DNA oligonucleotide ions forming G-quadruplex structures were studied in the gas phase using IRMPD spectroscopy. Data interpretation on these large biomolecule ions was made using carefully chosen control experiments. The major finding is a fingerprint of hydrogen bonding in the gas phase in the guanine C-6=O-6 stretching mode that allows probing of the conservation of G-quartets in the gas phase. The experiments demonstrate the conservation of G-quadruplex hydrogen bonds in the human telomeric sequence d(TTAGGG)(4).