BackMapNet

BackMapNet is a deep-learning framework for reconstructing all-atom protein coordinates from coarse-grained (CG) trajectories.

Overview

BackMapNet performs local coordinate reconstruction with two coordinated models:

• A backbone model that predicts N, CA, C, O per residue.
• A side-chain model that predicts residue-specific heavy-atom coordinates in local frames.

This split improves transferability across proteins with different global folds and sequences.
The models were trained on 12 protein trajectories.

Pipeline Summary

BackMapNet is run through a single public entrypoint: BackMapNet.sh.

flowchart LR
  A["CG PDB frames"] --> B["Step 1: PDB -> cluster arrays"]
  B --> C["Step 2: Backbone inference + reverse scaling"]
  B --> D["Step 3: Side-chain local-frame inference"]
  C --> E["Step 4: Reconstruct combined array"]
  D --> E
  E --> F["Step 5: Optional PDB export"]
  G["AA PDB frames (optional)"] --> B

Loading

Tested Software Matrix

The repository does not currently include a lockfile; the matrix below reflects the active environment used for this project on March 17, 2026.

Profile	Conda env	Python	NumPy	TensorFlow	Keras	h5py	Intended use
Runtime	mytfenv311	3.11.15	2.4.2	2.20.0	3.13.1	3.16.0	BackMapNet pipeline execution

To print your exact runtime versions:

python3 - <<'PY'
import importlib, sys
print("python", sys.version.split()[0])
for name in ["numpy", "tensorflow", "keras", "h5py"]:
    try:
        mod = importlib.import_module(name)
        print(name, mod.__version__)
    except Exception:
        print(name, "MISSING")
PY

Installation

Create and activate an environment, then install core dependencies:

conda create -n backmapnet python=3.11 -y
conda activate backmapnet
pip install numpy tensorflow keras h5py

Repository Layout

Top-level structure:

• BackMapNet.sh: public pipeline entrypoint.
• run_all.sh: backward-compatible wrapper that forwards to BackMapNet.sh.
• bash_scripts/: stage-level shell workflows.
• python_scripts/: array builders, model evaluation, reconstruction, and PDB writing.
• weights/: backbone/side-chain model files and priors.

Input Conventions

BackMapNet expects frame-indexed PDB filenames:

• CG directory (--cg-pdb-dir): CG_frame_<idx>.pdb
• Backbone AA directory (--aa-pdb-dir, optional): frame_<idx>.pdb
• Side-chain AA directory (--aa-sc-pdb-dir, required when full side-chain mode is used): frame_<idx>_SC.pdb

If --aa-pdb-dir is provided, BackMapNet automatically switches from CG-only mode to full mode.

Running BackMapNet

Show CLI help:

bash /absolute/path/to/backbone/BackMapNet.sh --help

CG-only mode (default)

bash /absolute/path/to/backbone/BackMapNet.sh \
  --pdb-name IgE \
  --cg-pdb-dir /data/IgE/cg \
  --jobs 8

Full mode (backbone + side-chain targets) Evaluation

bash /absolute/path/to/backbone/BackMapNet.sh \
  --pdb-name IgE \
  --cg-pdb-dir /data/IgE/cg \
  --aa-pdb-dir /data/IgE/aa_backbone \
  --aa-sc-pdb-dir /data/IgE/aa_sidechain \
  --jobs 8

Optional PDB export

bash /absolute/path/to/backbone/BackMapNet.sh \
  --pdb-name IgE \
  --cg-pdb-dir /data/IgE/cg \
  --write-pdb 1 \
  --pdb-frame-spec all

Output Files

Typical outputs are generated in the run directory:

• backbone_<PDB>_prediction.npy
• backbone_<PDB>_actual.npy (full mode only)
• sidechain_<PDB>_prediction.npy
• combined_<PDB>_prediction.npy (CG-only)
• combined_<PDB>_actual.npy (full mode)
• pdb_frames_<PDB>/ (when --write-pdb 1)

Atomic Mapping Specification

This section defines the atom ordering used by reconstruction and PDB writing.

Backbone mapping

Per residue:

CG feature	Reconstructed atoms	Atom order
BB bead	Backbone heavy atoms	N, CA, C, O

Side-chain mapping

Per residue, side-chain heavy atoms are produced in this fixed order:

Residue	Side-chain atom order
ALA	CB
ARG	CB, CG, CD, NE, CZ, NH1, NH2
ASN	CB, CG, OD1, ND2
ASP	CB, CG, OD1, OD2
CYS	CB, SG
GLN	CB, CG, CD, OE1, NE2
GLU	CB, CG, CD, OE1, OE2
GLY	(no side-chain atoms)
HIS	CB, CG, ND1, CE1, NE2, CD2
ILE	CB, CG2, CG1, CD
LEU	CB, CG, CD1, CD2
LYS	CB, CG, CD, CE, NZ
MET	CB, CG, SD, CE
PHE	CB, CG, CD1, CE1, CZ, CE2, CD2
PRO	CD, CG, CB
SER	CB, OG
THR	CB, CG2, OG1
TRP	CB, CG, CD1, NE1, CE2, CZ2, CH2, CZ3, CE3, CD2
TYR	CB, CG, CD1, CE1, CZ, OH, CE2, CD2
VAL	CB, CG1, CG2

Final merged array order

In combined_<PDB>_*.npy, each residue is assembled as:

1. Backbone atoms: N, CA, C, O
2. Side-chain atoms: residue-specific order from the table above

Notes

• Use BackMapNet.sh as the public interface. Internal scripts are implementation details and may change.
• For publication reproducibility, record your exact environment with the version probe command above.