Thermodynamic and Structural Changes Associated with the Interaction of a Dirhamnolipid Biosurfactant with Bovine Serum Albumin

• Published in: Langmuir Vol. 24; no. 13; pp. 6487 - 6495
• Main Authors: Sánchez, Marina, Aranda, Francisco J, Espuny, María J, Marqués, Ana, Teruel, José A, Manresa, Ángeles, Ortiz, Antonio
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.07.2008
• Subjects: Animals; Calorimetry; Cattle; Chemistry; Colloidal state and disperse state; Colloids: Surfactants and Self-Assembly, Dispersions, Emulsions, Foams; Exact sciences and technology; General and physical chemistry; Glycolipids - biosynthesis; Glycolipids - chemistry; Molecular Structure; Protein Denaturation; Pseudomonas aeruginosa; Pseudomonas aeruginosa - chemistry; Pseudomonas aeruginosa - metabolism; Serum Albumin, Bovine - chemistry; Spectroscopy, Fourier Transform Infrared; Surface physical chemistry; Surface-Active Agents - chemistry; Temperature; Thermodynamics; Binding; Differential scanning calorimetry; Correlation; Stability; Bovine; Serum albumin; Protein; Infrared spectrometry; Thermodynamics; Vertebrata; Mammalia; Heating; Affinity; Surface tension; Artiodactyla; Monomer; Structure; Physicochemical properties; Ungulata
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la800636s

The interaction of a dirhamnolipid biosurfactant secreted by Pseudomonas aeruginosa with bovine serum albumin was studied by means of various physical techniques. Binding of the biosurfactant to bovine serum albumin was first characterized by isothermal titration calorimetry, showing that one or two molecules of dirhamnolipid, in the monomer state, bound to one molecule of the protein with high affinity. These results were confirmed by surface tension measurements in the absence and presence of bovine serum albumin. As seen by differential scanning calorimetry, dirhamnolipid shifted the temperature of the thermal unfolding of bovine serum albumin toward higher values, thus increasing the stability of the protein on heating. The impact of dirhamnolipid on the structure of the native protein was low, since most of the secondary structure remained unaffected upon interaction with the biosurfactant, as shown by FTIR spectroscopy. However, 2D correlation infrared spectroscopy indicated that the sequence of temperature-induced structural changes in native bovine serum albumin was modified by the presence of the biosurfactant. The consequences of these results in relation to possible applications of these dirhamnolipid biosurfactants for protein studies are discussed.