Can Nanodiscs be used to study membrane energetics?
Nanodiscs are very powerful technology for membrane protein invented in Stephen Sligar's lab at the University of Illinois.
A nanodisc is composed of a membrane protein, lipids and two monomers of a "scaffold protein". The most used scaffold protein is an N-terminal truncation of apolipoprotein A-1 (apoA-1), which is the primary protein component of high-density lipoprotein (HDL) particles. But because the size of the scaffold protein defines the size of the nanodisc, membrane proteins with different size could require different type of scaffold protein.

The reconstitution of a membrane protein into a lipid disc is a self assembled process. The reaction consists in mixing the membrane protein solubilised in detergent with lipids (that can be chosen according to the protein) and the scaffold protein. Removal of the detergent (using for example Bio-Beads™ SM-2 Resin) starts the self assembled process and the nanodiscs are created. 

Nanodiscs provide an environment where membrane proteins are stable and compatible with aqueous environments in a native-like phospholipid bilayer. The aquesous environment makes membrane proteins compatible with analytical methods that have primarily been limited to investigating soluble proteins. The lipidic environment, that can be chosen and optimised, keeps the membrane protein stable, monodisperse and active. The stoichiometry of the protein can also be controlled. 
Compared to nanodiscs, liposome are large, unstable and difficult to prepare with precisely controlled size and stoichiometry.

Several membrane proteins have now been reconstitued into nanodiscs and used for different type of studies, for example for studying ligand affinities  and kinetics, for NMR, for studying protein association state, signalling properties, and ion channels (http://molsense.com/applications/trubind-at-work/ion-channel-inhibitors/).

http://www.sciencedirect.com/science/article/pii/S0014579309007960