Impact of sphingomyelin acyl chain (16:0 vs 24:1) on the interfacial properties of Langmuir monolayers: a PM-IRRAS study

M. ANTONIETA DAZA MILLONE; OSVALDO N. OLIVEIRA JR; ROMINA F. VÁZQUEZ; MARÍA L. FANANI; SABINA M. MATÉ; FELIPPE J. PAVINATTO; MARÍA E. VELA; M. ANTONIETA DAZA MILLONE; OSVALDO N. OLIVEIRA JR; ROMINA F. VÁZQUEZ; MARÍA L. FANANI; SABINA M. MATÉ; FELIPPE J. PAVINATTO; MARÍA E. VELA

COLLOIDS AND SURFACES B-BIOINTERFACES

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2019 vol. 173 p. 549 - 556

0927-7765

Membrane structure is a key factor for the cell`s physiology, pathology,and therapy. Evaluating the importance of lipid species such as N-nervonoylsphingomyelin (24:1-SM) -able to prevent phase separation- to membrane structuring remains a formidablechallenge. This is the first report in which polarization-modulated infraredreflection-absorption spectroscopy (PM-IRRAS) is applied to investigate thelipid-lipid interactions in 16:0 vs 24:1-SM monolayers andtheir mixtures with 1,2-Dioleoyl-sn-glycero-3-phosphocholine (DOPC) and cholesterol(Chol) (DOPC/SM/Chol 2:1:1).  From the results we inferred thatthe cis double bond (Δ15) in 24:1-SM molecule diminishesintermolecular H-bonding and chain packing density compared to that of16:0-SM. In ternary mixtures containing 16:0-SM, the relative intensity ofthe two components of the Amide I band reflected changes in the H-bondingnetwork due to SM-Chol interactions. In contrast, the contribution of the maincomponents of the Amide I band in DOPC/24:1-SM/Chol remained as in 24:1-SMmonolayers, with a larger contribution of the non-H-bonded component. The mostinteresting feature in these ternary films is that the C=O stretching mode ofDOPC appeared with an intensity similar to that of SM Amide I band inDOPC/16:0-SM/Chol monolayers (a two-phase [Lo/Le] system),whereas an extremely low intensity of the C=O band was detected inDOPC/24:1-SM/Chol monolayers (single Le phase). This isevidence that the unsaturation in 24:1-SM affected not only theconformational properties of acyl chains but also the orientation of thechemical groups at the air/water interface.  The physical propertiesand overall H-bonding ability conferred by 24:1-SM may have implications in cellsignaling and binding of biomolecules.