Ultraviolet-circular dichroism spectroscopy and potentiometric study of the interaction between human serum albumin and sodium perfluorooctanoate.
The interaction of a fluorinated surfactant, sodium perfluorooctanoate, with human serum albumin (HSA) has been investigated by a combination of ultraviolet-circular dichroism (UV-CD) spectroscopy and potentiometry (by a home-built ion-selective electrode) techniques to detect and characterize the conformational transitions of HSA. By using difference spectroscopy, the transition was followed as a function of temperature, and the data were analyzed to obtain the parameters characterizing the thermodynamics of unfolding. The results indicate that the presence of surfactant drastically changes the melting unfolding, acting as a structure stabilizer and delaying the unfolding process. Potentiometric measurements were used to determine the binding isotherms and binding capacity for this system. The isotherm shows a high affinity of surfactant molecules for HSA. The average number of surfactant molecules absorbed per protein molecule (at 28 mM of surfactant concentration) was found to be approximately 900, about 6 g of surfactant per gram of protein. The shape of the binding capacity curve and the relation between binding capacity and extend of cooperativity were examined. From these analysis, the values of g (number of ligand-binding sites), KH (Hill binding constant), and nH (Hill coefficient) were determined.
Messina
Paula
P
Grupo de Ciencia de Superficies y Coloides, Departamento de Química, Universidad Nacional del Sur, 8000 Bahía Blanca, Argentina.
Prieto
Gerardo
G
Dodero
Verónica
V
Ruso
Juan M
JM
Schulz
Pablo
P
Sarmiento
Félix
F
D002210:Caprylates / Q000737:chemistry / Q000378:metabolism*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002942:Circular Dichroism; D005466:Fluorocarbons / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008433:Mathematics; D008970:Molecular Weight; D011199:Potentiometry; D011485:Protein Binding; D011487:Protein Conformation; D011489:Protein Denaturation; D017433:Protein Structure, Secondary; D012709:Serum Albumin / Q000737:chemistry / Q000378:metabolism*; D012996:Solutions; D013056:Spectrophotometry, Ultraviolet; D013501:Surface-Active Agents / Q000737:chemistry; D013696:Temperature; D013816:Thermodynamics; D014867:Water / Q000737:chemistry
D002210:Caprylates; D005466:Fluorocarbons; D012709:Serum Albumin; D012996:Solutions; D013501:Surface-Active Agents; D014867:Water; C023036:perfluorooctanoic acid