Magnetically aligned membrane mimetics enabling comparable chiroptical and magnetic resonance spectroscopy studies

Abstract

Lipidic bicelles have been widely used for the analysis of integral membrane proteins where their spontaneous alignment in an magnetic field has been exploited for oriented sample solid-state NMR studies. Many of their physical properties however make them well suited to the analysis of membrane proteins by circular dichroism (CD) and synchrotron radiation circular dichroism (SRCD). In this paper we have identified bicelle compositions that permit comparable studies of integral membrane proteins by solid-state NMR, CD, and SRCD; complementary methods that can provide insights into protein structure and the interactions with drugs and other small molecules. Furthermore we have been able to identify bicelle compositions that allow the magnetic alignment of the bicelles at fields routinely available in magnetic CD instruments. This potentially provides a route to the preparation of samples for oriented CD that mitigates many of the issues associated with the preparation of mechanically aligned samples, although we demonstrate that the dynamics present within the system can complicate the analysis of such spectra.