Phase behavior and domain size in sphingomyelin-containing lipid bilayers

Robin S. Petruzielo; Frederick A. Heberle; Paul Drazba; John Katsaras; Gerald W. Feigenson

doi:10.1016/j.bbamem.2013.01.007

Phase behavior and domain size in sphingomyelin-containing lipid bilayers

Robin S. Petruzielo, Frederick A. Heberle, Paul Drazba, John Katsaras, Gerald W. Feigenson

Labs & Soft Matter

Research output: Contribution to journal › Article › peer-review

111 Scopus citations

Abstract

Membrane raft size measurements are crucial to understanding the stability and functionality of rafts in cells. The challenge of accurately measuring raft size is evidenced by the disparate reports of domain sizes, which range from nanometers to microns for the ternary model membrane system sphingomyelin (SM)/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/cholesterol (Chol). Using Förster resonance energy transfer (FRET) and differential scanning calorimetry (DSC), we established phase diagrams for porcine brain SM (bSM)/dioleoyl-sn-glycero-3-phosphocholine (DOPC)/Chol and bSM/POPC/Chol at 15 and 25 C. By combining two techniques with different spatial sensitivities, namely FRET and small-angle neutron scattering (SANS), we have significantly narrowed the uncertainty in domain size estimates for bSM/POPC/Chol mixtures. Compositional trends in FRET data revealed coexisting domains at 15 and 25 C for both mixtures, while SANS measurements detected no domain formation for bSM/POPC/Chol. Together these results indicate that liquid domains in bSM/POPC/Chol are between 2 and 7 nm in radius at 25 C: that is, domains must be on the order of the 2-6 nm Förster distance of the FRET probes, but smaller than the ~ 7 nm minimum cluster size detectable with SANS. However, for palmitoyl SM (PSM)/POPC/Chol at a similar composition, SANS detected coexisting liquid domains. This increase in domain size upon replacing the natural SM component (which consists of a mixture of chain lengths) with synthetic PSM, suggests a role for SM chain length in modulating raft size in vivo.

Original language	English
Pages (from-to)	1302-1313
Number of pages	12
Journal	Biochimica et Biophysica Acta - Biomembranes
Volume	1828
Issue number	4
DOIs	https://doi.org/10.1016/j.bbamem.2013.01.007
State	Published - Apr 2013

Funding

Support was received from The National Science Foundation Research Award MCB 0842839 and The National Institutes of Health R01 Research Award GM077198 (to G.W.F.), and from the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory (to J.K.), managed by UT-Batelle, LLC, for the U.S. Department of Energy (DOE). This work acknowledges the additional support from the DOE Office of Biological and Environmental Research, for the BioSANS instrument at the ORNL Center for Structural Molecular Biology, and from the Scientific User Facilities Division of the Office of Basic Energy Sciences, for the EQ-SANS instrument at the ORNL Spallation Neutron Source. These facilities are managed for DOE by UT-Battelle, LLC under contract no. DE-AC05-00OR2275. R.S.P. received support from the AT&T Labs Fellowship Program and a government support under and awarded by the Department of Defense, Air Force Office of Scientific Research, National Defense Science and Engineering Graduate (NDSEG) Fellowship , 32 CFR 168a .

Funders	Funder number
DOE Office of Biological and Environmental Research
Office of Basic Energy Sciences
UT-Batelle
National Science Foundation	MCB 0842839
National Institutes of Health
U.S. Department of Defense
U.S. Department of Energy
National Institute of General Medical Sciences	R01GM077198
Directorate for Biological Sciences	0842839
Air Force Office of Scientific Research
AT and T
Oak Ridge National Laboratory
National Defense Science and Engineering Graduate	32 CFR 168a

Keywords

Coexisting liquid phases
Lipid bilayer
Nanodomain
Raft
Small-angle neutron scattering
Sphingomyelin

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10.1016/j.bbamem.2013.01.007

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title = "Phase behavior and domain size in sphingomyelin-containing lipid bilayers",

