Effect of amyloid ß-peptide on the fluidity of phosphatidylcholine membranes: Uses and limitations of diphenylhexatriene fluorescence anisotropy.

Biochimica et biophysica acta

PubMedID: 25497764

Suzuki M, Miura T. Effect of amyloid ß-peptide on the fluidity of phosphatidylcholine membranes: Uses and limitations of diphenylhexatriene fluorescence anisotropy. Biochim Biophys Acta. 2014;.
There is accumulating evidence that peptide-induced perturbations in the order and dynamics of cellular membranes may play a role in the neurotoxicity of amyloid ß-peptide (Aß). Several studies have reported that Aß decreases fluidity of membranes based on an Aß-induced increase in the fluorescence anisotropy of diphenylhexatriene (DPH). However, the effect of Aß on the membrane fluidity is still a subject of controversy, because other studies that employed pyrene as a fluorescent probe have shown that Aß has the opposite effect. To reveal the reason for this discrepancy, we have examined the effect of Aß on the fluidity of phosphatidylcholine membranes using spectroscopic methods. The fluorescence anisotropy of DPH is dramatically increased on addition of Aß to DPH-containing phosphatidylcholine membranes. However, Aß does not affect the Raman spectrum of the membrane, which is sensitive to the packing order of the hydrocarbon chains of lipids. We have also found that circular dichroism (CD) bands of DPH appear during incubation of DPH-containing membranes with Aß, whereas DPH is an achiral molecule. The observed CD bands of DPH are induced by a chiral environment of Aß but not by that of the lipids, because positive CD bands appear regardless of the d/l-chirality of phosphatidylcholine. The findings obtained from CD measurements provide evidence that DPH molecules translocate from the membrane to Aß. The peptide-mediated extraction of DPH from the membrane may cause changes in the fluorescence anisotropy of DPH, even though Aß does not affect the fluidity of membranes.