Gas-Phase Hydration Thermochemistry of Sodiated and Potassiated Nucleic Acid Bases

Abstract

Hydration reactions of sodiated and potassiated nucleic acid bases (uracil, thymine, cytosine, and adenine) produced by electrospray have been studied in a gas phase using the pulsed ion-beam high-pressure mass spectrometer. The thermochemical properties, ΔHon, ΔSon, and ΔGon, for the hydrated systems were obtained from hydration equilibrium measurement. The structural aspects of the hydrated complexes are discussed in conjunction with available literature data. The correlation between water binding energies in the hydrated complexes and the corresponding metal ion affinities of nucleobases suggests that a significant (if not dominant) amount of the canonical structure of cytosine undergoes tautomerization during electrospray ionization, and the thermochemical values for cationized cytosine probably correspond to a mixture of tautomeric complexes.

Ultraviolet photodissociation spectroscopy of cold, isolated adenine complexes with a potassium cation

“…This higher barrier for K + A9a(H 2 O) 3 can be explained by the strong interaction between K + ion and water molecules, previously observed in hydrated M + A complexes [10,19]. In K + A9a(H 2 O) 3 , K + ion forms Table 2 Partial atomic charges of the H atom in N9H and the N9 H bond lengths for A9, K + A9a, and K + A9b in the gas phase.…”

“…To understand these effects of alkali metal cations on DNA, metal ion-nucleobase complexes have been extensively studied as a simplified model system in recent decades [6][7][8][9][10][11][12]. The binding energies and metalation sites of M + (M = Li, Na, and K) to nucleobases were theoretically predicted [4,13,14].…”

Microhydration of Deprotonated Nucleobases

“…Water is the natural medium of biological systems, and for that reason our investigations are focused on the hydration of different ionic forms of nucleobases. In our previous studies, we investigated the thermochemical properties for the gas-phase hydration of protonated nucleobases and protonated nucleosides [ 45 ], sodiated and potassiated nucleobases [ 46 ], and protonated and sodiated thiouracils [ 47 ].…”

Gas phase hydration of polyethylene glycol–metal cation complexes

“…The knowledge of interactions between water molecules with metal‐cation‐organic molecule complexes (the complex hydration) provides information on the chemical properties of the complexes. Therefore, such interactions in the gas phase have been widely studied for a number of the complexes, eg, for complexes of amino acids, nucleobases, or crown ethers . Complexes of polyethylene glycols (PEGs, linear analogs of crown ether) and related compounds with metal cations have been already widely studied .…”