Biophysical Society Thematic Meeting| Lima 2019

Revisiting the Central Dogma of Molecular Biology at the Single-Molecule Level

Poster Abstracts

51-POS Board 51 THE IMPACT OF OXIDIZED POPC DERIVATIVES ON LIPID BILAYER HYDRATION AND FLUIDITY: INSIGHTS FROM STEADY-STATE AND TIME- RESOLVED FLUORESCENCE METHODOLOGIES Gustavo Scanavachi 1,2 ; Ana Melo 2 ; Ana Coutinho 2,3 ; Aleksander Fedorov 2 ; Manuel Prieto 2 ; Rosagela Itri 1 ; 1 Laboratório de Cristalografia, Departamento de Física Aplicada, Instituto de Física, Universidade de São Paulo, São Paulo, Brazil 2 Centro de Química-Física Molecular and Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal 3 Departamento de Química e Bioquimica, Faculdade de Ciências, Universidade de Lisboa, Lisboa, Portugal The presence of oxidized lipids in natural membranes plays a crucial role in several biological dysfunctions, such as cardiovascular disease, Alzheimer’s disease and Type II diabetes. Despite intensive study, the impact of oxidized lipids in the membrane physical properties remains elusive. Here,the influence of oxidized lipids obtained by oxidation of POPC (POPC-OOH, PAzePC and POVPC) on the properties of mimetic membranes of POPC was investigated by steady-state and time-resolved fluorescence techniques,at 23 and 37 o C. Remarkably, our results show a decrease in the fluorescence lifetime of TMA-DPH (a lipid/water interface probe) with increasing of mol% of POPC-OOH,reporting an increase in water penetration at the membrane interface. Moreover, from time-resolved anisotropy data of TMA-DPH,an increase in the average rotational diffusion time,<φ>,of the probe was observed, pointing out to an increase in the microviscosity, η,of the environment around the probe. This is compatible with the location of – OOH group near the carbonyl/polar-head region implying a decrease in free volume for probe rotation and a concomitant increase in the surface area of oxidized membranes. Interestingly, a decrease in the limiting anisotropy, r oo , of TMA-DPH was also observed, meaning that the probe rotational dynamics is confined within a larger wobbling cone in the presence of POPC-OOH. These results are also supported by time-resolved emission spectra (TRES) analysis of Laurdan to evaluate the dipolar relaxation in the same vicinity as TMA-DPH. Furthermore, the presence of the truncated PAzePC and POVPC also increased the hydration degree and the area per lipid at the membrane interface,according to the sequence: POVPC>PAzePC>POPC-OOH. These findings are again supported by Generalized Polarization (GP) and TRES analysis of Laurdan. Finally, PAzePC and POVPC only have a significant impact on the microviscosity values at 37 o C but not at 23 o C, suggesting that their truncated chains can only efficiently approach the membrane interface at higher temperatures.

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