| ERTAS | extended reticulo-thalamic activating system |
|---|---|
| EXAFS | extended x-ray absorption fine structure |
| EXELFS | extended electron-loss line fine structure |
| Fc' | a fragment of an immunoglobulin molecule produced by papain digestion |
| Fd | the amino-terminal portion of the heavy chain of an immunoglobulin molecule; ferredoxin |