A ¹²⁵I-radiolabeled photoactivable reagent: iododiazofluorene for labeling membrane hydrophobic core

Abstract

2-Iododiazofluorene and 2,7-diiododiazofluorene have been developed as new reagents for labeling the membrane hydrophobic core. These compounds strongly absorb beyond 300 nm and rapidly insert into C-H bonds on photolysis in cyclohexane. 2-[¹²⁵I]Iododiazofluorene has been prepared and it easily partitions into egg phosphatidylcholine vesicles. Photolysis and product analysis indicated that 13.9% of the label inserted into the phosphatidylcholine. Further, the insertion was found to be exclusively associated with the fatty acyl chains and not the glycerophosphorylcholine part of phosphatidylcholine. The easy synthesis and purification procedure for 2-[¹²⁵I]iododiazofluorene and exclusive labeling of the hydrophobic core indicate that this reagent will be useful for studying artificial and natural membranes.