Nanodisc

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Nanodisc

A nanodisc is a tiny, disc-shaped piece of lipid bilayer surrounded by stabilizing molecules. It provides a simple, native-like environment to study membrane proteins.

- Structure: A flat lipid bilayer, about 10 nanometers in diameter, encircled by amphipathic scaffolds—originally membrane scaffold proteins (MSPs) derived from apolipoprotein A1, or by peptides, or by synthetic polymers. The stabilizing belt holds the lipids together in a circular disk.

- MSP nanodiscs: In the classic design, MSPs wrap around the lipids in a double belt to form a discoidal nanoparticle. The size can be tuned by using MSPs of different lengths (for example, MSP1 vs MSP2). They resemble high-density lipoproteins (HDL) and faithfully mimic a membrane environment. Nanodiscs solubilize and stabilize membrane proteins, helping functional and structural studies, and are generally more native-like than detergents, micelles, or liposomes.

- Peptide nanodiscs: Instead of MSPs, amphipathic peptides form the stabilizing belt. These nanodiscs are similar in structure and can stabilize membrane proteins, but they often have higher size variability and can be less stable. Stability can be improved by peptide dimerization or polymerization.

- Synthetic/Native nanodiscs: Polymers such as styrene-maleic acid (SMA) copolymers form SMALPs, while diisobutylene-maleic acid (DIBMA) forms DIBMA nanodiscs. These polymers can extract membrane proteins directly from cells or from raw extracts and preserve native lipids. They are increasingly used to study lipid composition, protein-lipid interactions, and to obtain high-resolution structures by cryo-EM. They are also explored for drug delivery in some contexts.

- History: The first nanodiscs were created in 2002 by Bayburt, Grinkova, and Sligar using apoA1-derived MSPs. By varying MSP length, researchers can control the disc size. Over time, other approaches (peptide nanodiscs, SMA/DIBMA polymers) expanded the toolkit.

- Why use nanodiscs: They solubilize and stabilize membrane proteins in a near-native lipid environment, enabling accurate studies of structure and function without detergents that can destabilize proteins.