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---
name: pubchem-database
description: "Query PubChem via PUG-REST API/PubChemPy (110M+ compounds). Search by name/CID/SMILES, retrieve properties, similarity/substructure searches, bioactivity, for cheminformatics."
---
# PubChem Database
## Overview
PubChem is the world's largest freely available chemical database with 110M+ compounds and 270M+ bioactivities. Query chemical structures by name, CID, or SMILES, retrieve molecular properties, perform similarity and substructure searches, access bioactivity data using PUG-REST API and PubChemPy.
## When to Use This Skill
This skill should be used when:
- Searching for chemical compounds by name, structure (SMILES/InChI), or molecular formula
- Retrieving molecular properties (MW, LogP, TPSA, hydrogen bonding descriptors)
- Performing similarity searches to find structurally related compounds
- Conducting substructure searches for specific chemical motifs
- Accessing bioactivity data from screening assays
- Converting between chemical identifier formats (CID, SMILES, InChI)
- Batch processing multiple compounds for drug-likeness screening or property analysis
## Core Capabilities
### 1. Chemical Structure Search
Search for compounds using multiple identifier types:
**By Chemical Name**:
```python
import pubchempy as pcp
compounds = pcp.get_compounds('aspirin', 'name')
compound = compounds[0]
```
**By CID (Compound ID)**:
```python
compound = pcp.Compound.from_cid(2244) # Aspirin
```
**By SMILES**:
```python
compound = pcp.get_compounds('CC(=O)OC1=CC=CC=C1C(=O)O', 'smiles')[0]
```
**By InChI**:
```python
compound = pcp.get_compounds('InChI=1S/C9H8O4/...', 'inchi')[0]
```
**By Molecular Formula**:
```python
compounds = pcp.get_compounds('C9H8O4', 'formula')
# Returns all compounds matching this formula
```
### 2. Property Retrieval
Retrieve molecular properties for compounds using either high-level or low-level approaches:
**Using PubChemPy (Recommended)**:
```python
import pubchempy as pcp
# Get compound object with all properties
compound = pcp.get_compounds('caffeine', 'name')[0]
# Access individual properties
molecular_formula = compound.molecular_formula
molecular_weight = compound.molecular_weight
iupac_name = compound.iupac_name
smiles = compound.canonical_smiles
inchi = compound.inchi
xlogp = compound.xlogp # Partition coefficient
tpsa = compound.tpsa # Topological polar surface area
```
**Get Specific Properties**:
```python
# Request only specific properties
properties = pcp.get_properties(
['MolecularFormula', 'MolecularWeight', 'CanonicalSMILES', 'XLogP'],
'aspirin',
'name'
)
# Returns list of dictionaries
```
**Batch Property Retrieval**:
```python
import pandas as pd
compound_names = ['aspirin', 'ibuprofen', 'paracetamol']
all_properties = []
for name in compound_names:
props = pcp.get_properties(
['MolecularFormula', 'MolecularWeight', 'XLogP'],
name,
'name'
)
all_properties.extend(props)
df = pd.DataFrame(all_properties)
```
**Available Properties**: MolecularFormula, MolecularWeight, CanonicalSMILES, IsomericSMILES, InChI, InChIKey, IUPACName, XLogP, TPSA, HBondDonorCount, HBondAcceptorCount, RotatableBondCount, Complexity, Charge, and many more (see `references/api_reference.md` for complete list).
### 3. Similarity Search
Find structurally similar compounds using Tanimoto similarity:
```python
import pubchempy as pcp
# Start with a query compound
query_compound = pcp.get_compounds('gefitinib', 'name')[0]
query_smiles = query_compound.canonical_smiles
# Perform similarity search
similar_compounds = pcp.get_compounds(
query_smiles,
'smiles',
searchtype='similarity',
Threshold=85, # Similarity threshold (0-100)
MaxRecords=50
)
# Process results
for compound in similar_compounds[:10]:
print(f"CID {compound.cid}: {compound.iupac_name}")
print(f" MW: {compound.molecular_weight}")
```
**Note**: Similarity searches are asynchronous for large queries and may take 15-30 seconds to complete. PubChemPy handles the asynchronous pattern automatically.
