Boundary lipid in proteolipid—lipid recombinants revealed by fluorescence energy transfer and spin probe study

Thermotropic Phase Transition in Soluble Nanoscale Lipid Bilayers

“…In this case it would be necessary to conclude that the boundary lipid layer undergoes the same, or a very similar, thermotropic transition, at least in a dynamic sense, because Laurdan fluorescence probes the relaxation properties of the polar molecules in the time window corresponding to the lifetime of the excited state of the naphthalene fluorophore. Although this possibility cannot be excluded on the basis of our data, there is much evidence against this assumption. ,,− More probable is a preferential distribution of Laurdan into the bulk lipid fraction, at least during the phase transition and at higher temperatures. The equal distribution of the Laurdan probe between the bulk and boundary lipid fractions at low temperatures cannot be excluded because both lipid phases may have relatively low mobility despite the structural perturbation and the lack of cooperative melting for boundary lipids as compared to unperturbed lipid bilayer.…”

“…Although this possibility cannot be excluded on the basis of our data, there is much evidence against this assumption. 68,76,[90][91][92][93][94][95] More probable is a preferential distribution of Laurdan into the bulk lipid fraction, at least during the phase transition and at higher temperatures. The equal distribution of the Laurdan probe between the bulk and boundary lipid fractions at low temperatures cannot be excluded because both lipid phases may have relatively low mobility despite the structural perturbation and the lack of cooperative melting for boundary lipids as compared to unperturbed lipid bilayer.…”