abstract = "Membrane raft size measurements are crucial to understanding the stability and functionality of rafts in cells. The challenge of accurately measuring raft size is evidenced by the disparate reports of domain sizes, which range from nanometers to microns for the ternary model membrane system sphingomyelin (SM)/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/cholesterol (Chol). Using F{\"o}rster resonance energy transfer (FRET) and differential scanning calorimetry (DSC), we established phase diagrams for porcine brain SM (bSM)/dioleoyl-sn-glycero-3-phosphocholine (DOPC)/Chol and bSM/POPC/Chol at 15 and 25 C. By combining two techniques with different spatial sensitivities, namely FRET and small-angle neutron scattering (SANS), we have significantly narrowed the uncertainty in domain size estimates for bSM/POPC/Chol mixtures. Compositional trends in FRET data revealed coexisting domains at 15 and 25 C for both mixtures, while SANS measurements detected no domain formation for bSM/POPC/Chol. Together these results indicate that liquid domains in bSM/POPC/Chol are between 2 and 7 nm in radius at 25 C: that is, domains must be on the order of the 2-6 nm F{\"o}rster distance of the FRET probes, but smaller than the ~ 7 nm minimum cluster size detectable with SANS. However, for palmitoyl SM (PSM)/POPC/Chol at a similar composition, SANS detected coexisting liquid domains. This increase in domain size upon replacing the natural SM component (which consists of a mixture of chain lengths) with synthetic PSM, suggests a role for SM chain length in modulating raft size in vivo.",

keywords = "Coexisting liquid phases, Lipid bilayer, Nanodomain, Raft, Small-angle neutron scattering, Sphingomyelin",

author = "Petruzielo, {Robin S.} and Heberle, {Frederick A.} and Paul Drazba and John Katsaras and Feigenson, {Gerald W.}",

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T1 - Phase behavior and domain size in sphingomyelin-containing lipid bilayers

AU - Petruzielo, Robin S.

AU - Heberle, Frederick A.

AU - Drazba, Paul

AU - Katsaras, John

AU - Feigenson, Gerald W.

PY - 2013/4

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N2 - Membrane raft size measurements are crucial to understanding the stability and functionality of rafts in cells. The challenge of accurately measuring raft size is evidenced by the disparate reports of domain sizes, which range from nanometers to microns for the ternary model membrane system sphingomyelin (SM)/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/cholesterol (Chol). Using Förster resonance energy transfer (FRET) and differential scanning calorimetry (DSC), we established phase diagrams for porcine brain SM (bSM)/dioleoyl-sn-glycero-3-phosphocholine (DOPC)/Chol and bSM/POPC/Chol at 15 and 25 C. By combining two techniques with different spatial sensitivities, namely FRET and small-angle neutron scattering (SANS), we have significantly narrowed the uncertainty in domain size estimates for bSM/POPC/Chol mixtures. Compositional trends in FRET data revealed coexisting domains at 15 and 25 C for both mixtures, while SANS measurements detected no domain formation for bSM/POPC/Chol. Together these results indicate that liquid domains in bSM/POPC/Chol are between 2 and 7 nm in radius at 25 C: that is, domains must be on the order of the 2-6 nm Förster distance of the FRET probes, but smaller than the ~ 7 nm minimum cluster size detectable with SANS. However, for palmitoyl SM (PSM)/POPC/Chol at a similar composition, SANS detected coexisting liquid domains. This increase in domain size upon replacing the natural SM component (which consists of a mixture of chain lengths) with synthetic PSM, suggests a role for SM chain length in modulating raft size in vivo.

AB - Membrane raft size measurements are crucial to understanding the stability and functionality of rafts in cells. The challenge of accurately measuring raft size is evidenced by the disparate reports of domain sizes, which range from nanometers to microns for the ternary model membrane system sphingomyelin (SM)/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/cholesterol (Chol). Using Förster resonance energy transfer (FRET) and differential scanning calorimetry (DSC), we established phase diagrams for porcine brain SM (bSM)/dioleoyl-sn-glycero-3-phosphocholine (DOPC)/Chol and bSM/POPC/Chol at 15 and 25 C. By combining two techniques with different spatial sensitivities, namely FRET and small-angle neutron scattering (SANS), we have significantly narrowed the uncertainty in domain size estimates for bSM/POPC/Chol mixtures. Compositional trends in FRET data revealed coexisting domains at 15 and 25 C for both mixtures, while SANS measurements detected no domain formation for bSM/POPC/Chol. Together these results indicate that liquid domains in bSM/POPC/Chol are between 2 and 7 nm in radius at 25 C: that is, domains must be on the order of the 2-6 nm Förster distance of the FRET probes, but smaller than the ~ 7 nm minimum cluster size detectable with SANS. However, for palmitoyl SM (PSM)/POPC/Chol at a similar composition, SANS detected coexisting liquid domains. This increase in domain size upon replacing the natural SM component (which consists of a mixture of chain lengths) with synthetic PSM, suggests a role for SM chain length in modulating raft size in vivo.

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KW - Lipid bilayer

KW - Nanodomain

KW - Raft

KW - Small-angle neutron scattering

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SN - 0005-2736

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EP - 1313

JO - Biochimica et Biophysica Acta - Biomembranes

JF - Biochimica et Biophysica Acta - Biomembranes

IS - 4

ER -

Phase behavior and domain size in sphingomyelin-containing lipid bilayers

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