### 4. Substructure Search
Find compounds containing a specific structural motif:
```python
import pubchempy as pcp
# Search for compounds containing pyridine ring
pyridine_smiles = 'c1ccncc1'
matches = pcp.get_compounds(
pyridine_smiles,
'smiles',
searchtype='substructure',
MaxRecords=100
)
print(f"Found {len(matches)} compounds containing pyridine")
```
**Common Substructures**:
- Benzene ring: `c1ccccc1`
- Pyridine: `c1ccncc1`
- Phenol: `c1ccc(O)cc1`
- Carboxylic acid: `C(=O)O`
### 5. Format Conversion
Convert between different chemical structure formats:
```python
import pubchempy as pcp
compound = pcp.get_compounds('aspirin', 'name')[0]
# Convert to different formats
smiles = compound.canonical_smiles
inchi = compound.inchi
inchikey = compound.inchikey
cid = compound.cid
# Download structure files
pcp.download('SDF', 'aspirin', 'name', 'aspirin.sdf', overwrite=True)
pcp.download('JSON', '2244', 'cid', 'aspirin.json', overwrite=True)
```
### 6. Structure Visualization
Generate 2D structure images:
```python
import pubchempy as pcp
# Download compound structure as PNG
pcp.download('PNG', 'caffeine', 'name', 'caffeine.png', overwrite=True)
# Using direct URL (via requests)
import requests
cid = 2244 # Aspirin
url = f"https://pubchem.ncbi.nlm.nih.gov/rest/pug/compound/cid/{cid}/PNG?image_size=large"
response = requests.get(url)
with open('structure.png', 'wb') as f:
f.write(response.content)
```
### 7. Synonym Retrieval
Get all known names and synonyms for a compound:
```python
import pubchempy as pcp
synonyms_data = pcp.get_synonyms('aspirin', 'name')
if synonyms_data:
cid = synonyms_data[0]['CID']
synonyms = synonyms_data[0]['Synonym']
print(f"CID {cid} has {len(synonyms)} synonyms:")
for syn in synonyms[:10]: # First 10
print(f" - {syn}")
```
### 8. Bioactivity Data Access
Retrieve biological activity data from assays:
```python
import requests
import json
# Get bioassay summary for a compound
cid = 2244 # Aspirin
url = f"https://pubchem.ncbi.nlm.nih.gov/rest/pug/compound/cid/{cid}/assaysummary/JSON"
response = requests.get(url)
if response.status_code == 200:
data = response.json()
# Process bioassay information
table = data.get('Table', {})
rows = table.get('Row', [])
print(f"Found {len(rows)} bioassay records")
```
**For more complex bioactivity queries**, use the `scripts/bioactivity_query.py` helper script which provides:
- Bioassay summaries with activity outcome filtering
- Assay target identification
- Search for compounds by biological target
- Active compound lists for specific assays
### 9. Comprehensive Compound Annotations
Access detailed compound information through PUG-View:
```python
import requests
cid = 2244
url = f"https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/{cid}/JSON"
response = requests.get(url)
if response.status_code == 200:
annotations = response.json()
# Contains extensive data including:
# - Chemical and Physical Properties
# - Drug and Medication Information
# - Pharmacology and Biochemistry
# - Safety and Hazards
# - Toxicity
# - Literature references
# - Patents
```
**Get Specific Section**:
```python
# Get only drug information
url = f"https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/{cid}/JSON?heading=Drug and Medication Information"
```
## Installation Requirements
Install PubChemPy for Python-based access:
```bash
uv pip install pubchempy
```
For direct API access and bioactivity queries:
```bash
uv pip install requests
```
Optional for data analysis:
```bash
uv pip install pandas
```
## Helper Scripts
This skill includes Python scripts for common PubChem tasks:
### scripts/compound_search.py
Provides utility functions for searching and retrieving compound information:
**Key Functions**:
- `search_by_name(name, max_results=10)`: Search compounds by name
- `search_by_smiles(smiles)`: Search by SMILES string
- `get_compound_by_cid(cid)`: Retrieve compound by CID
- `get_compound_properties(identifier, namespace, properties)`: Get specific properties
- `similarity_search(smiles, threshold, max_records)`: Perform similarity search
- `substructure_search(smiles, max_records)`: Perform substructure search
- `get_synonyms(identifier, namespace)`: Get all synonyms
- `batch_search(identifiers, namespace, properties)`: Batch search multiple compounds
- `download_structure(identifier, namespace, format, filename)`: Download structures
- `print_compound_info(compound)`: Print formatted compound information
**Usage**:
```python
from scripts.compound_search import search_by_name, get_compound_properties
# Search for a compound
compounds = search_by_name('ibuprofen')
# Get specific properties
props = get_compound_properties('aspirin', 'name', ['MolecularWeight', 'XLogP'])
```
### scripts/bioactivity_query.py
Provides functions for retrieving biological activity data:
**Key Functions**:
- `get_bioassay_summary(cid)`: Get bioassay summary for compound
- `get_compound_bioactivities(cid, activity_outcome)`: Get filtered bioactivities
- `get_assay_description(aid)`: Get detailed assay information
- `get_assay_targets(aid)`: Get biological targets for assay
- `search_assays_by_target(target_name, max_results)`: Find assays by target
- `get_active_compounds_in_assay(aid, max_results)`: Get active compounds
- `get_compound_annotations(cid, section)`: Get PUG-View annotations
- `summarize_bioactivities(cid)`: Generate bioactivity summary statistics
- `find_compounds_by_bioactivity(target, threshold, max_compounds)`: Find compounds by target
**Usage**:
```python
from scripts.bioactivity_query import get_bioassay_summary, summarize_bioactivities
# Get bioactivity summary
summary = summarize_bioactivities(2244) # Aspirin
print(f"Total assays: {summary['total_assays']}")
print(f"Active: {summary['active']}, Inactive: {summary['inactive']}")
```
## API Rate Limits and Best Practices
**Rate Limits**:
- Maximum 5 requests per second
- Maximum 400 requests per minute
- Maximum 300 seconds running time per minute
