Synthesis and properties of photoactivatable phospholipid derivatives designed to probe the membrane-associate domains of proteins

The total syntheses of photoactivatable phospholipidic probes 1 and 2 are described. These probes contain either an aryldiazonium function at their polar head (probes la and Ib) or an diazocyclohexadienonyl group attached to the end of one fatty acid side chain (probe 2) and have been designed to probe the lipid/water interface and the hydrophobic core of the membrane, respectively. The synthetic schemes include the possibility of incorporating a radio-labeled atom (tritium) for further labeling investigations. Both probes were stable in the dark under physiological conditions and could be efficiently photodecomposed at wavelengths above 300 nm, leading to the generation of highly reactive species, aryl cations and cyclohexadienonyl carbene, respectively. In addition, these probes displayed UV-absorption spectra which are compatible with tryptophan-mediated energy transfer photoactivation, which can lead potentially to an efficient mapping of the membrane-associate protein domains.