Cheminformatics

# Cheminformatics

Part of [Agent Skills™](https://github.com/itallstartedwithaidea/agent-skills) by [googleadsagent.ai™](https://googleadsagent.ai)

## Description

Cheminformatics provides computational chemistry workflows using RDKit for molecular property prediction, virtual screening, ADMET analysis, molecular docking preparation, and chemical space exploration. The agent generates reproducible cheminformatics pipelines that transform molecular structures (SMILES, SDF) into actionable predictions about drug-likeness, toxicity, and binding affinity.

Drug discovery generates vast chemical libraries that cannot all be synthesized and tested. Cheminformatics narrows the search space computationally: filtering by Lipinski's Rule of Five, predicting ADMET properties (Absorption, Distribution, Metabolism, Excretion, Toxicity), scoring docking poses, and clustering chemical space to identify diverse lead candidates. Each step eliminates compounds that would fail in later, more expensive stages.

This skill covers the molecular informatics workflow from SMILES parsing through descriptor calculation, fingerprint generation, similarity searching, property prediction, and visualization. It integrates with databases like PubChem and ChEMBL for compound retrieval and benchmarking against known actives and inactives.

## Use When

- Calculating molecular properties and descriptors
- Screening compound libraries for drug-likeness
- Predicting ADMET properties for lead compounds
- Performing molecular similarity searches
- Preparing structures for molecular docking
- Visualizing chemical space and structure-activity relationships

## How It Works

```mermaid
graph TD
    A[Molecular Input: SMILES/SDF] --> B[Parse + Validate Structures]
    B --> C[Calculate Descriptors]
    C --> D[Drug-likeness Filters]
    D --> E{Passes Lipinski?}
    E -->|No| F[Flag as Non-Drug-like]
    E -->|Yes| G[ADMET Prediction]
    G --> H[Virtual Screening Score]
    H --> I[Docking Preparation]
    I --> J[Ranked Candidate List]
    F --> K[Report with Flags]
    J --> K
```

Compounds flow through increasingly selective filters. Drug-likeness removes obviously non-viable candidates, ADMET prediction flags absorption and toxicity risks, and virtual screening ranks the survivors by predicted activity.

## Implementation

```python
from rdkit import Chem
from rdkit.Chem import Descriptors, AllChem, Draw, Lipinski, DataStructs
from rdkit.Chem import rdMolDescriptors
import pandas as pd

def molecular_properties(smiles: str) -> dict:
    mol = Chem.MolFromSmiles(smiles)
    if mol is None:
        raise ValueError(f"Invalid SMILES: {smiles}")
    return {
        "smiles": smiles,
        "mw": Descriptors.MolWt(mol),
        "logp": Descriptors.MolLogP(mol),
        "hbd": Descriptors.NumHDonors(mol),
        "hba": Descriptors.NumHAcceptors(mol),
        "tpsa": Descriptors.TPSA(mol),
        "rotatable_bonds": Descriptors.NumRotatableBonds(mol),
        "rings": Descriptors.RingCount(mol),
        "lipinski_violations": sum([
            Descriptors.MolWt(mol) > 500,
            Descriptors.MolLogP(mol) > 5,
            Descriptors.NumHDonors(mol) > 5,
            Descriptors.NumHAcceptors(mol) > 10,
        ]),
    }

def lipinski_filter(df: pd.DataFrame) -> pd.DataFrame:
    return df[df["lipinski_violations"] <= 1].copy()

def similarity_search(query_smiles: str, library: list[str], threshold: float = 0.7) -> list[dict]:
    query_mol = Chem.MolFromSmiles(query_smiles)
    query_fp = AllChem.GetMorganFingerprintAsBitVect(query_mol, radius=2, nBits=2048)

    results = []
    for smi in library:
        mol = Chem.MolFromSmiles(smi)
        if mol is None:
            continue
        fp = AllChem.GetMorganF