test: analysis of reaction products with RT-TLC and in vitro assay followed by LC-MS (Zeng and Zhan with modifications, reaction mixture consisting of 100 μM of FAD, 10 mM of NADH, 10 mM of KCl, 1.0 mM of substrates, 32 μM of prnF, 32 μM of DnHal in 100 μL of 0.1 M phosphate buffer (pH 7.0))