Exploring polar headgroup interactions between sphingomyelin and ceramide with infrared spectroscopy

Abstract

Ceramide is a major actor in the sphingolipid signaling pathway elicited by various kinds of cell stress. Under those conditions ceramide (Cer) is produced in the plasma membrane as a product of sphingomyelin (SM) hydrolysis, and this may lead to apoptosis. Thus, SM and Cer coexist in the membrane for some time, and they are known to separate laterally from the (more abundant) glycerolipids, giving rise to highly rigid domains or platforms. The properties of these domains/platforms are rather well understood, but the underlying SM:Cer molecular interactions have not been explored in detail. Infrared (IR) spectroscopy is a powerful analytical technique that provides information on all the chemical groupings in a molecule, and that can be applied to membranes and lipid bilayers in aqueous media. IR spectra can be conveniently retrieved as a function of temperature, thus revealing the thermotropic transitions of SM and its mixtures with Cer. Four regions of the IR spectrum of these sphingolipids have been examined, two of them dominated by the hydrophobic regions in the molecules, namely the C–H stretching vibrations (2800–3000 cm−1), and the CH2 scissoring vibrations (1455–1485 cm−1), and two others arising from chemical groups at the lipid-water interface, the sphingolipid amide I band (1600–1680 cm−1), and the phosphate vibrations in the 1000–1110 cm−1 region. The latter two regions have been rarely studied in the past. The IR data from the hydrophobic components show a gel (or ripple)-fluid transition of SM at 40 °C, that is shifted up to about 70 °C when Cer is added to the bilayers, in agreement with previous studies using a variety of techniques. IR information concerning the polar parts is more interesting. The amide I (carbonyl) band of pure SM exhibits a maximum at 1638 cm−1 at room temperature, and its position is shifted by about 10 cm−1 in the presence of Cer. Cer causes also a change in the overall band shape, but no signs of band splitting are seen, suggesting that SM and Cer carbonyl groups are interacting tightly, presumably through H-bonds. The 1086 cm−1 band, corresponding to PO2− vibrations, appears more stable in SM than in DPPC, and it is further stabilized by Cer, again suggesting an important role of H-bonds in the formation of SM:Cer clusters. Thus, SM and Cer can interact through their polar headgroups, in a way that is not accessible to other lipid classes.

Effects of aluminum chloride and coenzyme Q10 on the molecular structure of lipids and the morphology of the brain hippocampus cells

“…35 The range of 3020-2840 cm À1 represents the lipids' characterization and contains the CH bands. [36][37][38][39][40][41] The normalized absorbances (Norm. Abs.)…”

Glucosylceramide Associated with Gaucher Disease Forms Amyloid-like Twisted Ribbon Fibrils That Induce α-Synuclein Aggregation

“… 48 FTIR analysis revealed that the monomeric GlcCer exhibited two sharp peaks at 2850 and 2919 cm –1 , indicating characteristic symmetric and asymmetric stretching vibration of the ceramide CH 2 groups ( Figure 4 a). 48 Two other peaks, centered at 1632 and 1541 cm –1 , were observed, which correspond to the amide I and amide II groups. Further, two additional peaks were observed at 3289 and 3412 cm –1 , indicating amide A and hydroxyl groups of the polar sugar unit of GlcCer ( Figure 4 a).…”

“…46,47 To get additional structural insights and fit a twisted-ribbon model, we utilized TEM, AFM, Fourier-transform infrared (FTIR), powder X-ray diffraction (PXRD), and small-and wide-angle X-ray scattering (SAXS and WAXS) analyses. FTIR spectroscopy provides information on all functional groups present in a molecule 48,49 and has been extensively used to understand the molecular interaction between lipids, including sphingolipids, within bilayers in aqueous media. 48 FTIR analysis revealed that the monomeric GlcCer exhibited two sharp peaks at 2850 and 2919 cm −1 , indicating characteristic symmetric and asymmetric stretching vibration of the ceramide CH 2 groups (Figure 4a).…”

“…FTIR spectroscopy provides information on all functional groups present in a molecule , and has been extensively used to understand the molecular interaction between lipids, including sphingolipids, within bilayers in aqueous media . FTIR analysis revealed that the monomeric GlcCer exhibited two sharp peaks at 2850 and 2919 cm –1 , indicating characteristic symmetric and asymmetric stretching vibration of the ceramide CH 2 groups (Figure a) . Two other peaks, centered at 1632 and 1541 cm –1 , were observed, which correspond to the amide I and amide II groups.…”

Contribution of specific ceramides to obesity-associated metabolic diseases

“…Thereby, ceramides can assemble into raft-like ceramide-enriched membrane platforms (CEPs) to direct the recruitment, clustering, and activity of adaptors, receptors, and other signaling molecules [ 63 ]. Ceramides can also undergo polar headgroup interactions with other sphingolipid species [ 64 ]. A delicate balance of phase formation and transformation with mutual displacement of cholesterol by ceramides through interaction with sphingomyelin may exist, illustrating the interrelation of membrane sphingolipids and cholesterol and the multifaceted consequences resulting from imbalanced membrane ceramide plasticity [ 65 , 66 ].…”