Protonated primary amines induced thymine quintets studied by electrospray ionization mass spectrometry and density functional theory calculations

Mass Spectrometry of Nucleic Acid Noncovalent Complexes

Nucleic acids have been among the first targets for antitumor drugs and antibiotics. With the unveiling of new biological roles in regulation of gene expression, specific DNA and RNA structures have become very attractive targets, especially when the corresponding proteins are undruggable. Biophysical assays to assess target structure as well as ligand binding stoichiometry, affinity, specificity, and binding modes are part of the drug development process. Mass spectrometry offers unique advantages as a biophysical method owing to its ability to distinguish each stoichiometry present in a mixture. In addition, advanced mass spectrometry approaches (reactive probing, fragmentation techniques, ion mobility spectrometry, ion spectroscopy) provide more detailed information on the complexes. Here, we review the fundamentals of mass spectrometry and all its particularities when studying noncovalent nucleic acid structures, and then review what has been learned thanks to mass spectrometry on nucleic acid structures, self-assemblies (e.g., duplexes or G-quadruplexes), and their complexes with ligands.

Isomer differentiation through supramolecular self-assembly in microdroplets of milliseconds life-time

Supramolecular recognition of thymine (or its analogs) with various central cations can form magic number clusters. Dual nano-ESI via theta tip emitters was used to on-line synthesize clusters. Even thermodynamically unstable clusters can be detected by MS thanks to the very short life-time (∼ms) of the generated microdroplets. By recording characteristic cluster distributions, isomers can be clearly differentiated in a novel "bottom-up" way. Theoretical calculations were performed to explain the MS results.

Heterogeneous cation induced clusters formed at surfaces of micro-droplets

A novel group of heterogeneous cations induced clusters (HeteroCICs) formed only at the surface of the micro-droplet is discovered by mass spectrometry (MS).

Highly sensitive and specific detection of histamine via the formation of a self-assembled magic number cluster with thymine by mass spectrometry

The self-assembled magic number cluster of thymine (T) significantly enhanced the MS signal of histamine with high specificity.