title: Atypical surface behavior of ceramides with nonhydroxy and 2-hydroxy very long-chain (C28-C32) PUFAs.
abstract: Unique species of ceramide (Cer) with very-long-chain polyunsaturated fatty acid (VLCPUFA), mainly 28-32 carbon atoms, 4-5 double bonds, in nonhydroxy and 2-hydroxy forms (n-V Cer and h-V Cer, respectively), are generated in rat spermatozoa from the corresponding sphingomyelins during the acrosomal reaction. The aim of this study was to determine the properties of these sperm-distinctive ceramides in Langmuir monolayers. Individual Cer species were isolated by HPLC and subjected to analysis of surface pressure, surface potential, and Brewster angle microscopy (BAM) as a function of molecular packing. In comparison with known species of Cer, n-V Cer and h-V Cer species showed much larger mean molecular areas and increased molecular dipole moments in liquid expanded phases, which suggest bending and partial hydration of the double bonded portion of the VLCPUFA. The presence of the 2-hydoxyl group induced a closer molecular packing in h-V Cer than in their chain-matched n-V Cer. In addition, all these Cer species showed liquid-expanded to liquid-condensed transitions at room temperature. Existence of domain segregation was confirmed by BAM. Additionally, thermodynamic analysis suggests a phase transition close to the physiological temperature for VLCPUFA-Cers if organized as bulk dispersions.
authors: Instituto de Investigaciones Bioquímicas de Bahía Blanca (INIBIBB), Universidad Nacional del Sur and Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), 8000 Bahía Blanca, Argentina.
authors: Daniel A
authors: DA
authors: Peñalva
authors: Instituto de Investigaciones Bioquímicas de Bahía Blanca (INIBIBB), Universidad Nacional del Sur and Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), 8000 Bahía Blanca, Argentina.
authors: Gerardo M
authors: GM
authors: Oresti
authors: Departamento de Química Biológica, Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), Facultad de Ciencias Químicas, Universidad Nacional de Córdoba and CONICET, 5000 Córdoba, Argentina.
authors: Fernando
authors: F
authors: Dupuy
authors: Instituto de Investigaciones Bioquímicas de Bahía Blanca (INIBIBB), Universidad Nacional del Sur and Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), 8000 Bahía Blanca, Argentina.
authors: Silvia S
authors: SS
authors: Antollini
authors: Departamento de Química Biológica, Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), Facultad de Ciencias Químicas, Universidad Nacional de Córdoba and CONICET, 5000 Córdoba, Argentina.
authors: Bruno
authors: B
authors: Maggio
authors: Instituto de Investigaciones Bioquímicas de Bahía Blanca (INIBIBB), Universidad Nacional del Sur and Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), 8000 Bahía Blanca, Argentina.
authors: Marta I
authors: MI
authors: Aveldaño
authors: Departamento de Química Biológica, Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), Facultad de Ciencias Químicas, Universidad Nacional de Córdoba and CONICET, 5000 Córdoba, Argentina. Electronic address: lfanani@fcq.unc.edu.ar.
authors: María L
authors: ML
authors: Fanani
mesh_terms: D000818:Animals; D002518:Ceramides / Q000737:chemistry* / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D005231:Fatty Acids, Unsaturated / Q000737:chemistry / Q000378:metabolism*; D008297:Male; D044367:Phase Transition; D051381:Rats; D013094:Spermatozoa / Q000378:metabolism*; D013499:Surface Properties; D013816:Thermodynamics
chemical_list: D002518:Ceramides; D005231:Fatty Acids, Unsaturated
keywords: 2-Hydroxy fatty acids; 2-hydroxy VLCPUFA; BAM; Brewster angle microscopy; Cer; Cs(−1); L; LC; LE; Langmuir monolayers; MMA; S; SM; Sphingolipids; Th; Two dimensional phase transitions; V; VLCPUFA; ceramide; compressibility modulus; dipole moment perpendicular to the interface; h-V; liquid-condensed; liquid-expanded; mean molecular area; n-V; nonhydroxy VLCPUFA; semi-empirical average molecular length; semi-empirical film thickness; semi-empirical molecular volume; solid phase; sphingomyelin; surface potential; surface pressure; transition pressure; very long chain polyunsaturated fatty acid; ΔV; μ(⊥); π; π(t)