Initial commit

2025-11-30 08:30:10 +08:00
commit f0bd18fb4e
824 changed files with 331919 additions and 0 deletions
--- a/skills/string-database/references/string_reference.md
+++ b/skills/string-database/references/string_reference.md
@@ -0,0 +1,455 @@
+# STRING Database API Reference
+
+## Overview
+
+STRING (Search Tool for the Retrieval of Interacting Genes/Proteins) is a comprehensive database of known and predicted protein-protein interactions integrating data from over 40 sources.
+
+**Database Statistics (v12.0+):**
+- Coverage: 5000+ genomes
+- Proteins: ~59.3 million
+- Interactions: 20+ billion
+- Data types: Physical interactions, functional associations, co-expression, co-occurrence, text-mining, databases
+
+**Core Data Resource:** Designated by Global Biodata Coalition and ELIXIR
+
+## API Base URLs
+
+- **Current version**: https://string-db.org/api
+- **Version-specific**: https://version-12-0.string-db.org/api (for reproducibility)
+- **API documentation**: https://string-db.org/help/api/
+
+## Best Practices
+
+1. **Identifier Mapping**: Always map identifiers first using `get_string_ids` for faster subsequent queries
+2. **Use STRING IDs**: Prefer STRING identifiers (e.g., `9606.ENSP00000269305`) over gene names
+3. **Specify Species**: For networks with >10 proteins, always specify species NCBI taxon ID
+4. **Rate Limiting**: Wait 1 second between API calls to avoid server overload
+5. **Versioned URLs**: Use version-specific URLs for reproducible research
+6. **POST over GET**: Use POST requests for large protein lists
+7. **Caller Identity**: Include `caller_identity` parameter for tracking (e.g., your application name)
+
+## API Methods
+
+### 1. Identifier Mapping (`get_string_ids`)
+
+**Purpose**: Maps common protein names, gene symbols, UniProt IDs, and other identifiers to STRING identifiers.
+
+**Endpoint**: `/api/tsv/get_string_ids`
+
+**Parameters**:
+- `identifiers` (required): Protein names/IDs separated by newlines (`%0d`)
+- `species` (required): NCBI taxon ID
+- `limit`: Number of matches per identifier (default: 1)
+- `echo_query`: Include query term in output (1 or 0)
+- `caller_identity`: Application identifier
+
+**Output Format**: TSV with columns:
+- `queryItem`: Original query
+- `queryIndex`: Query position
+- `stringId`: STRING identifier
+- `ncbiTaxonId`: Species taxon ID
+- `taxonName`: Species name
+- `preferredName`: Preferred gene name
+- `annotation`: Protein description
+
+**Example**:
+```
+identifiers=TP53%0dBRCA1&species=9606&limit=1
+```
+
+**Use cases**:
+- Converting gene symbols to STRING IDs
+- Validating protein identifiers
+- Finding canonical protein names
+
+### 2. Network Data (`network`)
+
+**Purpose**: Retrieves protein-protein interaction network data in tabular format.
+
+**Endpoint**: `/api/tsv/network`
+
+**Parameters**:
+- `identifiers` (required): Protein IDs separated by `%0d`
+- `species`: NCBI taxon ID
+- `required_score`: Confidence threshold 0-1000 (default: 400)
+  - 150: low confidence
+  - 400: medium confidence
+  - 700: high confidence
+  - 900: highest confidence
+- `network_type`: `functional` (default) or `physical`
+- `add_nodes`: Add N interacting proteins (0-10)
+- `caller_identity`: Application identifier
+
+**Output Format**: TSV with columns:
+- `stringId_A`, `stringId_B`: Interacting proteins
+- `preferredName_A`, `preferredName_B`: Gene names
+- `ncbiTaxonId`: Species
+- `score`: Combined interaction score (0-1000)
+- `nscore`: Neighborhood score
+- `fscore`: Fusion score
+- `pscore`: Phylogenetic profile score
+- `ascore`: Coexpression score
+- `escore`: Experimental score
+- `dscore`: Database score
+- `tscore`: Text-mining score
+
+**Network Types**:
+- **Functional**: All interaction evidence types (recommended for most analyses)
+- **Physical**: Only direct physical binding evidence
+
+**Example**:
+```
+identifiers=9606.ENSP00000269305%0d9606.ENSP00000275493&required_score=700
+```
+
+### 3. Network Image (`image/network`)
+
+**Purpose**: Generates visual network representation as PNG image.