**Best Practices**:
1. **Use CIDs for repeated queries**: CIDs are more efficient than names or structures
2. **Cache results locally**: Store frequently accessed data
3. **Batch requests**: Combine multiple queries when possible
4. **Implement delays**: Add 0.2-0.3 second delays between requests
5. **Handle errors gracefully**: Check for HTTP errors and missing data
6. **Use PubChemPy**: Higher-level abstraction handles many edge cases
7. **Leverage asynchronous pattern**: For large similarity/substructure searches
8. **Specify MaxRecords**: Limit results to avoid timeouts
**Error Handling**:
```python
from pubchempy import BadRequestError, NotFoundError, TimeoutError
try:
compound = pcp.get_compounds('query', 'name')[0]
except NotFoundError:
print("Compound not found")
except BadRequestError:
print("Invalid request format")
except TimeoutError:
print("Request timed out - try reducing scope")
except IndexError:
print("No results returned")
```
## Common Workflows
### Workflow 1: Chemical Identifier Conversion Pipeline
Convert between different chemical identifiers:
```python
import pubchempy as pcp
# Start with any identifier type
compound = pcp.get_compounds('caffeine', 'name')[0]
# Extract all identifier formats
identifiers = {
'CID': compound.cid,
'Name': compound.iupac_name,
'SMILES': compound.canonical_smiles,
'InChI': compound.inchi,
'InChIKey': compound.inchikey,
'Formula': compound.molecular_formula
}
```
### Workflow 2: Drug-Like Property Screening
Screen compounds using Lipinski's Rule of Five:
```python
import pubchempy as pcp
def check_drug_likeness(compound_name):
compound = pcp.get_compounds(compound_name, 'name')[0]
# Lipinski's Rule of Five
rules = {
'MW <= 500': compound.molecular_weight <= 500,
'LogP <= 5': compound.xlogp <= 5 if compound.xlogp else None,
'HBD <= 5': compound.h_bond_donor_count <= 5,
'HBA <= 10': compound.h_bond_acceptor_count <= 10
}
violations = sum(1 for v in rules.values() if v is False)
return rules, violations
rules, violations = check_drug_likeness('aspirin')
print(f"Lipinski violations: {violations}")
```
### Workflow 3: Finding Similar Drug Candidates
Identify structurally similar compounds to a known drug:
```python
import pubchempy as pcp
# Start with known drug
reference_drug = pcp.get_compounds('imatinib', 'name')[0]
reference_smiles = reference_drug.canonical_smiles
# Find similar compounds
similar = pcp.get_compounds(
reference_smiles,
'smiles',
searchtype='similarity',
Threshold=85,
MaxRecords=20
)
# Filter by drug-like properties
candidates = []
for comp in similar:
if comp.molecular_weight and 200 <= comp.molecular_weight <= 600:
if comp.xlogp and -1 <= comp.xlogp <= 5:
candidates.append(comp)
print(f"Found {len(candidates)} drug-like candidates")
```
### Workflow 4: Batch Compound Property Comparison
Compare properties across multiple compounds:
```python
import pubchempy as pcp
import pandas as pd
compound_list = ['aspirin', 'ibuprofen', 'naproxen', 'celecoxib']
properties_list = []
for name in compound_list:
try:
compound = pcp.get_compounds(name, 'name')[0]
properties_list.append({
'Name': name,
'CID': compound.cid,
'Formula': compound.molecular_formula,
'MW': compound.molecular_weight,
'LogP': compound.xlogp,
'TPSA': compound.tpsa,
'HBD': compound.h_bond_donor_count,
'HBA': compound.h_bond_acceptor_count
})
except Exception as e:
print(f"Error processing {name}: {e}")
df = pd.DataFrame(properties_list)
print(df.to_string(index=False))
```
### Workflow 5: Substructure-Based Virtual Screening
Screen for compounds containing specific pharmacophores:
```python
import pubchempy as pcp
# Define pharmacophore (e.g., sulfonamide group)
pharmacophore_smiles = 'S(=O)(=O)N'
# Search for compounds containing this substructure
hits = pcp.get_compounds(
pharmacophore_smiles,
'smiles',
searchtype='substructure',
MaxRecords=100
)
# Further filter by properties
filtered_hits = [
comp for comp in hits
if comp.molecular_weight and comp.molecular_weight < 500
]
print(f"Found {len(filtered_hits)} compounds with desired substructure")
```
## Reference Documentation
For detailed API documentation, including complete property lists, URL patterns, advanced query options, and more examples, consult `references/api_reference.md`. This comprehensive reference includes:
- Complete PUG-REST API endpoint documentation
- Full list of available molecular properties
- Asynchronous request handling patterns
- PubChemPy API reference
- PUG-View API for annotations
- Common workflows and use cases
- Links to official PubChem documentation
## Troubleshooting
**Compound Not Found**:
- Try alternative names or synonyms
- Use CID if known
- Check spelling and chemical name format
**Timeout Errors**:
- Reduce MaxRecords parameter
- Add delays between requests
- Use CIDs instead of names for faster queries
**Empty Property Values**:
- Not all properties are available for all compounds
- Check if property exists before accessing: `if compound.xlogp:`
- Some properties only available for certain compound types
**Rate Limit Exceeded**:
- Implement delays (0.2-0.3 seconds) between requests
- Use batch operations where possible
- Consider caching results locally
**Similarity/Substructure Search Hangs**:
- These are asynchronous operations that may take 15-30 seconds
- PubChemPy handles polling automatically
- Reduce MaxRecords if timing out
## Additional Resources
- PubChem Home: https://pubchem.ncbi.nlm.nih.gov/
- PUG-REST Documentation: https://pubchem.ncbi.nlm.nih.gov/docs/pug-rest
- PUG-REST Tutorial: https://pubchem.ncbi.nlm.nih.gov/docs/pug-rest-tutorial
- PubChemPy Documentation: https://pubchempy.readthedocs.io/
- PubChemPy GitHub: https://github.com/mcs07/PubChemPy

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# PubChem API Reference
## Overview
PubChem is the world's largest freely available chemical database maintained by the National Center for Biotechnology Information (NCBI). It contains over 110 million unique chemical structures and over 270 million bioactivities from more than 770 data sources.
