Showing papers on "Molecule published in 1998"
TL;DR: The architecture of the pore establishes the physical principles underlying selective K+ conduction, which promotes ion conduction by exploiting electrostatic repulsive forces to overcome attractive forces between K+ ions and the selectivity filter.
Abstract: The potassium channel from Streptomyces lividans is an integral membrane protein with sequence similarity to all known K+ channels, particularly in the pore region. X-ray analysis with data to 3.2 angstroms reveals that four identical subunits create an inverted teepee, or cone, cradling the selectivity filter of the pore in its outer end. The narrow selectivity filter is only 12 angstroms long, whereas the remainder of the pore is wider and lined with hydrophobic amino acids. A large water-filled cavity and helix dipoles are positioned so as to overcome electrostatic destabilization of an ion in the pore at the center of the bilayer. Main chain carbonyl oxygen atoms from the K+ channel signature sequence line the selectivity filter, which is held open by structural constraints to coordinate K+ ions but not smaller Na+ ions. The selectivity filter contains two K+ ions about 7.5 angstroms apart. This configuration promotes ion conduction by exploiting electrostatic repulsive forces to overcome attractive forces between K+ ions and the selectivity filter. The architecture of the pore establishes the physical principles underlying selective K+ conduction.
6,493 citations
TL;DR: In this article, the available data on gas phase basicities and proton affinities of approximately 1700 molecular, radical and atomic neutral species are evaluated and compiled, and tables of the data are sorted according to empirical formula and evaluated gas basicity.
Abstract: The available data on gas-phase basicities and proton affinities of approximately 1700 molecular, radical and atomic neutral species are evaluated and compiled. Tables of the data are sorted (1) according to empirical formula and (2) according to evaluated gas basicity. This publication constitutes an update of a similar evaluation published in 1984.
2,405 citations
TL;DR: Measurements of the interaction of the proteins Bcl-2 and Beclin, are shown to document the accuracy of this approach for correction of donor and acceptor concentrations, and cross talk between the different filter units.
886 citations
TL;DR: The protein-polysaccharide complexes exhibit better functional properties than that of the proteins and polysaccharides alone, and could be attributed to the simultaneous presence of the two biopolymers, as well as the structure of the complexes.
Abstract: Food proteins and polysaccharides are the two key structural entities in food materials. Generally, interactions between proteins and polysaccharides in aqueous media can lead to one- or two-phase systems, the latter being generally observed. In some cases of protein-polysaccharide net attraction, mainly mediated through electrostatic interactions, complex coac-ervation or associative phase separation occurs, giving rise to the formation of protein-polysac-charide complexes. Physicochemical factors such as pH, ionic strength, ratio of protein to polysaccharide, polysaccharide and protein charge, and molecular weight affect the formation and stability of such complexes. Additionally, the temperature and mechanical factors (pressure, shearing rate, and time) have an influence on phase separation and time stability of the system. The protein-polysacchaide complexes exhibit better functional properties than that of the proteins and polysaccharides alone. This improvement could be attributed to the simultaneou...
782 citations
TL;DR: In this paper, a donor-donor-acceptor−acceptor −acceptor (DDAA) array of hydrogen bonding sites in the 4[1H]-pyrimidinone tautomer was used to preorganize the molecules for dimerization.
Abstract: 6-Methyl-2-butylureidopyrimidone dimerizes via four hydrogen bonds in the solid state as well as in CHCl3 solution via a donor−donor−acceptor−acceptor (DDAA) array of hydrogen bonding sites in the 4[1H]-pyrimidinone tautomer. An intramolecular hydrogen bond from the pyrimidine NH group to the urea oxygen atom preorganizes the molecules for dimerization. The dimerization constant of the dimer in CHCl3 exceeds 106 M-1. In CHCl3 containing DMSO, the dimer is in equilibrium with the monomeric 6[1H]-pyrimidinone tautomer. In 6-phenyl-2-butylureidopyrimidone, the 4[1H]-pyrimidinone tautomer coexists with the pyrimidin-4-ol form, which dimerizes with similar high dimerization constants via four hydrogen bonds in a DADA array. The latter tautomer predominates in derivatives with electronegative 6-substituents, like 6-nitrophenyl- and 6-trifluoromethyl-2-butylureidopyrimidone. Due to its simple preparation and high dimerization constant, the ureidopyrimidone functionality is a useful building block for supramolecu...
