Albumiinin

Albumiinin, in Finnish usage, refers to albumin, the major water-soluble protein in blood plasma of vertebrates. Produced mainly by hepatocytes in the liver, it is secreted into the circulatory system and constitutes a large fraction of plasma proteins. In humans, the serum albumin molecule has a molecular weight of about 66.5 kDa and a length of roughly 585 amino acids, and it exists as a single polypeptide chain organized into three homologous domains (I–III) with two subdomains each. A free thiol group at cysteine-34 provides antioxidant properties and serves as a site for redox reactions.

Primary functions include maintaining colloid osmotic pressure, which helps retain fluid within blood vessels, and transporting a wide range of substances, including fatty acids, bilirubin, hormones, minerals, and many drugs. The protein also acts as a reservoir for amino acids and participates in pH buffering and antioxidant defense. Its ligand-binding capacity and conformational flexibility enable it to modulate the pharmacokinetics of numerous medications.

Synthesis occurs in the liver, with secretion into plasma; the typical half-life in humans is about 19 days. Albumin levels are influenced by nutrition, liver function, kidney function, and inflammatory status. Hypoalbuminemia can indicate malnutrition, liver disease, nephrotic syndrome, or protein-losing enteropathies; dehydration can cause apparent hyperalbuminemia.

Clinically, albumin solutions are used as plasma expanders in certain settings. In laboratory contexts, albumin from bovine serum (BSA) is widely used as a standard, calibrant, or blocking agent in assays.