+
+**Endpoint**: `/api/image/network`
+
+**Parameters**:
+- `identifiers` (required): Protein IDs separated by `%0d`
+- `species`: NCBI taxon ID
+- `required_score`: Confidence threshold 0-1000
+- `network_flavor`: Visualization style
+  - `evidence`: Show evidence types as colored lines
+  - `confidence`: Show confidence as line thickness
+  - `actions`: Show activating/inhibiting interactions
+- `add_nodes`: Add N interacting proteins (0-10)
+- `caller_identity`: Application identifier
+
+**Output**: PNG image (binary data)
+
+**Image Specifications**:
+- Format: PNG
+- Size: Automatically scaled based on network size
+- High-resolution option available (add `?highres=1`)
+
+**Example**:
+```
+identifiers=TP53%0dMDM2&species=9606&network_flavor=evidence
+```
+
+### 4. Interaction Partners (`interaction_partners`)
+
+**Purpose**: Retrieves all STRING interaction partners for given protein(s).
+
+**Endpoint**: `/api/tsv/interaction_partners`
+
+**Parameters**:
+- `identifiers` (required): Protein IDs
+- `species`: NCBI taxon ID
+- `required_score`: Confidence threshold 0-1000
+- `limit`: Maximum number of partners (default: 10)
+- `caller_identity`: Application identifier
+
+**Output Format**: TSV with same columns as `network` method
+
+**Use cases**:
+- Finding hub proteins
+- Expanding networks
+- Discovery of novel interactions
+
+**Example**:
+```
+identifiers=TP53&species=9606&limit=20&required_score=700
+```
+
+### 5. Functional Enrichment (`enrichment`)
+
+**Purpose**: Performs functional enrichment analysis for a set of proteins across multiple annotation databases.
+
+**Endpoint**: `/api/tsv/enrichment`
+
+**Parameters**:
+- `identifiers` (required): List of protein IDs
+- `species` (required): NCBI taxon ID
+- `caller_identity`: Application identifier
+
+**Enrichment Categories**:
+- **Gene Ontology**: Biological Process, Molecular Function, Cellular Component
+- **KEGG Pathways**: Metabolic and signaling pathways
+- **Pfam**: Protein domains
+- **InterPro**: Protein families and domains
+- **SMART**: Domain architecture
+- **UniProt Keywords**: Curated functional keywords
+
+**Output Format**: TSV with columns:
+- `category`: Annotation category
+- `term`: Term ID
+- `description`: Term description
+- `number_of_genes`: Genes in input with this term
+- `number_of_genes_in_background`: Total genes with this term
+- `ncbiTaxonId`: Species
+- `inputGenes`: Comma-separated gene list
+- `preferredNames`: Comma-separated gene names
+- `p_value`: Enrichment p-value (uncorrected)
+- `fdr`: False discovery rate (corrected p-value)
+
+**Statistical Method**: Fisher's exact test with Benjamini-Hochberg FDR correction
+
+**Example**:
+```
+identifiers=TP53%0dMDM2%0dATM%0dCHEK2&species=9606
+```
+
+### 6. PPI Enrichment (`ppi_enrichment`)
+
+**Purpose**: Tests if a network has significantly more interactions than expected by chance.