673 citations
TL;DR: In this paper, the authors studied CO oxidation on Pt(111) with ab initio density functional theory and identified the low energy pathway and transition state for the reaction and the key event is the breaking of an O-metal bond prior to the formation of a chemisorbed ${\mathrm{CO}}_{2}$ molecule.
Abstract: CO oxidation on Pt(111) is studied with ab initio density functional theory The low energy pathway and transition state for the reaction are identified The key event is the breaking of an O-metal bond prior to the formation of a chemisorbed ${\mathrm{CO}}_{2}$ molecule The pathway can be rationalized in terms of competition of the O and C atoms for bonding with the underlying surface, and the predominant energetic barrier is the strength of the O-metal bond
659 citations
TL;DR: X-ray diffraction of bacteriorhodopsin crystals grown in cubic lipid phase revealed unexpected two-fold symmetries that indicate merohedral twinning along the crystallographic c axis.
Abstract: Photoisomerization of the retinal of bacteriorhodopsin initiates a cyclic reaction in which a proton is translocated across the membrane. Studies of this protein promise a better understanding of how ion pumps function. Together with a large amount of spectroscopic and mutational data, the atomic structure of bacteriorhodopsin, determined in the last decade at increasing resolutions, has suggested plausible but often contradictory mechanisms. X-ray diffraction of bacteriorhodopsin crystals grown in cubic lipid phase revealed unexpected two-fold symmetries that indicate merohedral twinning along the crystallographic c axis. The structure, refined to 2.3 angstroms taking this twinning into account, is different from earlier models, including that most recently reported. One of the carboxyl oxygen atoms of the proton acceptor Asp85 is connected to the proton donor, the retinal Schiff base, through a hydrogen-bonded water and forms a second hydrogen bond with another water. The other carboxyl oxygen atom of Asp85 accepts a hydrogen bond from Thr89. This structure forms the active site. The nearby Arg82 is the center of a network of numerous hydrogen-bonded residues and an ordered water molecule. This network defines the pathway of the proton from the buried Schiff base to the extracellular surface.
558 citations
TL;DR: The aΠu and bΠg States 2325 5.
Abstract: III. Formation of Carbon Clusters 2317 IV. Thermodynamic Properties 2319 V. C2 2319 A. Structure and Spectroscopy 2319 B. C2 2320 C. C2 2321 VI. C3 2321 A. Early Experimental Work 2321 B. Mid-IR and Far-IR Spectroscopy 2321 C. Electronic Spectroscopy 2323 1. The Σu + Ground State 2323 2. The AΠu State 2324 3. The Σu + State 2324 4. The aΠu and bΠg States 2325 5. Other Band Systems 2326 D. C3 in the Interstellar Medium 2326 E. C3 2326 F. C3 2327 VII. C4 2327 A. Theory 2327 B. Experiment 2328 1. The Rhombic Isomer 2328 2. The Linear Isomer 2328 C. Excited Electronic States 2330 D. C4 2331 E. C4 2332 VIII. C5 2332 A. Theory 2332 B. Experiment 2332 C. Excited Electronic States 2334 D. C5 2334 E. C5 2335 IX. C6 2335 A. Theory 2335 B. Experiment 2336 1. The Cyclic Isomer 2336 2. The Linear Isomer 2336 C. Excited Electronic States 2337 D. C6 2338 E. C6 2338 X. C7 2338 A. Theory 2338 B. Experiment 2338 C. Excited Electronic States 2340 D. C7 2340 E. C7 2340 XI. C8 2341 A. Theory 2341 B. Experiment 2342 1. The Cyclic Isomer 2342 2. The Linear Isomer 2342 C. Excited Electronic States 2342 D. C8 2342 E. C8 2342 XII. C9 2343 A. Theory 2343 B. Experiment 2343 C. Excited Electronic States 2345 D. C9 2345 E. C9 2345 XIII. C1
544 citations
TL;DR: The structural basis of the reaction of the hydroxyl radical with DNA is revealed, providing information on the mechanism of DNA damage caused by ionizing radiation as well as atomic-level detail for the interpretation of hydroxy radical footprints of DNA-protein complexes and chemical probe experiments on the structure of RNA and DNA in solution.
