Patent ID: 7056653

Claim:
A method for determining binding of a species at a lipid-based surface having a local environment at a given pH or surface potential, wherein said binding is effective to alter said pH or potential, the method comprising: incorporating at said lipid-based surface a probe which comprises a pH- or potential-sensitive fluorophore attached to a steroid, to a head group of a sphingolipid or to a head group of a lipid having at least two chains, each chain comprising at least 14 carbon atoms in length, and wherein each independently said chain is selected from the group consisting of acyl, alkyl or alkenyl, wherein incorporation of the probe at the lipid-based surface is substantially not altered upon binding or dissociation of the species at the lipid-based surface and observing a change in a fluorescent property of said fluorophore retained at the surface upon binding or dissociation of said species at said lipid-based surface.