Defining the statistical distribution of vesicle diameters facilitates quantitative assessment of spectral narrowing from small vesicles in protein/lipid interaction studies by 2H-NMR.
The diameters of vesicles comprising complexes of an integral membrane protein and 1,2-dimyristoyl-sn-glycero-3-phosphocholine, deuterated in the choline gamma-methyl groups, exhibited a lognormal distribution defined by the geometric mean (GM) and the logarithmic standard deviation (LSD). The range of vesicle sizes within each complex was very large (e.g., 99% of vesicles measured between 60 nm and 4,000 nm in one complex). This complicated assessment of spectral narrowing artefacts from small vesicles in broad line 2H-NMR results. Artefacts (e.g., decreases in quadrupole splitting and generation of two component spectra) resembled results attributed to membrane proteins in other 2H-NMR studies for which spectral narrowing was dismissed by demonstration of some vesicles > 400 nm in diameter. This was inadequate since 2H-NMR spectra from complexes with GM < 350 nm exhibited spectral narrowing artefacts despite the presence of some vesicles 1,200 nm in diameter. The nature and degree of artefact were determined by both GM and LSD. Quantifying vesicle sizes by GM and LSD accommodated the large size variation within a complex and facilitated quantitative assessment of artefacts through comparison of different complexes.
Department of Biochemistry, University of Oxford, U.K.
P
P
Gale
D001436:Bacteriorhodopsins / Q000737:chemistry* / Q000378:metabolism; D003903:Deuterium; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry* / Q000378:metabolism; D019617:Halobacterium salinarum / Q000378:metabolism; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008433:Mathematics; D008954:Models, Biological; D013816:Thermodynamics
D001436:Bacteriorhodopsins; D003903:Deuterium; D004134:Dimyristoylphosphatidylcholine