Abstract: Despite extensive study, there is little experimental information available as to which of the deoxyribose hydrogen atoms of duplex DNA reacts most with the hydroxyl radical. To investigate this question, we prepared a set of double-stranded DNA molecules in which deuterium had been incorporated specifically at each position in the deoxyribose of one of the four nucleotides. We then measured deuterium kinetic isotope effects on the rate of cleavage of DNA by the hydroxyl radical. These experiments demonstrate that the hydroxyl radical reacts with the various hydrogen atoms of the deoxyribose in the order 5′ H > 4′ H > 3′ H ≈ 2′ H ≈ 1′ H. This order of reactivity parallels the exposure to solvent of the deoxyribose hydrogens. Our work therefore reveals the structural basis of the reaction of the hydroxyl radical with DNA. These results also provide information on the mechanism of DNA damage caused by ionizing radiation as well as atomic-level detail for the interpretation of hydroxyl radical footprints of DNA-protein complexes and chemical probe experiments on the structure of RNA and DNA in solution.
497 citations
TL;DR: Within the past three years, a wide variety of molecules, ranging from OCS to large organic molecules such as amino acids and a number of van der Waals complexes and even large metal clusters, have been embedded in He droplets and studied either in infrared or in the visible region.
Abstract: ▪ Abstract Laser ablation of in situ metals has recently made it possible to immerse a large number of different metal atoms and ions and small clusters of metal atoms in liquid helium (He) and thus study their absorption and emission spectra in the visible region. Atoms and molecules are readily picked up by large ( ≥ 103 atoms) He droplets, and their spectra are sensitively detected through the use of either beam depletion following absorption or laser-induced fluorescence. Within the past three years, a wide variety of molecules, ranging from OCS to large organic molecules such as amino acids and a number of van der Waals complexes and even large metal clusters, have been embedded in He droplets and studied either in infrared or in the visible region. These results are discussed here in detail, and the evidence for the effect of superfluidity on the spectral features is reviewed.
486 citations
TL;DR: In this paper, a transition from ionic bonding to covalent bonding in a quantum-dot "artificial molecule" that is probed by microwave excitations was shown. But the transition was not considered in this paper.
Abstract: Quantum dots are small conductive regions in a semiconductor, containing a variable number of electrons (from one to a thousand) that occupy well-defined, discrete quantum states—for which reason they are often referred to as artificial atoms1. Connecting them to current and voltage contacts allows the discrete energy spectra to be probed by charge-transport measurements. Two quantum dots can be connected to form an ‘artificial molecule’. Depending on the strength of the inter-dot coupling (which supports quantum-mechanical tunnelling of electrons between the dots), the two dots can form ‘ionic’ (26) or ‘covalent’ bonds. In the former case, the electrons are localized on individual dots, while in the latter, the electrons are delocalized over both dots. The covalent binding leads to bonding and antibonding states, whose energy difference is proportional to the degree of tunnelling. Here we report a transition from ionic bonding to covalent bonding in a quantum-dot ‘artificial molecule’ that is probed by microwave excitations5,6,7,8. Our results demonstrate controllable quantum coherence in single-electron devices, an essential requirement for practical applications of quantum-dot circuitry.
TL;DR: The structure of an intact monoclonal antibody for phenobarbital, subclass IgG1, has been determined to 3.2 A resolution by X-ray crystallography, yielding a distorted Y shaped molecule.
TL;DR: Atomic force microscopy can be used to analyze the initial events in bacterial adhesion with unprecedented resolution and a method for determining whether bacteria are attracted or repelled by virtually any biomaterial of interest is developed.
