The chemical structure of a G-quartet with metal ion coordination to O6 oxygen. The structure shows Hoogsteen hydrogen bonding motif between four guanine bases of a planar G-quartet. b) The structure of the intramolecular, parallel, propeller-type G-quadruplex formed by Myc2345 in the presence of K + . The K + lie between two G-quartets (which has not been shown here for better visualization of nucleotide folded structure). Yellow rectangles represent guanine bases in the C2-endo/anti conformation. c) Laser pulses used in EVV 2DIR experiments are shown schematically. The third probe beam (𝜔 𝛾 ), non-resonant in the electronic domain, is used to look at the polarisation produced by the two resonant IR beams, while the two infrared laser beams, 𝜔 𝛼 and 𝜔 𝛽 cause resonant vibrations of the system. The signal is anti-Stokes to probe beam photons, 𝜔 𝛿 = 𝜔 𝛾 + 𝜔 𝛽 -𝜔 𝛼 . d) Pulse sequence showing time delays between different pulses. The time delays used for all experimental measurements described in this work are 𝑇 𝛼𝛽 = 𝑇 𝛽𝛾 = 0.4 ps.