Faculty of Physics - University of Bucharest

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FACULTY OF PHYSICS

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Conference: Bucharest University Faculty of Physics 2018 Meeting

Section: Biophysics; Medical Physics

Title:

The effect of folic acid on DPPC liposomes

Authors:

Mirela CRISTEA (1), Bogdan ZORILĂ (1,2), Mihaela BACALUM (2), Claudia G. CHILOM (1)

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Affiliation:

1) Department of Electricity, Solid Physics and Biophysics, Faculty of Physics, University of Bucharest, Romania

2) Department of Life and Environmental Physics, “Horia Hulubei” National Institute of Physics and Nuclear Engineering, Măgurele, Romania

E-mail

claudiafir@gmail.com

Keywords:

Folic acid, dipalmitoylphosphatidylcholine (DPPC), laurdan, liposome fluidity

Abstract:

Lipid organization in liposomal membranes can be affected by the presence of bioactive components, such as folic acid, a water-soluble vitamin B. In this study, the interaction of folic acid with dipalmitoylphosphatidylcholine (DPPC) liposomes was followed by UV-Vis spectroscopy, steady state, and time resolved fluorimetry. The absorption spectrum of DPPC liposomes was significantly affected by the presence of folic acid, as an indication that the lipid organisation was altered by the folic acid insertion into the liposomal membrane. Fluorescence emission of folic acid increased in the presence of liposome suspension, suggesting that the fluorescent areas of folic acid molecules are no longer exposed to the solvent but interact with DPPC liposomes. Membrane fluidity changes, induced by folic acid - liposomes interactions, were highlighted by laurdan fluorescent properties. Thus, the general polarization, GP, and relative area, ΔSR profiles confirmed the membrane tendency to become rigid at low temperature and fluid at high temperature, where a small number of solvent molecules are present at the membrane interface and thus, the solvent relaxation is manifested. Folic acid partial insertion into the outer liposome layer had not affected the fluidity of DPPC liposomal membranes. Time resolved fluorescence experiments confirm the dynamics of the folic acid molecules in the liposomal membrane. The results may be used in further studies concerning the fluidity of natural membranes.

References:

1. Bacalum M., Zorilă B.l, Radu M. Fluorescence spectra decomposition by asymmetric functions: Laurdan spectrum revisited, Anal Biochem., 440(2):123-129, 2013

2. Zorilă B., Bacalum M., Popescu A. I., Radu M. Log-normal deconvolution of laurdan fluorescence spectra-a tool to assess lipid membrane fluidity, Romanian Reports in Physics, 68(2):702-712, 2016

Acknowledgement:

The work was accomplished with the financial support of the Romanian National Authority for Scientific Research, CNDI-UEFISCDI. Project number: PN 18090202.