Role of phase coexistence and
composition of ternary liposomes containing cholesterol and ceramide on spontaneous
curvature and structural stability.
Giudice F., Maggio B., Fanani M.L.,
Centro de Investigaciones en Química Biológica
de Córdoba (CIQUIBIC), Departamento de Química
Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba,Haya
de la Torre y Medina Allende, Ciudad Universitaria, X5000HUA, Córdoba,
Argentina.
Lipid dispersion of
POPC / Chol / Cer in a wide range of relative composition were prepared by the
traditional method of extrusion and compared with liposomes formed by the
“Rapid Solvent Exchange” method (RSE) [1], which allows lipid vesicles to adopt
its spontaneous curvature, without external influences such as filtration or
sonication. Thus, spontaneous curvatures of the ternary dispersions were evaluated
and related to the different phase states characterized in these mixtures [2].
The data shows that, as we move from a fluid phase to the fluid and gel phases coexistence
regions, the liposomes showed a higher polydispersity in diameter, which
appears to depend on the composition of the fluid phase that in turn, depends
on the relative cholesterol/ceramide ratio.
This work was
supported by: FONCyT, CONICET and SECyT-UNC
[1] Jeffrey
T.Buboltz, Gerald W.Feigenson, A novel strategy for the preparation of
liposomes: rapid solvent exchange, Biochi.Biophys. Acta 1417 (1999) 232-245.
[2] Bruno M. Castro,
Liana C. Silva, Alexander Fedorov, Rodrigo F.M. de Almeida, and Manuel Prieto,
Cholesterol-rich fluid membranes solubilize ceramida domains, The journal
of biological chemistry VOL 284,NO.34
pp.22978-22987.
Surface behaviour of sphingomyelines with very long
chains (C28-C32) PUFAs and their interaction with premixed or enzymatically
generated ceramides
Peñalva DA1, Wilke N2, Maggio B2,
Aveldaño MI1, Fanani ML2
1INIBIBB,
CONICET-UNS, Bahía Blanca, 2CIQUIBIC, UNC-CONICET, Córdoba,
Argentina.
Molecular
species of sphingomyelin (SM) with nonhydroxy (n) and 2-hydroxy (h) very
long-chain polyunsaturated fatty acids (n- and h- 28:4, 30:5 and 32:5) abound
in rat spermatogenic cells and spermatozoa. These SMs are exclusively located
on the sperm head, where they are converted into the corresponding Cer by
sphingomyelinase after completion of the acrosomal reaction. The aim of this
study was to gain some insight into the surface properties of this unique type
of sphingolipids and how such properties change by the SM ® Cer conversion. SM and Cer species were isolated by
HPLC [1] and organized in Langmuir films, alone and in SM/Cer mixtures. Compression
isotherms for all six SMs under study were compatible with a liquid-expanded
state and showed large mean molecular areas. Only the longest SMs (n- and h-32:5
SM) underwent phase transition upon cooling. h-28:4 SM show typical general properties whereas h-28:4 Cer exhibited an easily compressible
liquid condensed phase [2] which may results from its higher conformational
freedom in such phase. In premixed and enzymatically generated h-28:4 SM /
h-28:4 Cer films, Cer-rich domains with a high incorporation of SM were formed.
In conclusion, while the SMs from sperm behave in a regular way, the corresponding Cers show
atypical properties that may be relevant for the structural rearrangement occurring
in the acrosome-reacted sperm membrane.
This work was supported by FONCyT, CONICET, SECyT-UNC
and SECyT-UNS.
1-
D.A. Peñalva, et al, J. Lipid Res. (2013) 54:2225-35.
2-
D.A. Peñalva, et al, Biochim Biophys Acta
(2013), submitted.
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