LIPOPHILIC PHOTOACTIVATABLE IODINATION PROBE
The lipophilic photoactivatable probe 125I-5-iodonaphthalene-1-azide(125I-INA), is now available in its radioactive form. 125I-INA is highly hydrophobic and readily partitions into biological membranes (partition coefficient:>105).
Upon irradiation with UV light (310 nm), 125I-INAwill selectively label membrane proteins which are either embedded or span the lipid bilayer. Labeling on membrane proteins by 125I-INA can be induced indirectly, by means of energy transfer using abundant fluorescent probes as photosensitizers. This feature allows the application of the photosensitized labeling technique (PSL), by which labeling of membrane proteins by 125I-INA can be targeted to discrete sites, or confined to specific sub-cellular compartments defined by fluorescent ligands or drugs.