title: Binding of perfluorocarboxylates to serum albumin: a comparison of analytical methods.
abstract: Perfluorochemicals are globally pervasive contaminants that are persistent, bioaccumulative, and toxic. Perfluorocarboxylic acids (PFCAs) with 8-13 carbons accumulate in the liver and blood of aquatic organisms; PFCA-protein interactions may explain this accumulation pattern. Here, the interactions between PFCAs with 8-11 carbons and serum albumin are examined using three experimental approaches: surface tension titrations, (19)F NMR spectroscopy, and fluorescence spectroscopy. Surface tension titrations indicate complex formation at high (mM) PFCA concentrations. Secondary association constants ranging from 10(2) to 10(4) M(-1) were determined from (19)F NMR titrations at high PFCA:albumin mole ratios. Fluorescence measurements indicate that PFCA-albumin interactions alter the protein conformation at low PFCA:albumin mole ratios (up to 5:1) and suggest two binding classes with association constants around 10(5) and 10(2) M(-1). While (19)F NMR and fluorescence provide both qualitative and quantitative information about PFCA-albumin interactions, surface tension provides only qualitative information. Limitations associated with instrumentation and methods require high PFCA concentrations in both surface tension and (19)F NMR experiments; in contrast, fluorescence allows for analysis of a wider range of PFCA concentrations and PFCA:albumin mole ratios. Results from this study indicate that fluorescence, though an indirect method, offers a more comprehensive picture of the nature of PFCA-albumin interactions.
authors.affiliation: Department of Chemistry, Union College, Schenectady, New York 12308, USA. macmanul@union.edu
authors.forename: Laura A
authors.initials: LA
authors.lastname: MacManus-Spencer
authors.forename: Monica L
authors.initials: ML
authors.lastname: Tse
authors.forename: Paul C
authors.initials: PC
authors.lastname: Hebert
authors.forename: Heather N
authors.initials: HN
authors.lastname: Bischel
authors.forename: Richard G
authors.initials: RG
authors.lastname: Luthy
mesh_terms: D000818:Animals; D002210:Caprylates / Q000737:chemistry; D002417:Cattle; D003652:Decanoic Acids / Q000737:chemistry; D005466:Fluorocarbons / Q000737:chemistry*; D006801:Humans; D007850:Lauric Acids / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D011485:Protein Binding; D012709:Serum Albumin / Q000737:chemistry*; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D013050:Spectrometry, Fluorescence / Q000379:methods*
chemical_list: D002210:Caprylates; D003652:Decanoic Acids; D005466:Fluorocarbons; D007850:Lauric Acids; D012709:Serum Albumin; D012710:Serum Albumin, Bovine; C036567:perfluorodecanoic acid; C023036:perfluorooctanoic acid; C522391:perfluorododecanoic acid