Abstract: Bacterial adhesion and the subsequent formation of biofilm are major concerns in biotechnology and medicine. The initial step in bacterial adhesion is the interaction of cells with a surface, a process governed by long-range forces, primarily van der Waals and electrostatic interactions. The precise manner in which the force of interaction is affected by cell surface components and by the physiochemical properties of materials is not well understood. Here, we show that atomic force microscopy can be used to analyze the initial events in bacterial adhesion with unprecedented resolution. Interactions between the cantilever tip and confluent monolayers of isogenic strains of Escherichia coli mutants exhibiting subtle differences in cell surface composition were measured. It was shown that the adhesion force is affected by the length of core lipopolysaccharide molecules on the E. coli cell surface and by the production of the capsular polysaccharide, colanic acid. Furthermore, by modifying the atomic force microscope tip we developed a method for determining whether bacteria are attracted or repelled by virtually any biomaterial of interest. This information will be critical for the design of materials that are resistant to bacterial adhesion.
TL;DR: In this article, the synthesis of the solid form of C36 by the arc-discharge method was reported, and electron-diffraction patterns are consistent with a tightly bound molecular solid with an intermolecular spacing of 6.68
Abstract: Under appropriate non-equilibrium growth conditions, carbon atoms form relatively stable hollow clusters of well-defined mass number1, collectively known as fullerenes. The mass production, purification and condensation of such clusters into a molecular solid is generally essential to full experimental characterization: the initial discovery2 of C60, for example, had to await a bulk synthesis method3 six years later before detailed characterization of the molecule was possible. Gas-phase experiments1,4,5 have indicated the existence of a wide range of fullerene clusters, but beyond C60 only a few pure fullerene solids have been obtained6, most notably C70. Low-mass fullerenes are of particular interest because their high curvature and increased strain energy owing to adjacent pentagonal rings could lead to solids with unusual intermolecular bonding and electronic properties. Here we report the synthesis of the solid form of C36 by the arc-discharge method3. We have developed purification methods that separate C36 from amorphous carbon and other fullerenes, to yield saturated solutions, thin films and polycrystalline powders of the pure solid form. Solid-state NMR measurements suggest that the molecule has D6h symmetry, and electron-diffraction patterns are consistent with a tightly bound molecular solid with an intermolecular spacing of 6.68 A. We observe large increases in the electrical conductivity of the solid on doping with alkali metals.
TL;DR: Vibrational spectroscopies of small-sized hydrogen-bonded clusters of organic acids and related molecules, as well as their ions, are reviewed based on recent results.
Abstract: Vibrational spectroscopies of small-sized hydrogen-bonded clusters of organic acids and related molecules, as well as their ions, are reviewed based on our recent results. OH stretching vibrations of the jet-cooled clusters generated by supersonic expansions are observed by the various size-selected and population-labelling spectroscopic methods; ionization detected infrared (IR) and or stimulated Raman spectroscopies for the neutral clusters in the electronical ground state (S ) and fluorescence detected IR spectroscopy for the clusters in the electronically excited state (S ). The hydrogen-bond structures of phenol-(H O) clusters are n extensively investigated on the basis of the spectral analysis combined with ab initio calculations of their stable forms and vibrations. Remarkable enhancement of the hydrogen-bond strength upon electronic excitation is demonstrated for the IR spectra of the S clusters of phenol. For tropolone-(H O) and- (CH OH) n n clusters, (phenol), and fluorobenzene-(CH OH) clusters,...
TL;DR: Kinetic and enantioselectivity data provide unambiguous evidence for a mechanism involving cooperative, intramolecular bimetallic catalysis.
Abstract: Cooperative reactivity between multiple metal centers is commonly postulated for enzymatic systems1 and has evolved into an intriguing design principle for synthetic catalysts.2 We reported recently that the asymmetric ring opening (ARO) of meso epoxides with TMS-N3 catalyzed by (salen)Cr complex 13 displays a second-order kinetic dependence on catalyst.4 This observation led to a mechanistic proposal for the ARO involving simultaneous activation of epoxide and azide by two different catalyst molecules (Figure 1). We have undertaken the design of catalysts that enforce this cooperative mechanism through the construction of covalently linked dimeric complexes, and we describe here the synthesis and successful application of such systems as highly enantioselective and efficient ARO catalysts. Kinetic and enantioselectivity data provide unambiguous evidence for a mechanism involving cooperative, intramolecular bimetallic catalysis.
