Zwitterionic sulfobetaine lipids that form vesicles with salt-dependent thermotropic properties.

We describe a class of zwitterionic sulfobetaine (SB) lipids with fascinating salt-dependent properties. SB lipids are zwitter-neutral across a broad pH range; however they have negative surface potentials in the presence of anions and two salt-dependent transition temperatures. These new SB lipids provide insight on the role of charge orientation at the membrane interface and may be useful components in drug delivery systems.