LANGMUIR MONOLAYER CHARACTERIZATION OF METAL CHELATING LIPIDS FOR PROTEIN TARGETING TO MEMBRANES

Targeting and organization of proteins on lipid membranes led to appli cations in both biological and materials sciences. Coordination of mem brane-bound metal ions by surface histidine residues provides a genera l method for targeting of proteins to membrane surfaces. Here we repor t the Langmuir monolayer properties of a new class of metal-chelating lipids. The lipids utilize the metal chelator iminodiacetate (IDA) as the hydrophilic headgroup, allowing display of divalent transition met al ions on the aqueous side of the membrane. Changes in surface pressu re-molecular area isotherms were used to observe metal binding, and an association constant for Cu2+ binding to the IDA lipids of 10(7-8) M- 1 was estimated. The ability to control binding site density is import ant for many applications. The IDA lipid was found to be miscible with both distearoylphosphocholine (DSPC) and 1-stearoyl-2-oleoyl-phosphoc holine (SOPC) at most compositions and surface pressures. (C) 1997 Els evier Science Ireland Ltd.