peripheral protein

This term describes proteins that are loosely associated with a biological membrane, contrasting sharply with integral membrane proteins which penetrate the hydrophobic core of the lipid bilayer. Because they rely on electrostatic interactions or hydrogen bonding, these proteins can be dissociated from the membrane using relatively mild treatments, such as changes in pH or high salt concentrations.

In a laboratory or clinical context, the term is used to categorize proteins based on their localization and the method required to extract them. It is a technical term used almost exclusively in biochemistry, cell biology, and molecular medicine, and does not have a common metaphorical usage in general English.