Monitoring detergent-mediated solubilization and reconstitution of lipid membranes by isothermal titration calorimetry.
The solubilization and reconstitution of biological or liposomal membranes by detergents and biomolecules with detergent-like properties play a major role for technical applications (e.g., the isolation of membrane proteins) and biological phenomena (of, e.g., amphiphilic peptides). It is therefore important to know and understand the amounts of a given detergent required for the onset and completion of membrane solubilization and the detergent-lipid interactions in general. Lipid-detergent systems can form a variety of aggregate structures, which can be grouped into two pseudophases (lamellae and micelles) so that solubilization can be approximately described as a phase transition. Here we present a protocol for establishing the phase diagram and a detailed thermodynamic description of a lipid-detergent system based on isothermal titration calorimetry (ITC). The protocol can also be used to detect additive-induced membrane destabilization, permeabilization, domain formation and lipid-dependent transitions between rod-like and spherical micelles. A minimal protocol consisting of all sample preparation procedures and a single solubilization experiment can be accomplished within 2 days; a more extensive series comprising both solubilization and reconstitution experiments requires several days to a few weeks, depending on the number of titrations performed.
Heerklotz
Heiko
H
Leslie Dan Faculty of Pharmacy, University of Toronto, 144 College Street, Room 1104, Toronto, Ontario, Canada M5S 3M2. heiko.heerklotz@utoronto.ca
Tsamaloukas
Alekos D
AD
Keller
Sandro
S
D002151:Calorimetry / Q000379:methods*; D003902:Detergents / Q000494:pharmacology*; D008567:Membranes, Artificial; D008823:Micelles; D010713:Phosphatidylcholines / Q000737:chemistry*; D012995:Solubility; D017186:Titrimetry / Q000379:methods; D053835:Unilamellar Liposomes / Q000737:chemistry
D003902:Detergents; D008567:Membranes, Artificial; D008823:Micelles; D010713:Phosphatidylcholines; D053835:Unilamellar Liposomes; C028694:1-palmitoyl-2-oleoylphosphatidylcholine