Resolving the two monolayers of a lipid bilayer in giant unilamellar vesicles using deuterium nuclear magnetic resonance. Biochemistry 1993 Sep 28;32(38):9936-43
Date
09/28/1993Pubmed ID
8399163DOI
10.1021/bi00089a009Scopus ID
2-s2.0-0027385040 (requires institutional sign-in at Scopus site) 17 CitationsAbstract
Giant unilamellar vesicles (GUVs) composed of mixtures of POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) plus DMPG (1,2-dimyristoyl-sn-glycero-3-phosphoglycerol) and/or CHOL (cholesterol) were prepared using detergent dialysis. Vesicles containing at least 30 mol % CHOL had diameters exceeding 450 nm. POPC in such GUVs, deuterium-labeled at either the choline alpha or beta segments, yielded deuterium (2H) and phosphorus (31P) nuclear magnetic resonance (NMR) Pake pattern line shapes, quadrupole splittings and chemical shift anisotropies identical to those obtained with multilamellar vesicles (MLVs) of identical composition. Exposing exclusively the vesicle exterior to either calcium or perchlorate ions, both of which are known to influence lipid head-group conformation through surface charge effects, caused the appearance of two overlapping 2H Pake patterns of equal intensity. The quadrupole splitting of one component remained unchanged while that of the second component was altered in the manner expected for choline alpha or beta deuterons in the presence of a cationic (calcium) or anionic (perchlorate) surface charge. Freeze-thawing the GUVs to equilibrate the exterior and interior vesicular contents eliminated the initially unchanged spectral component. It was likewise possible to resolve two quadrupole splittings when Staphylococcus aureus delta-toxin, a surface-active peptide known to influence lipid head-group orientational ordering, was added to the exterior vesicular solution only. This indicates that delta-toxin upon binding remains confined to one monolayer of the lipid bilayer and does not traverse the membrane.(ABSTRACT TRUNCATED AT 250 WORDS)
Author List
Marassi FM, Shivers RR, Macdonald PMAuthor
Francesca M. Marassi PhD Chair, Professor in the Biophysics department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
CholesterolDeuterium
Freeze Fracturing
Light
Lipid Bilayers
Magnetic Resonance Spectroscopy
Microscopy, Electron
Models, Biological
Phosphatidylcholines
Phosphatidylglycerols
Scattering, Radiation