## Database Structure
PubChem consists of three primary subdatabases:
1. **Compound Database**: Unique validated chemical structures with computed properties
2. **Substance Database**: Deposited chemical substance records from data sources
3. **BioAssay Database**: Biological activity test results for chemical compounds
## PubChem PUG-REST API
### Base URL Structure
```
https://pubchem.ncbi.nlm.nih.gov/rest/pug/<input>/<operation>/<output>
```
Components:
- `<input>`: compound/cid, substance/sid, assay/aid, or search specifications
- `<operation>`: Optional operations like property, synonyms, classification, etc.
- `<output>`: Format such as JSON, XML, CSV, PNG, SDF, etc.
### Common Request Patterns
#### 1. Retrieve by Identifier
Get compound by CID (Compound ID):
```
GET /rest/pug/compound/cid/{cid}/property/{properties}/JSON
```
Get compound by name:
```
GET /rest/pug/compound/name/{name}/property/{properties}/JSON
```
Get compound by SMILES:
```
GET /rest/pug/compound/smiles/{smiles}/property/{properties}/JSON
```
Get compound by InChI:
```
GET /rest/pug/compound/inchi/{inchi}/property/{properties}/JSON
```
#### 2. Available Properties
Common molecular properties that can be retrieved:
- `MolecularFormula`
- `MolecularWeight`
- `CanonicalSMILES`
- `IsomericSMILES`
- `InChI`
- `InChIKey`
- `IUPACName`
- `XLogP`
- `ExactMass`
- `MonoisotopicMass`
- `TPSA` (Topological Polar Surface Area)
- `Complexity`
- `Charge`
- `HBondDonorCount`
- `HBondAcceptorCount`
- `RotatableBondCount`
- `HeavyAtomCount`
- `IsotopeAtomCount`
- `AtomStereoCount`
- `BondStereoCount`
- `CovalentUnitCount`
- `Volume3D`
- `XStericQuadrupole3D`
- `YStericQuadrupole3D`
- `ZStericQuadrupole3D`
- `FeatureCount3D`
To retrieve multiple properties, separate them with commas:
```
/property/MolecularFormula,MolecularWeight,CanonicalSMILES/JSON
```
#### 3. Structure Search Operations
**Similarity Search**:
```
POST /rest/pug/compound/similarity/smiles/{smiles}/JSON
Parameters: Threshold (default 90%)
```
**Substructure Search**:
```
POST /rest/pug/compound/substructure/smiles/{smiles}/cids/JSON
```
**Superstructure Search**:
```
POST /rest/pug/compound/superstructure/smiles/{smiles}/cids/JSON
```
#### 4. Image Generation
Get 2D structure image:
```
GET /rest/pug/compound/cid/{cid}/PNG
Optional parameters: image_size=small|large
```
#### 5. Format Conversion
Get compound as SDF (Structure-Data File):
```
GET /rest/pug/compound/cid/{cid}/SDF
```
Get compound as MOL:
```
GET /rest/pug/compound/cid/{cid}/record/SDF
```
#### 6. Synonym Retrieval
Get all synonyms for a compound:
```
GET /rest/pug/compound/cid/{cid}/synonyms/JSON
```
#### 7. Bioassay Data
Get bioassay data for a compound:
```
GET /rest/pug/compound/cid/{cid}/assaysummary/JSON
```
Get specific assay information:
```
GET /rest/pug/assay/aid/{aid}/description/JSON
```
### Asynchronous Requests
For large queries (similarity/substructure searches), PUG-REST uses an asynchronous pattern:
1. Submit the query (returns ListKey)
2. Check status using the ListKey
3. Retrieve results when ready
Example workflow:
```python
# Step 1: Submit similarity search
response = requests.post(
"https://pubchem.ncbi.nlm.nih.gov/rest/pug/compound/similarity/smiles/{smiles}/cids/JSON",
data={"Threshold": 90}
)
listkey = response.json()["Waiting"]["ListKey"]
# Step 2: Check status
status_url = f"https://pubchem.ncbi.nlm.nih.gov/rest/pug/compound/listkey/{listkey}/cids/JSON"
# Step 3: Poll until ready (with timeout)
# Step 4: Retrieve results from the same URL
```
### Usage Limits
**Rate Limits**:
- Maximum 5 requests per second
- Maximum 400 requests per minute
- Maximum 300 seconds running time per minute
**Best Practices**:
- Use batch requests when possible
- Implement exponential backoff for retries
- Cache results when appropriate
- Use asynchronous pattern for large queries
## PubChemPy Python Library
PubChemPy is a Python wrapper that simplifies PUG-REST API access.
