Bicelles Exhibiting Magnetically-Alignment for a broader range of temperatures - A Solid-State NMR Study.
Bicelles Exhibiting Magnetically-Alignment for a broader range of temperatures - A Solid-State NMR Study.
Langmuir. 2014 Jan 24;
Authors: Yamamoto K, Pearcy P, Ramamoorthy A
Abstract
Bicelles are increasingly used as model membranes to suitably mimic the biological cell membrane for biophysical and biochemical studies by a variety of techniques including NMR and X-ray crystallography. Recent NMR studies have successfully utilized bicelles for atomic-resolution structural and dynamic studies of antimicrobial peptides, amyloid peptides and membrane-bound proteins. Though bicelles composed with several different types of lipids and detergents have been reported, the NMR requirement of magnetic-alignment of bicelles limits the temperature range in which they can be used and subsequently their composition. Due to this restriction, low-temperature experiments desirable for heat-sensitive membrane proteins have not been conducted because bicelles could not be aligned. In this study, we characterize the magnetic-alignment of bicelles with various compositions for a broad range of temperatures using 31P static NMR spectroscopy in search of temperature-resistant bicelles. Our systematic investigation identified a temperature range of magnetic-alignment for bicelles composed of 4:1 DLPC:DHexPC, 4:1:0.2 DLPC:DHexPC:cholesterol, 4:1:0.13 DLPC:DHexPC:CTAB, 4:1:0.13:0.2 DLPC:DHexPC:CTAB:cholesterol, and 4:1:0.4 DLPC:DHexPC:cholesterol-3-sulfate. The amount of cholesterol-3-sulfate used was based on mole percent and was varied in order to determine the optimal amount. Our results indicate that the presence of 75 w% or more water is essential to achieve maximum magnetic-alignment, while the presence of cholesterol and cholesterol-3-sulfate stabilize the alignment at extreme temperatures and the positively charged CTAB avoids the mixing of bicelles. We believe that the use of magnetically-aligned 4:1:0.4 DLPC:DHexPC:cholesterol-3-sulfate bicelles at as low as -15 °C would pave avenues to study the structure, dynamics, and membrane orientation of heat-sensitive proteins such as cytochrome-P450 and could also be useful to investigate protein-protein interactions in a membrane environment.
PMID: 24460179 [PubMed - as supplied by publisher]
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