Lateral diffusion in sphingomyelin bilayers

Abstract

Sphingomyelin (SM) is an important lipid of eukaryotic cellular membranes and neuronal tissues. We studied lateral diffusion in macroscopically oriented bilayers of synthetic palmitoylsphingomyelin (PSM) and natural sphingomyelins of egg yolk (eSM), bovine brain (bSM) and bovine milk (mSM) by pulsed field gradient NMR (PFG NMR) in the temperature range 45-60 °C. We found that the mean values of lateral diffusion coefficients (LDCs) of SMs are 1.9-fold lower compared with those of dipalmitoylphosphatidylcholine (DPPC), which is similar in molecular structure. This discrepancy could be explained by the characteristics of intermolecular SM interactions. The LDCs of different SMs differ: egg SM is most similar to PSM; both of them have a 10% higher LDC value compared with the other two natural SMs. Besides, all natural SMs show a complicated form of the spin-echo diffusion decay (DD), which is an indicator of a distribution of LDC values in bilayers. This peculiarity is explained by the broad distributions of hydrocarbon chain lengths of the natural SMs studied here, especially mSM and bSM. We confirmed the relationship between chain length and LDC in the bilayers by computer analysis of a set of (1)H NMR spectra obtained by scanning the value of the pulsed field gradient. There is a correlation between lower LDC values and SM molecules with longer acyl chains. The most probable mechanisms by which long-chain SM molecules decrease their lateral diffusion relative to the average value are protrusion into the other side of the bilayer or lateral separation into areas that diverge with their LDCs.

Effect of Ca 2+ to Sphingomyelin Investigated by Sum Frequency Generation Vibrational Spectroscopy

“…These molecules act as mediators of signaling pathways that regulate cell growth, differentiation, multiple cell functions, cell apoptosis, and cellular calcium homeostasis (1)(2)(3). Sphingomyelins (SMs, N-acyl-sphingosine-1-phosphorylcholine) are the most common sphingolipids in eukaryotic cellular membranes and neuronal tissues (4). It has been reported that SM molecules along with cholesterol play a critical role in the formation of microdomains in biomembranes and lipid rafts (5)(6)(7).…”

“…Natural SMs usually contain a sphingosine backbone and an acyl chain of unequal length. The backbone possesses the 4,5-trans double bond, and the N-linked acyl chain is fully saturated and has a length of up to 30 carbon atoms (4,16).…”

Disordering of phospholipid headgroups induced by a small amount of polyethylene oxide

“…The degree of hydration, which reached around 23 wt%, was controlled by weighing the samples. The process of multi‐bilayer formation was checked by observing the sample in polarized light through the crossed polaroids and by observing 1 H NMR spectrum of the sample oriented at “magic angle.” It is known that the reproducibility in preparation of well‐oriented samples usually is not high, but our group has much of this experiences …”

“…A square sample tube containing macroscopically oriented lipid multi‐bilayers was placed in a specifically designed goniometer probe . A Chemagnetic InfinityPlus (Agilent, Fort Collins, CO) NMR spectrometer operating at proton frequencies of 360 MHz was used.…”

Interaction of polyacrylic acid with lipid bilayers: effect of polymer mass

“…There are at least two common ways to overcome spectral anisotropic broadening in lipid systems. One of them is to use macroscopically oriented lipid membranes, and the other is to use the well‐known solid‐state NMR MAS technique . The other is to use well known in solid state NMR MAS technique.…”