Alkyl- and aryl-substituted salicyl phosphates as detection reagents in enzyme-amplified fluorescence DNA...

Nine salicyl phosphate esters with hydrophobic substituents (5-phenyl, 5-(2,4-difluorophenyl), 5-tert-octyl, 5-cumyl, 5-(4-tert-butylphenyl, 5-(1-adamantyl), 5-(n-dodecyl), 5-(1,1-diphenylethyl, and 5-trityl) were synthesized and found to be good substrates for calf intestinal alkaline phosphatase. The enzymatic hydrolysis produced the corresponding salicylates, which were strongly fluorescent when excited by ultraviolet light around 300 nm with maximum emission at 420-435 nm. The salicylates were less soluble and/or more adhesive than the nonfluorescent salicyl phosphate substrates, resulting in localization of fluorescence signal, which is a requirement for membrane-based assays. The salicyl phosphates bearing 8-14 carbon substitutents were found to be suitable detection reagents for dot-blot DNA hybridization assays on nylon membrane using a biotinylated probe, allowing the detection of 125 pg of target pBR322 plasmid DNA using a simple apparatus consisting of a transilluminator, a camera. and a 455-nm cutoff optical filter.