("traj.dcd");
let path_xtc = Path::new("traj.xtc.rs");
// Or TRR
// Load trajectory files:
let traj = DcdTrajectory::load(path_dcd).unwrap();
// Or, if you have MDTraj installed, load XTC files:
let traj = DcdTrajectory::load_xtc(path_xtc).unwrap();
for frame in &traj.frames {
println!("Time: {} unit cell: {:?}", frame.time, frame.unit_cell);
println!("Positions:");
for posit in &frame.atom_posits {
// ...
}
}
// To save:
traj.save(path_dcd).unwrap();
traj.save_xtc(path_xtc).unwrap();
}
```
Note: The Python version is currently missing support for some formats, and not all fields are exposed.
### References
- [Amber 2025 Reference Manual, section 15](https://ambermd.org/doc12/Amber25.pdf)