Zwitterions as protein repellents
01 Sep 2021



Researchers investigate how the length of the alkyll chain affects its reactions with water.

diagram showing the hydrogen bonds to water

​​​​​Water molecules strongly hydrate tethered sulfobetaine dizwitterions directed by electrostatic interactions and retain strong affinity for water even with a hexyl-groups separating the zwitterion. ​​


​Understanding the ability of a protein to stick to a surface is important in many industrial and biological applications. The ability to create a protein repellent surface and prevent biofouling is of great interest in areas such as marine coatings and design of diverse medical devices. One approach to enable this would be to create a surface system where the interactions with water are so favourable that proteins are excluded and not bound. 

One possible option is to use zwitterionic materials: molecules that contain both a positive and negative charge. This study, published in PCCP, studied dizwitterionic molecules, incorporating two zwitterionic sections at each end of an alkyl-chain spacer. The researchers investigated what happened to the water molecules surrounding the dizwitterionic molecule when the length of the alkyl-chain spacer was changed. 

They found that, for all chain lengths, each zwitterion end attracted a shell of about fifty water molecules. This high hydration activity suggests that this type of system may be suitable in applications where a protein-repellent is required.

Related publication: “Hydration of sulfobetaine dizwitterions as a function of alkyl spacer length.” Phys. Chem. Chem. Phys., 22, 16040-16050 (2020) 

DOI: 10.1039/D0CP02654A​

Contact: Jones, Evan (STFC,RAL,ISIS)