Synthesis of novel amphiphilic spin probes with the paramagnetic doxyl group in the polar region

The use of ESR and specially designed spin probes has led to major breakthroughs in understanding the complexity of biological membranes. Research has been focused mainly on molecular events within the lipid bilayer, and few probes have been designed for studying events in the extracellular space near the membrane surface. We have prepared a series of amphiphilic spin probes in which an ethylene glycol type hydrophilic spacer was introduced between a hydrophobic anchor and the doxyl group, placing the latter above the membrane in the extracellular space. Furthermore, the 2pπ orbital, containing the unpaired electron of the nitroxide group, would be orientated perpendicular to the membrane surface, making it more useful for ESR investigations of structural and dynamic properties close to the membrane surface in different situations of the cell life.