+
+**Endpoint**: `/api/json/ppi_enrichment`
+
+**Parameters**:
+- `identifiers` (required): List of protein IDs
+- `species`: NCBI taxon ID
+- `required_score`: Confidence threshold
+- `caller_identity`: Application identifier
+
+**Output Format**: JSON with fields:
+- `number_of_nodes`: Proteins in network
+- `number_of_edges`: Interactions observed
+- `expected_number_of_edges`: Expected interactions (random)
+- `p_value`: Statistical significance
+
+**Interpretation**:
+- p-value < 0.05: Network is significantly enriched
+- Low p-value indicates proteins form functional module
+
+**Example**:
+```
+identifiers=TP53%0dMDM2%0dATM%0dCHEK2&species=9606
+```
+
+### 7. Homology Scores (`homology`)
+
+**Purpose**: Retrieves protein similarity/homology scores.
+
+**Endpoint**: `/api/tsv/homology`
+
+**Parameters**:
+- `identifiers` (required): Protein IDs
+- `species`: NCBI taxon ID
+- `caller_identity`: Application identifier
+
+**Output Format**: TSV with homology scores between proteins
+
+**Use cases**:
+- Identifying protein families
+- Paralog analysis
+- Cross-species comparisons
+
+### 8. Version Information (`version`)
+
+**Purpose**: Returns current STRING database version.
+
+**Endpoint**: `/api/tsv/version`
+
+**Output**: Version string (e.g., "12.0")
+
+## Common Species NCBI Taxon IDs
+
+| Organism | Common Name | Taxon ID |
+|----------|-------------|----------|
+| Homo sapiens | Human | 9606 |
+| Mus musculus | Mouse | 10090 |
+| Rattus norvegicus | Rat | 10116 |
+| Drosophila melanogaster | Fruit fly | 7227 |
+| Caenorhabditis elegans | C. elegans | 6239 |
+| Saccharomyces cerevisiae | Yeast | 4932 |
+| Arabidopsis thaliana | Thale cress | 3702 |
+| Escherichia coli K-12 | E. coli | 511145 |
+| Danio rerio | Zebrafish | 7955 |
+| Gallus gallus | Chicken | 9031 |
+
+Full list: https://string-db.org/cgi/input?input_page_active_form=organisms
+
+## STRING Identifier Format
+
+STRING uses Ensembl protein IDs with taxon prefix:
+- Format: `{taxonId}.{ensemblProteinId}`
+- Example: `9606.ENSP00000269305` (human TP53)
+
+**ID Components**:
+- **Taxon ID**: NCBI taxonomy identifier
+- **Protein ID**: Usually Ensembl protein ID (ENSP...)
+
+## Interaction Confidence Scores
+
+STRING provides combined confidence scores (0-1000) based on multiple evidence channels:
+
+### Evidence Channels
+
+1. **Neighborhood (nscore)**: Gene fusion and conserved genomic neighborhood
+2. **Fusion (fscore)**: Gene fusion events across species
+3. **Phylogenetic Profile (pscore)**: Co-occurrence across species
+4. **Coexpression (ascore)**: RNA expression correlation
+5. **Experimental (escore)**: Biochemical/genetic experiments
+6. **Database (dscore)**: Curated pathway/complex databases
+7. **Text-mining (tscore)**: Literature co-occurrence
+
+### Recommended Thresholds
+
+- **150**: Low confidence (exploratory analysis)
+- **400**: Medium confidence (standard analysis)
+- **700**: High confidence (conservative analysis)
+- **900**: Highest confidence (very stringent)
+
+## Output Formats
+
+### Available Formats
+
+1. **TSV**: Tab-separated values (default, best for data processing)
+2. **JSON**: JavaScript Object Notation (structured data)
+3. **XML**: Extensible Markup Language
+4. **PSI-MI**: Proteomics Standards Initiative format
+5. **PSI-MITAB**: Tab-delimited PSI-MI format
+6. **PNG**: Image format (for network visualizations)
+7. **SVG**: Scalable vector graphics (for network visualizations)
+
+### Format Selection
+
+Replace `/tsv/` in URL with desired format:
+- `/json/network` - JSON format
+- `/xml/network` - XML format
+- `/image/network` - PNG image
+
+## Error Handling
+
+### HTTP Status Codes
+
+- **200 OK**: Successful request
