Amphipols Explained

Amphipols (a portmanteau of amphiphilic polymers) are a class of amphiphilic polymers designed to keep membrane proteins soluble in water without the need for detergents, which are traditionally used to this end but tend to be denaturing.^[1] Amphipols adsorb onto the hydrophobic transmembrane surface of membrane proteins thanks to their hydrophobic moieties and keep the complexes thus formed water-soluble thanks to the hydrophilic ones.^[2] Amphipol-trapped membrane proteins are, as a rule, much more stable than detergent-solubilized ones, which facilitates their study by most biochemical and biophysical approaches.^{[3] [4] [5]} Amphipols can be used to fold denatured membrane proteins to their native form^{[6] [7]} and have proven particularly precious in the field of single-particle electron cryo-microscopy (cryo-EM; see e.g. ^{[8] [9]}).The properties and uses of amphipols and other non-conventional surfactants are the subject of a book by Jean-Luc Popot.^[10]

See also

• Peptitergents - synthetic peptide sequences which can substitute to detergents to keep membrane proteins water-soluble.
• Nanodisc - water-soluble protein-stabilized lipid discs that can trap and stabilize membrane proteins.

Notes and References

1. Bowie. J. 2001. Stabilizing membrane proteins. Current Opinion in Structural Biology. 11. 4. 397–402. 10.1016/S0959-440X(00)00223-2. 11495729. 0959-440X.
2. Tribet. C. Audebert. R. Popot. JL. 24 December 1996. Amphipols: polymers that keep membrane proteins soluble in aqueous solutions.. Proceedings of the National Academy of Sciences of the United States of America. 93. 26. 15047–50. 1996PNAS...9315047T. 10.1073/pnas.93.26.15047. 26353. 8986761. free.
3. Popot, J.-L., et al. (2011) Amphipols from A to Z. Annu. Rev. Biophys. 40:379-408.
4. Zoonens, M., Popot, J.-L. (2014) Amphipols for each season. J. Membr. Biol. 247:759-796.
5. Popot, J.-L. (2018) Membrane proteins in aqueous solutions: From detergents to amphipols. Springer, New York, in the press.
6. Pocanschi, C.L., Dahmane, T., Gohon, Y., Rappaport, F., Apell, H.-J., Kleinschmidt, J.H., Popot, J.-L. (2006) Amphipathic polymers: tools to fold integral membrane proteins to their active form. Biochemistry 45:13954-13961.
7. Dahmane, T., Damian, M., Mary, S., Popot, J.-L., Banères, J.-L. (2009) Amphipol-assisted in vitro folding of G protein-coupled receptors. Biochemistry 48:6516-6521.
8. Althoff, T., Mills, D.J., Popot, J.-L., Kühlbrandt, W. (2011) Assembly of electron transport chain components in bovine mitochondrial supercomplex I1III2IV1. EMBO J. 30:4652-4664.
9. Liao, M., Cao, E., Julius, D., Cheng, Y. (2013) Structure of the TRPV1 ion channel determined by electron cryo-microscopy. Nature 504:107-112.
10. Popot, J.-L. (2018) Membrane proteins in aqueous solutions. From detergents to amphipols. Springer, New York, xxv + 708 p.