Infrared Signature of Structures Associated with the H+(H2O)n (n = 6 to 27) Clusters.

Shin, Jae–Heon; Hammer, Nathan I.; Diken, Eric G.; Johnson, Mark A.; Walters, Richard; Jaeger, T. D.; Duncan, M. A.; Christie, Richard; Jordan, Kenneth D.

doi:10.1002/chin.200431007

Cited by 119 publications

(240 citation statements)

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“…In this paper, we contrast the behavior of the n = 20 hydrates of the H 3 O + and Cs + ions, both of which are preferentially generated in the M + (H 2 O) n cluster ion distributions (i.e., are magic numbers) and are thought to be based on a pentagonal dodecahedron motif (12 interconnected H-bonded pentagons). An important difference between these ions is that H 3 O + is predicted to reside on the surface of the cage (6,8,26), whereas Cs + is sequestered in its interior (27,28). We follow the evolution of the bands in the perdeuterated isotopologues, Cs + (D 2 O) 20 and D 3 O + (D 2 O) 20 , and find strong support for the earlier assignment of the spectral signature of the embedded H 3 O + ion.…”

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confidence: 54%

“…The intramolecular HOH bending and OH stretching modes of the surface water molecules are not strongly shifted by introduction of the ion, however, where the latter appear as a broad envelope spanning the 3,000-to 3,700-cm −1 range typical of liquid water. An interesting aspect of the D 2 tagged spectrum obtained with cryogenic cooling (as opposed to that reported on the same ion generated under the more rapid quenching conditions at play in a supersonic jet ion source) (8,11) is that distinct features begin to emerge above the continuous background absorption in the OH stretching region above 3,400 cm −1 .…”

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confidence: 87%

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Site-specific vibrational spectral signatures of water molecules in the magic H ₃ O ⁺ (H ₂ O) ₂₀ and Cs ⁺ (H ₂ O) ₂₀ clusters

Fournier

Wolke

Johnson

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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Theoretical models of proton hydration with tens of water molecules indicate that the excess proton is embedded on the surface of clathrate-like cage structures with one or two water molecules in the interior. The evidence for these structures has been indirect, however, because the experimental spectra in the critical H-bonding region of the OH stretching vibrations have been too diffuse to provide band patterns that distinguish between candidate structures predicted theoretically. Here we exploit the slow cooling afforded by cryogenic ion trapping, along with isotopic substitution, to quench water clusters attached to the H 3 O + and Cs + ions into structures that yield well-resolved vibrational bands over the entire 215-to 3,800-cm −1 range. The magic H 3 O + (H 2 O) 20 cluster yields particularly clear spectral signatures that can, with the aid of ab initio predictions, be traced to specific classes of network sites in the predicted pentagonal dodecahedron H-bonded cage with the hydronium ion residing on the surface.water clusters | cryogenic vibrational spectroscopy | hydrogen bonding O ver the last decade, the cooperative mechanics underlying the microhydration of simple ions has undergone a renaissance due to rapid advances in experimental and theoretical methods. On the experimental side, it is routine to capture and study size-selected species cooled to cryogenic temperatures (1-5), and theoretical techniques are now capable of handling tens of atoms with all-electron, "supermolecule" approaches, where complex hydration networks are treated in the ansatz of polyatomic molecular physics (6). A dramatic example of the new insights afforded by this combined approach is the recent elucidation of the spectral signature associated with the hydronium ion when it is accommodated on the surface of a pentagonal dodecahedral cage formed by the "magic" H 3 O + (H 2 O) 20 cluster (7). The theoretical structure proposed earlier (8) (denoted I) is illustrated in Fig. 1, and the recently reported D 2 predissociation spectrum of the cryogenically cooled, D 2 tagged H 3 O + (H 2 O) 20 cluster is compared with that observed for the H 3 O + (H 2 O) 3 Eigen cation (9, 10) in Fig. 1 A and B, respectively. The key bands derived from the OH stretching motions of the surface-embedded hydronium (denoted ν a H3O +) were assigned (7) to the broad features in the experimental spectrum about 500 cm −1 below the corresponding bands in the free Eigen cation. The intramolecular HOH bending and OH stretching modes of the surface water molecules are not strongly shifted by introduction of the ion, however, where the latter appear as a broad envelope spanning the 3,000-to 3,700-cm −1 range typical of liquid water. An interesting aspect of the D 2 tagged spectrum obtained with cryogenic cooling (as opposed to that reported on the same ion generated under the more rapid quenching conditions at play in a supersonic jet ion source) (8, 11) is that distinct features begin to emerge above the continuous background absorption in the OH stretchin...

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confidence: 54%

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confidence: 87%

Site-specific vibrational spectral signatures of water molecules in the magic H ₃ O ⁺ (H ₂ O) ₂₀ and Cs ⁺ (H ₂ O) ₂₀ clusters

Fournier

Wolke

Johnson

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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“…Experimentally, the IR spectra are being used to identify the geometrical structure of small clusters. [10,11,13,22,23] At the same time, theoretical IR spectra of water clusters are frequently simulated based on quantum-chemical computations to help determine the molecular structure of water clusters through comparing with experimental results. [5,6,[24][25][26] Regarding quantum-chemical studies of vibrations of larger clusters, the IR spectra of different (H 2 O) 20 isomers were calculated by Fanourgakis et al at the level of MP2 theory, where they demonstrated the different spectral features for the isomers and that these features could be related to the spectra of their constituent fragments.…”

Section: Introductionmentioning

confidence: 99%

Fingerprints in IR OH vibrational spectra of H2O clusters from different H-bond conformations by means of quantum-chemical computations

