| Code | Name | Deposits | Targets | Ligand Type |
|---|---|---|---|---|
| SO3 | sulfite ion | 1 | 1 | crystallization |
| SO4 | sulfate | 48 | 43 | other |
| SO4 | sulfate | 8 | 8 | biological |
| SO4 | sulfate | 200 | 148 | crystallization |
| SUC | sucrose | 7 | 7 | crystallization |
| SUC | sucrose | 2 | 2 | other |
| SIN | succinic acid | 7 | 7 | crystallization |
| SIN | succinic acid | 1 | 1 | biological |
| SIN | succinic acid | 2 | 2 | other |
| CSZ | s-selanyl cysteine | 1 | 1 | modified residue |
| SPM | spermine | 2 | 1 | biological |
| SIS | sisomicin | 2 | 2 | biological |
| CSO | S-HYDROXYCYSTEINE | 2 | 2 | biological |
| CSO | S-HYDROXYCYSTEINE | 2 | 2 | crystallization |
| CSO | S-HYDROXYCYSTEINE | 3 | 3 | modified residue |
| S3P | shikimate-3-phosphate | 4 | 3 | biological |
| MSO | selenomethionine selenoxide | 1 | 1 | modified residue |
| CAF | s-dimethylarsinoyl-cysteine | 1 | 1 | modified residue |
| SAM | s-adenosylmethionine | 5 | 2 | biological |
| SAM | s-adenosylmethionine | 1 | 1 | crystallization |