### Installation
```bash
pip install pubchempy
```
### Key Classes
#### Compound Class
Main class for representing chemical compounds:
```python
import pubchempy as pcp
# Get by CID
compound = pcp.Compound.from_cid(2244)
# Access properties
compound.molecular_formula # 'C9H8O4'
compound.molecular_weight # 180.16
compound.iupac_name # '2-acetyloxybenzoic acid'
compound.canonical_smiles # 'CC(=O)OC1=CC=CC=C1C(=O)O'
compound.isomeric_smiles # Same as canonical for non-stereoisomers
compound.inchi # InChI string
compound.inchikey # InChI Key
compound.xlogp # Partition coefficient
compound.tpsa # Topological polar surface area
```
#### Search Methods
**By Name**:
```python
compounds = pcp.get_compounds('aspirin', 'name')
# Returns list of Compound objects
```
**By SMILES**:
```python
compound = pcp.get_compounds('CC(=O)OC1=CC=CC=C1C(=O)O', 'smiles')[0]
```
**By InChI**:
```python
compound = pcp.get_compounds('InChI=1S/C9H8O4/c1-6(10)13-8-5-3-2-4-7(8)9(11)12/h2-5H,1H3,(H,11,12)', 'inchi')[0]
```
**By Formula**:
```python
compounds = pcp.get_compounds('C9H8O4', 'formula')
# Returns all compounds with this formula
```
**Similarity Search**:
```python
results = pcp.get_compounds('CC(=O)OC1=CC=CC=C1C(=O)O', 'smiles',
searchtype='similarity',
Threshold=90)
```
**Substructure Search**:
```python
results = pcp.get_compounds('c1ccccc1', 'smiles',
searchtype='substructure')
# Returns all compounds containing benzene ring
```
#### Property Retrieval
Get specific properties for multiple compounds:
```python
properties = pcp.get_properties(
['MolecularFormula', 'MolecularWeight', 'CanonicalSMILES'],
'aspirin',
'name'
)
# Returns list of dictionaries
```
Get properties as pandas DataFrame:
```python
import pandas as pd
df = pd.DataFrame(properties)
```
#### Synonyms
Get all synonyms for a compound:
```python
synonyms = pcp.get_synonyms('aspirin', 'name')
# Returns list of dictionaries with CID and synonym lists
```
#### Download Formats
Download compound in various formats:
```python
# Get as SDF
sdf_data = pcp.download('SDF', 'aspirin', 'name', overwrite=True)
# Get as JSON
json_data = pcp.download('JSON', '2244', 'cid')
# Get as PNG image
pcp.download('PNG', '2244', 'cid', 'aspirin.png', overwrite=True)
```
### Error Handling
```python
from pubchempy import BadRequestError, NotFoundError, TimeoutError
try:
compound = pcp.get_compounds('nonexistent', 'name')
except NotFoundError:
print("Compound not found")
except BadRequestError:
print("Invalid request")
except TimeoutError:
print("Request timed out")
```
## PUG-View API
PUG-View provides access to full textual annotations and specialized reports.
### Key Endpoints
Get compound annotations:
```
GET /rest/pug_view/data/compound/{cid}/JSON
```
Get specific annotation sections:
```
GET /rest/pug_view/data/compound/{cid}/JSON?heading={section_name}
```
Available sections include:
- Chemical and Physical Properties
- Drug and Medication Information
- Pharmacology and Biochemistry
- Safety and Hazards
- Toxicity
- Literature
- Patents
- Biomolecular Interactions and Pathways
## Common Workflows
### 1. Chemical Identifier Conversion
Convert from name to SMILES to InChI:
```python
import pubchempy as pcp
compound = pcp.get_compounds('caffeine', 'name')[0]
smiles = compound.canonical_smiles
inchi = compound.inchi
inchikey = compound.inchikey
cid = compound.cid
```
### 2. Batch Property Retrieval
Get properties for multiple compounds:
```python
compound_names = ['aspirin', 'ibuprofen', 'paracetamol']
properties = []
for name in compound_names:
props = pcp.get_properties(
['MolecularFormula', 'MolecularWeight', 'XLogP'],
name,
'name'
)
properties.extend(props)
import pandas as pd
df = pd.DataFrame(properties)
```
### 3. Finding Similar Compounds
Find structurally similar compounds to a query:
```python
# Start with a known compound
query_compound = pcp.get_compounds('gefitinib', 'name')[0]
query_smiles = query_compound.canonical_smiles
# Perform similarity search
similar = pcp.get_compounds(
query_smiles,
'smiles',
searchtype='similarity',
Threshold=85
)
# Get properties for similar compounds
for compound in similar[:10]: # First 10 results
print(f"{compound.cid}: {compound.iupac_name}, MW: {compound.molecular_weight}")
```
### 4. Substructure Screening
Find all compounds containing a specific substructure:
```python
# Search for compounds containing pyridine ring
pyridine_smiles = 'c1ccncc1'
matches = pcp.get_compounds(
pyridine_smiles,
'smiles',
searchtype='substructure',
MaxRecords=100
)
print(f"Found {len(matches)} compounds containing pyridine")
```
### 5. Bioactivity Data Retrieval
```python
import requests
cid = 2244 # Aspirin
url = f"https://pubchem.ncbi.nlm.nih.gov/rest/pug/compound/cid/{cid}/assaysummary/JSON"
response = requests.get(url)
if response.status_code == 200:
bioassay_data = response.json()
# Process bioassay information
```
## Tips and Best Practices
1. **Use CIDs for repeated queries**: CIDs are more efficient than names or structures
2. **Cache results**: Store frequently accessed data locally
3. **Batch requests**: Combine multiple queries when possible
4. **Handle rate limits**: Implement delays between requests
5. **Use appropriate search types**: Similarity for related compounds, substructure for motif finding
6. **Leverage PubChemPy**: Higher-level abstraction simplifies common tasks
7. **Handle missing data**: Not all properties are available for all compounds
8. **Use asynchronous pattern**: For large similarity/substructure searches
9. **Specify output format**: Choose JSON for programmatic access, SDF for cheminformatics tools
10. **Read documentation**: Full PUG-REST documentation available at https://pubchem.ncbi.nlm.nih.gov/docs/pug-rest
## Additional Resources
- PubChem Home: https://pubchem.ncbi.nlm.nih.gov/
- PUG-REST Documentation: https://pubchem.ncbi.nlm.nih.gov/docs/pug-rest
- PUG-REST Tutorial: https://pubchem.ncbi.nlm.nih.gov/docs/pug-rest-tutorial
- PubChemPy Documentation: https://pubchempy.readthedocs.io/
- PubChemPy GitHub: https://github.com/mcs07/PubChemPy
- IUPAC Tutorial: https://iupac.github.io/WFChemCookbook/datasources/pubchem_pugrest.html

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#!/usr/bin/env python3
"""
PubChem Bioactivity Data Retrieval
This script provides functions for retrieving biological activity data
from PubChem for compounds and assays.