Liu

Ojamäe

2014

J Mol Model

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Abstract:The thermodynamic stabilities and IR spectra of the three water clusters (H 2 O) 20, (H 2 O) 54, and (H 2 O) 100 are studied by quantum-chemical computations. After full optimization of (H 2 O) 20,54,100 structures using the hybrid density functional B3LYP together with the 6-31+G(d, p) basis set, the electronic energies, zero-point energies, internal energies, enthalpies, entropies, and Gibbs free energies of the water clusters at 298 K are investigated. Furthermore, the OH stretching vibrational IR spectra of water molecules in (H 2 O) 20,54,100 are simulated and split into sub-spectra for different H-bond groups depending on the conformations of the hydrogen bonds. From the computed spectra the different spectroscopic fingerprint features of water molecules in different H-bond conformations in the water clusters are inferred.2

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“…Studies of water clusters have shed light not only on their fundamental properties (1)(2)(3)(4) but also on the mechanism employed by various nano-bio systems to fine-tune water and proton transport (5)(6)(7)(8)(9). A relevant example from biology is the M2 protein of the influenza A virus (10,11), which is the target of the influenza drugs amantadine and rimantadine (12)(13)(14)(15)(16)(17).…”

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confidence: 99%

Structure and mechanism of proton transport through the transmembrane tetrameric M2 protein bundle of the influenza A virus

Acharya

Carnevale

Fiorin

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

246

520

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The M2 proton channel from influenza A virus is an essential protein that mediates transport of protons across the viral envelope. This protein has a single transmembrane helix, which tetramerizes into the active channel. At the heart of the conduction mechanism is the exchange of protons between the His37 imidazole moieties of M2 and waters confined to the M2 bundle interior. Protons are conducted as the total charge of the four His37 side chains passes through 2 þ and 3 þ with a pK a near 6. A 1.65 Å resolution X-ray structure of the transmembrane protein (residues 25-46), crystallized at pH 6.5, reveals a pore that is lined by alternating layers of sidechains and well-ordered water clusters, which offer a pathway for proton conduction. The His37 residues form a box-like structure, bounded on either side by water clusters with wellordered oxygen atoms at close distance. The conformation of the protein, which is intermediate between structures previously solved at higher and lower pH, suggests a mechanism by which conformational changes might facilitate asymmetric diffusion through the channel in the presence of a proton gradient. Moreover, protons diffusing through the channel need not be localized to a single His37 imidazole, but instead may be delocalized over the entire His-box and associated water clusters. Thus, the new crystal structure provides a possible unification of the discrete site versus continuum conduction models.ion channels | M2 proton channel | membrane proteins | water clusters | histidine protonation W ater molecules confined at interfaces or in cavities behave differently from those in the bulk. Studies of water clusters have shed light not only on their fundamental properties (1-4) but also on the mechanism employed by various nano-bio systems to fine-tune water and proton transport (5-9). A relevant example from biology is the M2 protein of the influenza A virus (10, 11), which is the target of the influenza drugs amantadine and rimantadine (12-17). Tetrameric M2 (18) transports protons across the viral envelope to acidify the virion interior and trigger uncoating of the viral RNA prior to fusion of the viral envelope with the endosomal bilayer (19). M2 is one of the smallest bona fide channel/transporter proteins (96 residues), capable of pHdependent activation and highly selective conduction of protons vs. other ions (20)(21)(22)(23)(24)(25). A narrow pore leads to the highly conserved His37 and Trp41 residues (16,17,(26)(27)(28)(29), which are respectively responsible for proton selectivity (30) and asymmetry in the magnitude of conductance when the proton gradient is reversed (31). Thus the control of proton diffusion across the membrane relies on the ability of the imidazole moieties of His37 to accept and store protons from water molecules in the pore.An M2 peptide (residues 22-46), slightly longer than the transmembrane domain (32), associates into a functional four-helix bundle (33). Solid state 15 N nuclear magnetic resonance (ssNMR) experiments indicate that the first protons ...

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Infrared Signature of Structures Associated with the H⁺(H₂O)_n (n = 6 to 27) Clusters.

Cited by 119 publications

References 1 publication

Site-specific vibrational spectral signatures of water molecules in the magic H ₃ O ⁺ (H ₂ O) ₂₀ and Cs ⁺ (H ₂ O) ₂₀ clusters

Site-specific vibrational spectral signatures of water molecules in the magic H ₃ O ⁺ (H ₂ O) ₂₀ and Cs ⁺ (H ₂ O) ₂₀ clusters

Fingerprints in IR OH vibrational spectra of H2O clusters from different H-bond conformations by means of quantum-chemical computations

Structure and mechanism of proton transport through the transmembrane tetrameric M2 protein bundle of the influenza A virus

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Infrared Signature of Structures Associated with the H+(H2O)n (n = 6 to 27) Clusters.

Cited by 119 publications

References 1 publication

Site-specific vibrational spectral signatures of water molecules in the magic H 3 O + (H 2 O) 20 and Cs + (H 2 O) 20 clusters

Site-specific vibrational spectral signatures of water molecules in the magic H 3 O + (H 2 O) 20 and Cs + (H 2 O) 20 clusters

Fingerprints in IR OH vibrational spectra of H2O clusters from different H-bond conformations by means of quantum-chemical computations

Structure and mechanism of proton transport through the transmembrane tetrameric M2 protein bundle of the influenza A virus

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Infrared Signature of Structures Associated with the H⁺(H₂O)_n (n = 6 to 27) Clusters.

Site-specific vibrational spectral signatures of water molecules in the magic H ₃ O ⁺ (H ₂ O) ₂₀ and Cs ⁺ (H ₂ O) ₂₀ clusters

Site-specific vibrational spectral signatures of water molecules in the magic H ₃ O ⁺ (H ₂ O) ₂₀ and Cs ⁺ (H ₂ O) ₂₀ clusters