Ion mobility spectrometry reveals intermediate states in temperature-resolved DNA unfolding

Electrospray ionization (ESI) mass spectrometry (MS) is used to study the non-covalent interactions of short 12-mer oligonucleotides under native conditions. A home-built, temperature-controlled ESI source is employed to elevate the spray temperature above the melting temperature (T-m) of the DNA duplexes, enabling the study of DNA interactions in the liquid phase rather than gas phase. Ion mobility spectrometry (IMS)-MS is used to investigate the 3-dimensional structure of the hybridized oligonucleotides and to track conformational changes in the oligonucleotide duplexes during temperature-induced melting in solution. Results show two additional drift times at T > 35 degrees C, indicating 2-fold (partial) unfolding dynamics for the DNA duplex with stable intermediates. (C) 2017 Elsevier B.V. All rights reserved.