"""
import sys
import json
import time
from typing import Dict, List, Optional
try:
import requests
except ImportError:
print("Error: requests is not installed. Install it with: pip install requests")
sys.exit(1)
BASE_URL = "https://pubchem.ncbi.nlm.nih.gov/rest/pug"
PUG_VIEW_URL = "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view"
# Rate limiting: 5 requests per second maximum
REQUEST_DELAY = 0.21 # seconds between requests
def rate_limited_request(url: str, method: str = 'GET', **kwargs) -> Optional[requests.Response]:
"""
Make a rate-limited request to PubChem API.
Args:
url: Request URL
method: HTTP method ('GET' or 'POST')
**kwargs: Additional arguments for requests
Returns:
Response object or None on error
"""
time.sleep(REQUEST_DELAY)
try:
if method.upper() == 'GET':
response = requests.get(url, **kwargs)
else:
response = requests.post(url, **kwargs)
response.raise_for_status()
return response
except requests.exceptions.RequestException as e:
print(f"Request error: {e}")
return None
def get_bioassay_summary(cid: int) -> Optional[Dict]:
"""
Get bioassay summary for a compound.
Args:
cid: PubChem Compound ID
Returns:
Dictionary containing bioassay summary data
"""
url = f"{BASE_URL}/compound/cid/{cid}/assaysummary/JSON"
response = rate_limited_request(url)
if response and response.status_code == 200:
return response.json()
return None
def get_compound_bioactivities(
cid: int,
activity_outcome: Optional[str] = None
) -> List[Dict]:
"""
Get bioactivity data for a compound.
Args:
cid: PubChem Compound ID
activity_outcome: Filter by activity ('active', 'inactive', 'inconclusive')
Returns:
List of bioactivity records
"""
data = get_bioassay_summary(cid)
if not data:
return []
activities = []
table = data.get('Table', {})
for row in table.get('Row', []):
activity = {}
for i, cell in enumerate(row.get('Cell', [])):
column_name = table['Columns']['Column'][i]
activity[column_name] = cell
if activity_outcome:
if activity.get('Activity Outcome', '').lower() == activity_outcome.lower():
activities.append(activity)
else:
activities.append(activity)
return activities
def get_assay_description(aid: int) -> Optional[Dict]:
"""
Get detailed description for a specific assay.
Args:
aid: PubChem Assay ID (AID)
Returns:
Dictionary containing assay description
"""
url = f"{BASE_URL}/assay/aid/{aid}/description/JSON"
response = rate_limited_request(url)
if response and response.status_code == 200:
return response.json()
return None
def get_assay_targets(aid: int) -> List[str]:
"""
Get biological targets for an assay.
Args:
aid: PubChem Assay ID
Returns:
List of target names
"""
description = get_assay_description(aid)
if not description:
return []
targets = []
assay_data = description.get('PC_AssayContainer', [{}])[0]
assay = assay_data.get('assay', {})
# Extract target information
descr = assay.get('descr', {})
for target in descr.get('target', []):
mol_id = target.get('mol_id', '')
name = target.get('name', '')
if name:
targets.append(name)
elif mol_id:
targets.append(f"GI:{mol_id}")
return targets
def search_assays_by_target(
target_name: str,
max_results: int = 100
) -> List[int]:
"""
Search for assays targeting a specific protein or gene.
Args:
target_name: Name of the target (e.g., 'EGFR', 'p53')
max_results: Maximum number of results
Returns:
List of Assay IDs (AIDs)
"""
# Use PubChem's text search for assays
url = f"{BASE_URL}/assay/target/{target_name}/aids/JSON"
response = rate_limited_request(url)
if response and response.status_code == 200:
data = response.json()
aids = data.get('IdentifierList', {}).get('AID', [])
return aids[:max_results]
return []
def get_active_compounds_in_assay(aid: int, max_results: int = 1000) -> List[int]:
"""
Get list of active compounds in an assay.
Args:
aid: PubChem Assay ID
max_results: Maximum number of results
Returns:
List of Compound IDs (CIDs) that showed activity
"""
url = f"{BASE_URL}/assay/aid/{aid}/cids/JSON?cids_type=active"
response = rate_limited_request(url)
if response and response.status_code == 200:
data = response.json()
cids = data.get('IdentifierList', {}).get('CID', [])
return cids[:max_results]
return []
def get_compound_annotations(cid: int, section: Optional[str] = None) -> Optional[Dict]:
"""
Get comprehensive compound annotations from PUG-View.
Args:
cid: PubChem Compound ID
section: Specific section to retrieve (e.g., 'Pharmacology and Biochemistry')
Returns:
Dictionary containing annotation data
"""
url = f"{PUG_VIEW_URL}/data/compound/{cid}/JSON"
if section:
url += f"?heading={section}"
response = rate_limited_request(url)
if response and response.status_code == 200:
return response.json()
return None
def get_drug_information(cid: int) -> Optional[Dict]:
"""
Get drug and medication information for a compound.
