INVESTIGADORES
WILKE Natalia
congresos y reuniones científicas
Título:
Interfacial behaviour of diacylglycerol pyrophosphate and their mixtures with phosphatidic acid at the air-water interface
Autor/es:
A. L. VILLASUSO, N. WILKE, B. MAGGIO, E. MACHADO
Reunión:
Congreso; VII Iberoamerican Congreso of Biophysics; 2009
Resumen:
Diacylglycerol
pyrophosphate (DGPP), a phosphorylated form of phosphatidic acid (PA) found in
plants and yeast but not in mammals, is a minor lipid that
accumulates transiently under various abiotic stresses and during biotic
interactions. DGPP formation may attenuate PA content but DGPP itself
might be a signalling lipid.
In
this work we studied the interfacial behavior of DGPP and their mixture with
palmitoyl oleoyl phosphatidic acid (PA) at the air-water interface at pH 8,
where both lipids are negativelly charged (-2 and -1 respectively). DGPP forms
expanded monolayers that collapse at 35 mN m-1 and 0.64 nm2
with compressibility values between 20 mN m-1 and 60 mN m-1.
At the lift off, the surface potential is 150 mV, corresponding to a molecular
dipole moment perpendicular to the interface of 0.14 D and at collapse, is 350
mV (0.22 D).
At
pH 5, the isotherm is more condensed and collapses at 45 mN m-1 and
0.50 nm2, in agreement with a charge diminution.
The mixture of DGPP with its precursor PA forms non ideal mixtures, homogeneous at the
microscopic level (0.06 mm2); the interaction among these lipids
leads to a diminution of the mean molecular area and to an increase of the
compressibility at all lateral pressures. The excess free energy of compression
are negative (-1500 to -2100 J mol-1) for all the proportions
analyzed. The dipole moment perpendicular to the interface of the molecules in
the mixtures at high lateral pressures is similar to the value of pure PA.
In summary, the favorable interaction of PA and DGPP,
leading to an increase of the film packing, may represent a structural
signalling event involving DGPP.