An anomalous dissociation of protonated cluster ions of DNA guanine-cytosine base-pair

In the collisionally-activated dissociation of the proton-bound cluster ions of DNA base guanine (G) and cytosine (C), G••H+••C, the abundance of [CH+] ions was found to be higher than that of [GH+] despite the fact that G has a higher proton affinity than C. This unexpected observation seems to demonstrate another example that the simple kinetic method scheme does not work. We suggest that a kinetic factor or detailed dynamics governing the proton transfer and dissociation should be carefully considered in the applications of the kinetic method to the proton affinity measurements.