Args:
cid: PubChem Compound ID
Returns:
Dictionary containing drug information
"""
return get_compound_annotations(cid, section="Drug and Medication Information")
def get_safety_hazards(cid: int) -> Optional[Dict]:
"""
Get safety and hazard information for a compound.
Args:
cid: PubChem Compound ID
Returns:
Dictionary containing safety information
"""
return get_compound_annotations(cid, section="Safety and Hazards")
def summarize_bioactivities(cid: int) -> Dict:
"""
Generate a summary of bioactivity data for a compound.
Args:
cid: PubChem Compound ID
Returns:
Dictionary with bioactivity summary statistics
"""
activities = get_compound_bioactivities(cid)
summary = {
'total_assays': len(activities),
'active': 0,
'inactive': 0,
'inconclusive': 0,
'unspecified': 0,
'assay_types': {}
}
for activity in activities:
outcome = activity.get('Activity Outcome', '').lower()
if 'active' in outcome:
summary['active'] += 1
elif 'inactive' in outcome:
summary['inactive'] += 1
elif 'inconclusive' in outcome:
summary['inconclusive'] += 1
else:
summary['unspecified'] += 1
return summary
def find_compounds_by_bioactivity(
target: str,
threshold: Optional[float] = None,
max_compounds: int = 100
) -> List[Dict]:
"""
Find compounds with bioactivity against a specific target.
Args:
target: Target name (e.g., 'EGFR')
threshold: Activity threshold (if applicable)
max_compounds: Maximum number of compounds to return
Returns:
List of dictionaries with compound information and activity data
"""
# Step 1: Find assays for the target
assay_ids = search_assays_by_target(target, max_results=10)
if not assay_ids:
print(f"No assays found for target: {target}")
return []
# Step 2: Get active compounds from these assays
compound_set = set()
compound_data = []
for aid in assay_ids[:5]: # Limit to first 5 assays
active_cids = get_active_compounds_in_assay(aid, max_results=max_compounds)
for cid in active_cids:
if cid not in compound_set and len(compound_data) < max_compounds:
compound_set.add(cid)
compound_data.append({
'cid': cid,
'aid': aid,
'target': target
})
if len(compound_data) >= max_compounds:
break
return compound_data
def main():
"""Example usage of bioactivity query functions."""
# Example 1: Get bioassay summary for aspirin (CID 2244)
print("Example 1: Getting bioassay summary for aspirin (CID 2244)...")
summary = summarize_bioactivities(2244)
print(json.dumps(summary, indent=2))
# Example 2: Get active bioactivities for a compound
print("\nExample 2: Getting active bioactivities for aspirin...")
activities = get_compound_bioactivities(2244, activity_outcome='active')
print(f"Found {len(activities)} active bioactivities")
if activities:
print(f"First activity: {activities[0].get('Assay Name', 'N/A')}")
# Example 3: Get assay information
print("\nExample 3: Getting assay description...")
if activities:
aid = activities[0].get('AID', 0)
targets = get_assay_targets(aid)
print(f"Assay {aid} targets: {', '.join(targets) if targets else 'N/A'}")
# Example 4: Search for compounds targeting EGFR
print("\nExample 4: Searching for EGFR inhibitors...")
egfr_compounds = find_compounds_by_bioactivity('EGFR', max_compounds=5)
print(f"Found {len(egfr_compounds)} compounds with EGFR activity")
for comp in egfr_compounds[:5]:
print(f" CID {comp['cid']} (from AID {comp['aid']})")
if __name__ == '__main__':
main()

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#!/usr/bin/env python3
"""
PubChem Compound Search Utility
This script provides functions for searching and retrieving compound information
from PubChem using the PubChemPy library.
"""
import sys
import json
from typing import List, Dict, Optional, Union
try:
import pubchempy as pcp
except ImportError:
print("Error: pubchempy is not installed. Install it with: pip install pubchempy")
sys.exit(1)
def search_by_name(name: str, max_results: int = 10) -> List[pcp.Compound]:
"""
Search for compounds by name.
Args:
name: Chemical name to search for
max_results: Maximum number of results to return
Returns:
List of Compound objects
"""
try:
compounds = pcp.get_compounds(name, 'name')
return compounds[:max_results]
except Exception as e:
print(f"Error searching for '{name}': {e}")
return []
def search_by_smiles(smiles: str) -> Optional[pcp.Compound]:
"""
Search for a compound by SMILES string.
Args:
smiles: SMILES string
Returns:
Compound object or None if not found
"""
try:
compounds = pcp.get_compounds(smiles, 'smiles')
return compounds[0] if compounds else None
except Exception as e:
print(f"Error searching for SMILES '{smiles}': {e}")
return None
def get_compound_by_cid(cid: int) -> Optional[pcp.Compound]:
"""
Retrieve a compound by its CID (Compound ID).
Args:
cid: PubChem Compound ID
Returns:
Compound object or None if not found
"""
try:
return pcp.Compound.from_cid(cid)
except Exception as e:
print(f"Error retrieving CID {cid}: {e}")
return None
def get_compound_properties(
identifier: Union[str, int],
namespace: str = 'name',
properties: Optional[List[str]] = None
) -> Dict:
"""
Get specific properties for a compound.
Args:
identifier: Compound identifier (name, SMILES, CID, etc.)
namespace: Type of identifier ('name', 'smiles', 'cid', 'inchi', etc.)
properties: List of properties to retrieve. If None, returns common properties.
