Quantification of arginine and its mono- and dimethylated analogs NMMA, ADMA and SDMA in biological fluids by LC–MS/MS: Is LC superfluous?

The use of plasmid DNA-based therapeutics relies on procedures that efficiently purify the supercoiled plasmid isoform. The present study describes a new strategy that uses a lysine ligand in affinity chromatography to efficiently separate supercoiled and open circular plasmid DNA isoforms. To achieve higher specificity in this chromatography it is essential to characterize the behaviour of binding/elution of supercoiled isoforms. The results show that the lysine support promotes complex interactions with supercoiled isoform, according to ionic strength and temperature manipulation.