Link used in a conjugation to distance the substrate from the active species that otherwise would have its activity affected by steric or other influences.
Source:
PAC, 2022, 94, 559. 'Terminology and the naming of conjugates based on polymers or other substrates (IUPAC Recommendations 2021)' on page 563 (https://doi.org/10.1515/pac-2020-0502)