Quadruplex structures are higher order structures formed by guanine-rich oligonucleotides. In the present study, temperature-induced conformational changes in the quadruplex structures of aptamers and other guanine-rich oligonucleotides are probed by Raman spectroscopy. In particular, dramatic changes in the fingerprint region are observed in the spectra of thrombin binding aptamer at higher temperatures. These changes are accompanied by a decrease in the intensity of the 1480 cm−1 peak (attributed to C8 = N7-H2), which is diagnostic of the quadruplex structure. We also show that these changes can be reversed (to a certain extent) by addition of K+ ions
