Impact of sphingomyelin acyl chain (16:0 vs 24:1) on the interfacial properties of Langmuir monolayers?

ROMINA F. VAZQUEZ; M. ANTONIETA DAZA MILLONE; PAVINATTO, FELIPPE J.; M. LAURA FANANI; OLIVEIRA JR., OSVALDO N.,; MARIA ELENA VELA; SABINA MATÉ

Congreso; XLVII Reunión Anual de la Sociedad Argentina de Biofísica.; 2018

Impact of sphingomyelin acyl chain (16:0 vs 24:1) on the interfacial properties of Langmuir monolayers Vázquez Ra, Daza Millone MAb, Pavinatto FJc, Fanani MLd, Oliveira ONc, Vela MEb, Maté Sa a - Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), CCT- La Plata, CONICET. Facultad de Ciencias Médicas. Universidad Nacional de La Plata. b - Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), CCT- La Plata, CONICET. Facultad de Ciencias Exactas, Universidad Nacional de La Plata. c - São Carlos Institute of Physics, University of São Paulo d - Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), CONICET. Departamento de Química Biológica Ranwel Caputto, Facultad de Cs. Químicas, Universidad Nacional de Córdoba.Sphingomyelin (SM) and related sphingolipids are believed to have important functional roles on membrane domain formation, e.g. for the Cholesterol (Chol)rich liquid-ordered ( Lo ) phase. Notwithstanding, N-nervonoyl-SM (24:1-SM)?the most common unsaturated SM natural species?is able to prevent phase segregation. In this study, Polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS) was applied to investigate the conformational properties and intermolecular interactions in 16:0 vs 24:1-SM monolayers and their mixtures with 1,2-Dioleoyl-sn-glycero-3-phosphocholine (DOPC) and Chol (DOPC/SM/Chol 2:1:1). From the results we inferred that the cis double bond (Δ15) in 24:1-SM molecule diminishes intermolecular H-bonding and chain packing density compared to that of 16:0-SM. In ternary mixtures containing 16:0-SM, the relative intensity of the two components of the Amide I band reflected changes in the Hbonding network due to SM-Chol interactions. In contrast, the contribution of the main components of the Amide I band in DOPC/24:1-SM/Chol remained as in 24:1SM monolayers, with a larger contribution of the non-H-bonded component. The most interesting feature in these ternary films is that the C=O stretching mode of DOPC appeared with an intensity similar to that of SM Amide I band in DOPC/16:0SM/Chol monolayers (a two-phase [ Lo / Le ] system), whereas an extremely low intensity of the C=O band was detected in DOPC/24:1-SM/Chol monolayers (single Le phase). This is evidence that the unsaturation in 24:1-SM affected not only the conformational properties of acyl chains but also the orientation of the chemical groups at the air/water interface. The physical properties and overall H-bonding ability conferred by 24:1-SM may have implications in cell signaling and binding of biomolecules. 90