Returns:
Dictionary of properties
"""
if properties is None:
properties = [
'MolecularFormula',
'MolecularWeight',
'CanonicalSMILES',
'IUPACName',
'XLogP',
'TPSA',
'HBondDonorCount',
'HBondAcceptorCount'
]
try:
result = pcp.get_properties(properties, identifier, namespace)
return result[0] if result else {}
except Exception as e:
print(f"Error getting properties for '{identifier}': {e}")
return {}
def similarity_search(
smiles: str,
threshold: int = 90,
max_records: int = 10
) -> List[pcp.Compound]:
"""
Perform similarity search for compounds similar to the query structure.
Args:
smiles: Query SMILES string
threshold: Similarity threshold (0-100)
max_records: Maximum number of results
Returns:
List of similar Compound objects
"""
try:
compounds = pcp.get_compounds(
smiles,
'smiles',
searchtype='similarity',
Threshold=threshold,
MaxRecords=max_records
)
return compounds
except Exception as e:
print(f"Error in similarity search: {e}")
return []
def substructure_search(
smiles: str,
max_records: int = 100
) -> List[pcp.Compound]:
"""
Perform substructure search for compounds containing the query structure.
Args:
smiles: Query SMILES string (substructure)
max_records: Maximum number of results
Returns:
List of Compound objects containing the substructure
"""
try:
compounds = pcp.get_compounds(
smiles,
'smiles',
searchtype='substructure',
MaxRecords=max_records
)
return compounds
except Exception as e:
print(f"Error in substructure search: {e}")
return []
def get_synonyms(identifier: Union[str, int], namespace: str = 'name') -> List[str]:
"""
Get all synonyms for a compound.
Args:
identifier: Compound identifier
namespace: Type of identifier
Returns:
List of synonym strings
"""
try:
results = pcp.get_synonyms(identifier, namespace)
if results:
return results[0].get('Synonym', [])
return []
except Exception as e:
print(f"Error getting synonyms: {e}")
return []
def batch_search(
identifiers: List[str],
namespace: str = 'name',
properties: Optional[List[str]] = None
) -> List[Dict]:
"""
Batch search for multiple compounds.
Args:
identifiers: List of compound identifiers
namespace: Type of identifiers
properties: List of properties to retrieve
Returns:
List of dictionaries containing properties for each compound
"""
results = []
for identifier in identifiers:
props = get_compound_properties(identifier, namespace, properties)
if props:
props['query'] = identifier
results.append(props)
return results
def download_structure(
identifier: Union[str, int],
namespace: str = 'name',
format: str = 'SDF',
filename: Optional[str] = None
) -> Optional[str]:
"""
Download compound structure in specified format.
Args:
identifier: Compound identifier
namespace: Type of identifier
format: Output format ('SDF', 'JSON', 'PNG', etc.)
filename: Output filename (if None, returns data as string)
Returns:
Data string if filename is None, else None
"""
try:
if filename:
pcp.download(format, identifier, namespace, filename, overwrite=True)
return None
else:
return pcp.download(format, identifier, namespace)
except Exception as e:
print(f"Error downloading structure: {e}")
return None
def print_compound_info(compound: pcp.Compound) -> None:
"""
Print formatted compound information.
Args:
compound: PubChemPy Compound object
"""
print(f"\n{'='*60}")
print(f"Compound CID: {compound.cid}")
print(f"{'='*60}")
print(f"IUPAC Name: {compound.iupac_name or 'N/A'}")
print(f"Molecular Formula: {compound.molecular_formula or 'N/A'}")
print(f"Molecular Weight: {compound.molecular_weight or 'N/A'} g/mol")
print(f"Canonical SMILES: {compound.canonical_smiles or 'N/A'}")
print(f"InChI: {compound.inchi or 'N/A'}")
print(f"InChI Key: {compound.inchikey or 'N/A'}")
print(f"XLogP: {compound.xlogp or 'N/A'}")
print(f"TPSA: {compound.tpsa or 'N/A'} Ų")
print(f"H-Bond Donors: {compound.h_bond_donor_count or 'N/A'}")
print(f"H-Bond Acceptors: {compound.h_bond_acceptor_count or 'N/A'}")
print(f"{'='*60}\n")
def main():
"""Example usage of PubChem search functions."""
# Example 1: Search by name
print("Example 1: Searching for 'aspirin'...")
compounds = search_by_name('aspirin', max_results=1)
if compounds:
print_compound_info(compounds[0])
# Example 2: Get properties
print("\nExample 2: Getting properties for caffeine...")
props = get_compound_properties('caffeine', 'name')
print(json.dumps(props, indent=2))
# Example 3: Similarity search
print("\nExample 3: Finding compounds similar to benzene...")
benzene_smiles = 'c1ccccc1'
similar = similarity_search(benzene_smiles, threshold=95, max_records=5)
print(f"Found {len(similar)} similar compounds:")
for comp in similar:
print(f" CID {comp.cid}: {comp.iupac_name or 'N/A'}")
# Example 4: Batch search
print("\nExample 4: Batch search for multiple compounds...")
names = ['aspirin', 'ibuprofen', 'paracetamol']
results = batch_search(names, properties=['MolecularFormula', 'MolecularWeight'])
for result in results:
print(f" {result.get('query')}: {result.get('MolecularFormula')} "
f"({result.get('MolecularWeight')} g/mol)")
if __name__ == '__main__':
main()