+- **400 Bad Request**: Invalid parameters or syntax
+- **404 Not Found**: Protein/species not found
+- **500 Internal Server Error**: Server error
+
+### Common Errors
+
+1. **"No proteins found"**: Invalid identifiers or species mismatch
+2. **"Species required"**: Missing species parameter for large networks
+3. **Empty results**: No interactions above score threshold
+4. **Timeout**: Network too large, reduce protein count
+
+## Advanced Features
+
+### Bulk Network Upload
+
+For complete proteome analysis:
+1. Navigate to https://string-db.org/
+2. Select "Upload proteome" option
+3. Upload FASTA file
+4. STRING generates complete interaction network and predicts functions
+
+### Values/Ranks Enrichment API
+
+For differential expression/proteomics data:
+
+1. **Get API Key**:
+```
+/api/json/get_api_key
+```
+
+2. **Submit Data**: Tab-separated protein ID and value pairs
+
+3. **Check Status**:
+```
+/api/json/valuesranks_enrichment_status?job_id={id}
+```
+
+4. **Retrieve Results**: Access enrichment tables and figures
+
+**Requirements**:
+- Complete protein set (no filtering)
+- Numeric values for each protein
+- Proper species identifier
+
+### Network Customization
+
+**Network Size Control**:
+- `add_nodes=N`: Adds N most connected proteins
+- `limit`: Controls partner retrieval
+
+**Confidence Filtering**:
+- Adjust `required_score` based on analysis goals
+- Higher scores = fewer false positives, more false negatives
+
+**Network Type Selection**:
+- `functional`: All evidence (recommended for pathway analysis)
+- `physical`: Direct binding only (recommended for structural studies)
+
+## Integration with Other Tools
+
+### Python Libraries
+
+**requests** (recommended):
+```python
+import requests
+url = "https://string-db.org/api/tsv/network"
+params = {"identifiers": "TP53", "species": 9606}
+response = requests.get(url, params=params)
+```
+
+**urllib** (standard library):
+```python
+import urllib.request
+url = "https://string-db.org/api/tsv/network?identifiers=TP53&species=9606"
+response = urllib.request.urlopen(url)
+```
+
+### R Integration
+
+**STRINGdb Bioconductor package**:
+```R
+library(STRINGdb)
+string_db <- STRINGdb$new(version="12", species=9606)
+```
+
+### Cytoscape
+
+STRING networks can be imported into Cytoscape for visualization and analysis:
+1. Use stringApp plugin
+2. Import TSV network data
+3. Apply layouts and styling
+
+## Data License
+
+STRING data is freely available under **Creative Commons BY 4.0** license:
+- ✓ Free to use for academic and commercial purposes
+- ✓ Attribution required
+- ✓ Modifications allowed
+- ✓ Redistribution allowed
+
+**Citation**: Szklarczyk et al. (latest publication)
+
+## Rate Limits and Usage
+
+- **Rate limiting**: No strict limit, but avoid rapid-fire requests
+- **Recommendation**: Wait 1 second between calls
+- **Large datasets**: Use bulk download from https://string-db.org/cgi/download
+- **Proteome-scale**: Use web upload feature instead of API
+
+## Related Resources
+
+- **STRING website**: https://string-db.org
+- **Download page**: https://string-db.org/cgi/download
+- **Help center**: https://string-db.org/help/
+- **API documentation**: https://string-db.org/help/api/
+- **Publications**: https://string-db.org/cgi/about
+
+## Troubleshooting
+
+**No results returned**:
+- Verify species parameter matches identifiers
+- Check identifier format
+- Lower confidence threshold
+- Use identifier mapping first
+
+**Timeout errors**:
+- Reduce number of input proteins
+- Split large queries into batches
+- Use bulk download for proteome-scale analyses
+
+**Version inconsistencies**:
+- Use version-specific URLs
+- Check STRING version with `/version` endpoint
+- Update identifiers if using old IDs