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Phospholipid phase transitions in homogeneous nanometer scale bilayer discs
Author(s) -
Shaw Andrew W,
McLean Mark A,
Sligar Stephen G
Publication year - 2004
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(03)01400-5
Subject(s) - laurdan , differential scanning calorimetry , vesicle , lipid bilayer , chemistry , phospholipid , nanodisc , bilayer , lipid bilayer phase behavior , phase transition , thermotropic crystal , biophysics , model lipid bilayer , membrane fluidity , phosphatidylcholine , analytical chemistry (journal) , crystallography , membrane , phase (matter) , chromatography , biochemistry , organic chemistry , biology , liquid crystalline , physics , quantum mechanics , thermodynamics
Nanoscale protein supported phospholipid bilayer discs, or Nanodiscs, were produced for the purpose of studying the phase transition behavior of the incorporated lipids. Nanodiscs and vesicles were prepared with two phospholipids, dipalmitoyl phosphatidylcholine and dimyristoyl phosphatidylcholine, and the phase transition of each was analyzed using laurdan fluorescence and differential scanning calorimetry. Laurdan is a fluorescent probe sensitive to the increase of hydration in the lipid bilayer that accompanies the gel to liquid crystalline phase transition. The emission intensity profile can be used to derive the generalized polarization, a measure of the relative amount of each phase present. Differential scanning calorimetry was used to further quantitate the phase transition of the phospholipids. Both methods revealed broader transitions for the lipids in Nanodiscs compared to those in vesicles. Also, the transition midpoint was shifted 3–4°C higher for both lipids when incorporated into Nanodiscs. These findings are explained by a loss of cooperativity in the lipids of Nanodiscs which is attributable to the small size of the Nanodiscs as well as the interaction of boundary lipids with the protein encircling the discs. The broad transition of the Nanodisc lipid bilayer better mimics the phase behavior of cellular membranes than vesicles, making Nanodiscs a ‘native‐like’ lipid environment in which to study membrane associated proteins.