Anti-C4A monoclonal antibody, clone D5E304

Flavin-dependent monooxygenases must stabilize a C4a-hydroperoxyflavin intermediate to hydroxylate their respective substrates. Formation and decay of the C4a-hydroperoxyflavin were monitored under rapid reaction kinetic conditions in SidA, an N-hydroxylating monooxygenase involved in siderophore biosynthesis. Solvent kinetic isotope effect studies of flavin oxidation indicate that both hydrogen peroxide elimination and water elimination occur via abstraction of hydrogen from the N5 of the flavin. Kinetic isotope effect and density functional theory results are consistent with the transfer of a proton from the 2'-OH of the nicotinamide ribose of nicotinamide adenine dinucleotide phosphate (NADP(+)) to the C4a-peroxyflavin to form the C4a-hydroperoxyflavin. This represents a novel role for NADP(+) in the reaction of flavin-dependent enzymes.

Here, we report the first example of the utilization of p-nitro-tetradecyloxy-calix[4]arene (C4A-NO2) as a stationary phase for capillary gas chromatographic (GC) separations. The statically coated C4A-NO2 column exhibited a high column efficiency of 3815 plates per m and moderate polarity. The C4A-NO2 column was investigated for its separation performance and retention behaviours by utilizing a wide variety of isomer mixtures, covering alkylated benzenes and naphthalenes, alkenes, furans, alcohols, benzaldehydes, phenols and halogenated anilines. Importantly, the C4A-NO2 column exhibited high resolving capability for both aliphatic and aromatic isomers. Particularly, it displayed advantageous resolving capability over the commercial DB-17 column for halogenated aniline isomers. This work provides a good reference for designing calixarene derivatives as GC stationary phases, which is important for developing a family of stationary phases with specific selectivity.