Influence of Chain Length and Unsaturation on Sphingomyelin Bilayers

Sphingomyelins (SMs) are among the most common phospholipid components of plasma membranes, usually constituting a mixture of several molecular species with various fatty acyl chain moieties. In this work, we utilize atomistic molecular dynamics simulations to study the differences in structural and...

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Bibliographic Details
Published in:Biophysical journal 2006-02, Vol.90 (3), p.851-863
Main Authors: Niemelä, Perttu S., Hyvönen, Marja T., Vattulainen, Ilpo
Format: Article
Language:English
Subjects:
1,2-Dipalmitoylphosphatidylcholine
Biophysical Theory and Modeling
Biophysics - methods
Carbon - chemistry
Computer Simulation
Diffusion
Electrons
Hydrogen Bonding
Lipid Bilayers - chemistry
Lipids
Membrane Fluidity
Membranes
Models, Chemical
Models, Molecular
Molecular Conformation
Phosphatidylcholines
Phospholipids - chemistry
Simulation
Sphingomyelins - chemistry
Sphingosine - chemistry
Studies
Time Factors
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Summary:Sphingomyelins (SMs) are among the most common phospholipid components of plasma membranes, usually constituting a mixture of several molecular species with various fatty acyl chain moieties. In this work, we utilize atomistic molecular dynamics simulations to study the differences in structural and dynamical properties of bilayers comprised of the most common natural SM species. Keeping the sphingosine moiety unchanged, we vary the amide bonded acyl chain from 16 to 24 carbons in length and examine the effect of unsaturation by comparing lipids with saturated and monounsaturated chains. As for structural properties, we find a slight decrease in average area per lipid and a clear linear increase in bilayer thickness with increasing acyl chain length both in saturated and unsaturated systems. Increasing the acyl chain length is found to further the interdigitation across the bilayer center. This is related to the dynamics of SM molecules, as the lateral diffusion rates decrease slightly for an increasing acyl chain length. Interdigitation also plays a role in interleaflet friction, which is stronger for unsaturated chains. The effect of the cis double bond is most significant on the local order parameters and rotation rates of the chains, though unsaturation shows global effects on overall lipid packing and dynamics as well. Regarding hydrogen bonding or properties related to the lipid/water interface region, no significant effects were observed due to varying chain length or unsaturation. The significance of the findings presented is discussed.
ISSN:0006-3495
1542-0086
DOI:10.1529/biophysj.105.067371