Selectively conjugated melittins for liposome time-resolved fluoroimmunoassay of theophylline in serum

Theophylline (Th) has been selectively conjugated to the four amino groups of melittin (Mel) by solid phase peptide synthesis. The cytolytic activity of the resultant Th-Mel compounds was tested on liposomes trapping the bovine serum albumin (BSA) conjugate with 4,7-bis(chlorosulfophenyl)-1,10-phenanthrol ine-2,9-dicarboxylic acid (BCPDA). The loss of lytic activity was the highest for Th-K7-Mel. Th-G1-Mel retains almost the same lytic activity as Mel. A homogeneous liposome time-resolved fluoroimmunoassay (LITRFIA) of Th in serum has been carried out with Th-G1-Mel between 5 ng and 10 microg.