MAGNETIC ALIGNMENT OF BINARY MIXTURES OF PHOSPHOLIPIDS

点击翻译按钮获取中文摘要

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Binary mixtures of long and short chain phospholipids suspended in water spontaneously form flat disk-like lipid micelles, so-called bicelles. One of the most interesting properties of these bicelle suspensions is their ability to partially orient under the influence of an external magnetic field at temperatures above the main phase transition of the long chain lipid component. This mechanism can be used to macroscopically orient also proteins that are associated with these bicelles, although at present, the topology of the phase where magnetic alignment is observed is still disputed. This project was started to test the potential of this approach to study membrane protein interactions using small angle x-ray scattering taking advantage of this induced partial ordering in the system. So far we have successfully measured the disk form factor of the lipid bicelles for different ratios of long chain to short chain lipids. All mixtures measured exhibited macroscopic orientation at temperatures between 5¿C to 10¿C above the main phase transition of the long chain lipid when subjected to an external magnetic field of about 1 T. We also found that the addition of gramicidin, a small dimeric ion channel, to the lipid system does not significantly disturb the bicelle and we were able to achieve a similar quality of magnetic ordering in this peptide containing lipid system.