Behavior of sphingomyelins with very long chain fatty acids in bilayers and monolayers.

PEÑALVA, D.A.; FANANI, M.L.; MAGGIO, B.; AVELDAÑO, M. I.; ANTOLLINI, S.S.

Mendoza

Congreso; XLVIII Reunión Annual de la Sociedad Argentina de Investigaciones en Bioquímica y Biología Molecular; 2012

BEHAVIOR OF SPHINGOMYELINS WITH VERY LONG CHAIN FATTY ACIDS IN BILAYERS AND MONOLAYERS Peñalva DA1, Fanani ML2, Maggio B2, Aveldaño MI1, Antollini SS1 1 INIBIBB, CONICET-UNS, Bahía Blanca, and 2CIQUIBIC, UNC-CONICET, Córdoba, Argentina. E-mail: dpenalva@criba.edu.ar Very long-chain (C24 to C36) polyunsaturated fatty acids (VLCPUFA) are important acyl groups of sphingomyelin (SM) and ceramides (Cer) of mammalian spermatozoa. Our project aims at establishing peculiarities of their biophysical properties and modes of interaction with other lipids in sperm membranes. In this study, rat testicular SM were separated into fractions enriched in nonhydroxy and 2-hydroxy VLCPUFA (N-V and H-V SM, respectively), and individual molecular species of SM with different N-V and H-V by combining different chromatographic techniques. In liposomes prepared from each of these fractions and species, thermotropic properties were studied by fluorescence spectroscopy. Two probes that localize at different depths in the bilayer (DPH, Laurdan) were used to study the influence of number of double bonds, fatty acid chain length, and presence of the 2-OH group. In ternary systems with phosphatidylcholine and cholesterol, N-V and H-V SMs did not segregate together with cholesterol, as saturated SMs do. In Langmuir monolayers, surface pressure, surface potential, and reflectivity of p-polarized light were measured to determine average molecular area (degree of packing) and thickness in membranes. SM species containing N-V and H-V contrasted in all biophysical properties measured with those of the most common saturated (e.g., 16:0) SM.