BioMatrix-4B-Base

BioMatrix is a multimodal biological foundation model that natively integrates 1D sequences, 3D structures, and natural language for both molecules and proteins within a single decoder-only architecture.

This is the 4B-parameter Base model, obtained via multimodal continual pretraining of Qwen3-4B-Base on 304.4 billion tokens spanning text, molecular and protein 1D/3D data, and cross-modal corpora. This base checkpoint is intended for further fine-tuning on downstream tasks. For an instruction-tuned model ready for inference, see BioMatrix-4B-SFT.

Model Overview

BioMatrix maps all biological modalities into a shared discrete token space via a unified tokenization scheme:

  • Molecular 1D sequences (both SMILES and SELFIES notations)
  • Molecular 3D structures (via MolStrucTok with branch-decoupled decoder)
  • Protein 1D sequences (residue-level tokens)
  • Protein 3D structures (via GCP-VQVAE backbone tokenizer)
  • Natural language (inherited from Qwen3 tokenizer)

All modalities are consumed and produced uniformly under a single next-token prediction objective—without external encoders, projection adapters, or modality-specific output heads.

Model Molecule 1D Molecule 3D Protein 1D Protein 3D Natural Language
ESM3
3D-MoLM
AlphaFold3
BioT5/BioT5+
BioMedGPT
BioMatrix

Model Details

  • Base Architecture: Qwen3-4B-Base
  • Parameters: 4B
  • Training Stage: Multimodal Continual Pretraining only (not instruction-tuned)
  • Training Tokens: 304.4B
  • Context Length: 8,192 tokens
  • Tokenizer: Extended Qwen3 vocabulary with:
    • 11,294 joint molecular 3D tokens (composed from SELFIES atom × MolStrucTok codes)
    • 4,096 protein 3D tokens (GCP-VQVAE codebook)
    • 26 protein 1D tokens (amino acids + non-standard/unknown)
    • SELFIES atom tokens and modality-specific control tokens

Embedding Initialization

New vocabulary entries are initialized via a description-based scheme: each new token is grounded in the pretrained Qwen3 embedding space by averaging the embeddings of the subword tokens of a short natural-language description (e.g., <A_W> → "Tryptophan"), plus a small isotropic Gaussian perturbation to break symmetry. This provides a more stable starting point than random initialization.

Pretraining Corpus (304.4B tokens)

Category Tokens Sources
Text (105.3B) General: 25.6B FineWeb-Edu
Scientific: 79.7B FineFineWeb (biology/chemistry/medical/health), PubMed Full Articles
Molecule (73.7B) 1D: 36.0B PubChem, MolTextNet
3D: 17.6B PubChem, PCQM4Mv2, PubChemQC
Other: 24.0B (text descriptions, properties, IUPAC names)
Protein (77.4B) 1D: 17.1B UniRef50
3D: 38.5B RCSB PDB, AlphaFold DB
Other: 19.5B Swiss-Prot, TrEMBL annotations
Other (additional): 2.9B
Cross-entity (48.0B) Interleaved Text: 17.1B PubMed, bioRxiv, S2ORC, USPTO
3D: 11.4B CrossDocked, PPIRef
Other: 19.5B BindingDB, STITCH, jglaser, AlphaSeq

Training Configuration

  • Framework: LLaMA-Factory
  • Hardware: 64 NVIDIA H100 GPUs
  • Global Batch Size: 1,024
  • Maximum Sequence Length: 8,192 tokens
  • Optimizer: AdamW
  • Peak Learning Rate: 2.0 × 10⁻⁴ (cosine schedule)
  • Warmup Steps: 2,000
  • Total Steps: ~36.4K (1 epoch over the full 304.4B-token corpus)

Intended Use

This Base model is not instruction-tuned. It is suitable for:

  • Further fine-tuning on custom biological tasks
  • Continued pretraining on domain-specific corpora
  • Research on representation learning across biomolecular modalities
  • Embedding extraction for downstream classification/regression tasks

For ready-to-use instruction-following capabilities (e.g., molecule captioning, protein design, property prediction), please use the SFT variant.

Quick Start

from transformers import AutoModelForCausalLM, AutoTokenizer

model_name = "QizhiPei/BioMatrix-4B-Base"
tokenizer = AutoTokenizer.from_pretrained(model_name, trust_remote_code=True)
model = AutoModelForCausalLM.from_pretrained(
    model_name,
    torch_dtype="auto",
    device_map="auto",
    trust_remote_code=True
)

# Example: Continue a SMILES sequence
prompt = "<|mol_smi_start|>CC(=O)"
inputs = tokenizer(prompt, return_tensors="pt").to(model.device)
outputs = model.generate(**inputs, max_new_tokens=512)
print(tokenizer.decode(outputs[0], skip_special_tokens=False))

Modality Wrapping

When constructing inputs, biomolecular content must be wrapped with the corresponding control tokens:

Modality Wrapping Example
Molecule SMILES <|mol_smi_start|>CC#CC#N<|mol_smi_end|>
Molecule SELFIES <|mol_sfi_start|>[C][#C][C][#N]<|mol_sfi_end|>
Molecule 3D <|mol_3d_start|>[H 3][C 0][#C 6]...<|mol_3d_end|>
Protein 1D <|prot_aa_start|><A M><A R><A A>...<|prot_aa_end|>
Protein 3D <|prot_3d_start|><S 4012><S 153><S 2091>...<|prot_3d_end|>

Natural language text is left unwrapped and serves as the default carrier modality.

Limitations

  • This model is not instruction-tuned and is unlikely to follow natural-language instructions out-of-the-box. Use the SFT variant for instruction-following.
  • Molecular and protein 3D structures are tokenized in disjoint geometric reference frames, so the model cannot natively represent biomolecular complexes (e.g., docking poses).
  • Heavy domain specialization may erode some general-purpose language capabilities of the underlying Qwen3 backbone.
  • Coverage is limited to small molecules and proteins; nucleic acids, carbohydrates, and lipids are not currently supported.

Citation

If you find BioMatrix useful, please cite:

@article{pei2026biomatrix,
  title={BioMatrix: Towards a Comprehensive Biological Foundation Model Spanning the Modality Matrix of Sequences, Structures, and Language},
  author={Pei, Qizhi and Zhou, Zhimeng and Duan, Yi and Zhao, Yiyang and He, Liang and Hsieh, Chang-Yu and He, Conghui and Yan, Rui and Wu, Lijun},
  year={2026}
}

License

This model is released under the Apache 2.0 license. The base model (Qwen3-4B-Base) is subject to its own license terms.

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