Solvation of propanediol ions by water molecules in the gas phase

Abstract

The thermochemical properties of protonated hydrates of 1,2-and 1,3-propanediols have been investigated using electrospray ionization-high pressure mass spectrometry. The binding enthalpies, entropies, and free energies of the stepwise hydration of protonated propanediols with one to three waters are reported. The observed negative entropy change [⌬⌬S 1,3 o for the addition of the third water to 1,3-propanediol⅐H ϩ (H 2 O) 2 suggests a stable structure due to an increased number of hydrogen bonds and the loss of the intramolecular hydrogen bond in the water cluster ion. The thermochemical properties of two isomers of butanediol were also investigated in order to further elucidate the structures of the protonated K nowledge of the thermochemical properties of non-covalent bonds, particularly those involving water and biologically significant molecules, is fundamental in understanding the molecular interactions and changes in protein conformations. The role of ionic clusters and the thermodynamics of cluster formation is of interest to many wide ranging areas of chemistry such as stratospheric chemistry and polar stratospheric clouds [1], the chemistry in the ionosphere [2], and the elucidation of enzymatic reaction mechanisms [3].A major advancement in methods to study solvated ions came with the development of electrospray mass spectrometry. This technique provided a solution to the difficulty of solvating doubly-charged ions [4] and provided information on the sites of protonation and proton affinities of gas-phase aromatic compounds [5]. Our laboratory has recently implemented this technique for the study of hydration of organic ions [6], thereby validating our experimental technique and method and providing new insights into the thermochemical properties of alkylammonium ions.Leikin and co-workers have reported differential effects of 1,2-and 1,3-propanediol on collagen selfassembly [7]. 1,2-propanediol was found to weakly inhibit fiber assembly and did not affect the interaction between collagen helices in fibers while, at the same concentration, 1,3-propanediol strongly suppressed fibrillogenesis and eliminated the attraction between collagen helices. The ability of these two diols to inhibit fiber assembly differs by more than an order of magnitude. Leikin proposed that hydrogen-bonded water clusters bridging opposing collagen fiber helices were disrupted by competition due to the formation of crucial hydrogen bonds with 1,3-propanediol. It was suggested that the efficiency to destabilize fibers is dependent on the ability of a species to compete with water for crucial hydrogen bonds and disrupt water bridges.In the present work, we sought to gain further insight into the interactions between water and the propanediols, and to contribute to a better understanding of fibrillogenesis inhibition. Reactions of protonated propanediols and water were studied using a variable temperature high pressure source mass spectrometer. Two protonated butanediols were also investigated to further characterize the effect o...

Nearest-neighbor parameters for the prediction of RNA duplex stability in diverse in vitro and cellular-like crowding conditions

“…As shown in Figure 2B , the lowest destabilization was observed in the 1,3-PDO solutions (green circles). This is due to the suitable positioning of the two hydroxyl groups in 1,3-PDO for the H-bonding interaction with water molecules ( 48 ), resulting in higher stabilities dominated by favorable enthalpy contributions as compared to the solution without any cosolute (Table S8). Interestingly, we observed the same correlation for cosolutes in both 1 M and 100 mM NaCl solutions, suggesting that Δ G ° 37, wa, dup is independent of the ionic concentration of the solution, thus validating the additive nature of Equation 7 .…”

12 Organic gas-phase ion chemistry

“…79 Laser ionization with TOF mass spectroscopy revealed magic numbers for stable clusters at (m,n) = (3,1), (4,2), (5,3), and (6,4) where m = number of dioxane molecules and n = number of water molecules involved in the cluster. Other gas-phase clustering reactions reported this year include the solvation of protonated propanediol ions by water molecules, 80 and the negative ion molecule reactions of C 2 H 5 NO 2 (O 2 ) 2 . 81 Operti, Rabezzana, Turco and Vaglio have investigated the generation of ion/ molecule clusters in propyne-ammonia and propyne-silane-ammonia systems, as well as in allene-phosphine and allene-silane-phosphine systems.…”