Proteinkoblede

Proteinkoblede describes substances or molecules that are bound to proteins, typically in biological fluids or tissues. In biochemistry and pharmacology, the protein-bound fraction is distinguished from the free fraction, and the two forms can have different biological activities and fates.

Binding to proteins occurs mainly through non-covalent interactions such as hydrophobic contacts, ionic bonds and hydrogen bonds. Serum albumin and various transport proteins are common binding partners in circulation, while tissues can harbor protein–ligand complexes as well. In some cases, covalent attachment may occur, but this is less common for small-molecule ligands. The protein-bound reservoir often serves to release the substance gradually, influencing distribution, duration of action and clearance.

In pharmacology, the extent of protein binding affects the availability of a drug to interact with its target. A high degree of binding reduces the free, active concentration in the bloodstream and can modify intensity and onset of effects. Drug–drug interactions frequently arise when two compounds compete for the same binding sites on a protein such as albumin, potentially altering free drug levels. Endogenous substances like bilirubin and fatty acids are also frequently found in protein-bound form, influencing their transport and metabolism.

In research and clinical practice, measuring the protein-bound fraction helps characterize pharmacokinetics, dosing needs, and potential interactions. Methods such as equilibrium dialysis and ultrafiltration separate bound from unbound fractions for analysis. The concept also intersects with areas like proteomics and nanomedicine, where protein binding can affect assay results and the behavior of therapeutic agents.