Protein to which a specific ligand or hapten is conjugated.
Unlabeled protein introduced into an assay at relatively high concentrations which distributes in a fractionation process in the same manner as labeled protein analyte, present in very low concentrations.
Protein added to prevent non-specific interaction of reagents with surfaces, sample components, and each other.
Protein found in cell membranes, which facilitates transport of a ligand across the membrane.
Source: PAC, 2004, 76, 1033. 'Glossary of terms used in toxicokinetics (IUPAC Recommendations 2003)' on page 1043 (https://doi.org/10.1351/pac200476051033)