title: Covalent complexes between serum albumin and 7-hydroxycoumarin-4-acetic acid: synthesis and applications in the spectrophotometric detection of long-chain fatty acids.
abstract: Using a hydrophobic 8-aminooctanoic acid cross-linker, the pH-indicator dye 7-hydroxycoumarin-4-acetic acid (7-HCA) is covalently bound to bovine serum albumin (BSA) at the positions of reactive amino groups. A highly stable and water-soluble complex (BSA-HCA) with a 1:4 molar stoichiometry is synthesized. Appearance of a strong absorption band at gamma max = 372 nm is associated to ionization of the 7-HCA chromophore when it is transferred from water into a basic microenvironment on the BSA surface. This particular surface site is related to the region(s) for high-affinity binding of long-chain fatty acids (FA). BSA-HCA responds to binding of FA (14-20 carbons) with immediate spectral changes and a decrease in 372 nm absorption. BSA-HCA provides an indicator-protein having a range of practical applications for the quantitative determination of long-chain FA in biochemical studies. The lower detection limit in a spectrophotometric method is approximately 1 microM FA. BSA-HCA is usable both in various buffers and in the presence of detergents such as n-octylglucoside, Triton X-100 and CHAPS. A novel method for continuous assay of phospholipase A2 activity with BSA-HCA and a mixed phosphatidylcholine/CHAPS micellar substrate is reported.
authors.affiliation: Department of Medical Biochemistry and Genetics, Panum Institute, University of Copenhagen, Denmark.
authors.forename: E J
authors.initials: EJ
authors.lastname: Demant
mesh_terms: D000085:Acetates / Q000737:chemistry*; D002210:Caprylates / Q000737:chemistry; D003374:Coumarins / Q000737:chemistry*; D003432:Cross-Linking Reagents; D005227:Fatty Acids / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D019301:Oleic Acid / Q000378:metabolism; D010741:Phospholipases A / Q000032:analysis; D054467:Phospholipases A2; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D013053:Spectrophotometry / Q000379:methods*
chemical_list: D000085:Acetates; D002210:Caprylates; D003374:Coumarins; D003432:Cross-Linking Reagents; D005227:Fatty Acids; D007202:Indicators and Reagents; C046323:omega-aminocaprylic acid; D012710:Serum Albumin, Bovine; D019301:Oleic Acid; C102522:7-hydroxycoumarin-4-acetic acid; D010741:Phospholipases A; D054467:Phospholipases A2