TL;DR: In this article, the optical modes in these structures have been studied spectroscopically as a function of the coupling and the mode energies are compared to detailed calculations, providing a rich picture of photonic modes.
Abstract: Photonic molecules have been fabricated by coupling pairs of micrometer-sized semiconductor cavities via a narrow channel. The optical modes in these structures have been studied spectroscopically as a function of the coupling and the mode energies are compared to detailed calculations. These results provide a rich picture of photonic modes in these molecules.
TL;DR: The application of small and weakly interacting probe molecules for the characterization of acidic and basic properties by FTIR spectroscopy is exemplified by using H- and alkali cation-exchanged zeolites as typical solid Bronsted and Lewis acids and Lewis bases as discussed by the authors.
Abstract: The application of small and weakly interacting probe molecules for the characterization of acidic and basic properties by FTIR spectroscopy is exemplified by using H- and alkali cation-exchanged zeolites as typical solid Bronsted and Lewis acids and Lewis bases. Criteria for the selection of probe molecules are given. Bronsted acidity can be characterized by the H-bonding method when CO and N2 are used as molecular probes. Quantum chemical calculations are shown to provide important additional information on the electronic nature of the adsorption interaction and the vibrational behaviour of the probe molecule. Lewis acidity dominates in cation-exchanged zeolites for small cations (Li+, Na+) whereas basic properties develop with increasing cation radius. CO, CO2, N2 and CH4 interact with cation centers, the interaction energy decreasing with increasing cation radius. CO at very low equilibrium pressures permits a siting of Na+, and the Al distribution in six-rings (SII-sites) can be probed. CH4 interacts with cations in the M+···H3CH configuration having C3v symmetry. CH-acids such as Cl3CH(D), acetylene and methylacetylene, are shown to be potentially suitable probe molecules for basic properties using the H-bonding method. All three molecules undergo Oz2−···H–C H-bonding and the induced red-shift of the C–H stretching frequency permits a ranking of the base strength of a given series of materials.
TL;DR: In this article, the relativistic regular approximation (ZORA) was used for the evaluation of the magnetic hyperfine interactions in paramagnetic molecules and the first order relations between the ZORA and Dirac formalism were given for the calculation of g-and A-tensors.
Abstract: Expressions are derived within the relativistic regular approximation (ZORA) for the evaluation of the magnetic hyperfine interactions in paramagnetic molecules. For hydrogen-like atoms exact first order relations between the ZORA and Dirac formalism are given for the calculation of g- and A-tensors. Density functional calculations are performed on the neutral atoms Cu, Ag and Au, on some small test molecules NO2, HCO, and TiF3, and on some paramagnetic clusters consisting of 5 or 7 atoms of the group IB metals: Cu7, Cu2Ag5, CuAg6, Ag5, Ag7, and Au7. It is shown that the calculated ESR parameters of the heptamers are in good agreement with results of experiments, which originally were assigned to pentamers.
TL;DR: In this paper, a donor-acceptor-donoracceptor array of four hydrogen-bonding sites is used to pre-organize the molecule for dimerization. But the structure of the compound is unknown.
Abstract: Highly stable dimers are formed in solution and in the solid state by a class of readily synthesized, self-complementary building blocks for supramolecular chemistry, which associate through a donor-acceptor-donor-acceptor array of four hydrogen-bonding sites. An additional intramolecular hydrogen bond in the compound whose crystal structure is shown on the right preorganizes the molecule for dimerization.
TL;DR: A large variety of new polyoxovanadates have been synthesized during the past few years by sol-gel chemistry or hydrothermal methods as discussed by the authors, which offer many advantages compared to the usual solid state syntheses.
TL;DR: In this paper, a 1:1:3 ratio in Me2CO was used to obtain [V4O2(O2CR)7(bpy)2](ClO4) (R = Et, 1; R = Ph, 4).
Abstract: Reactions of VCl3(THF)3, bpy, and NaO2CR (R = Et, Ph; bpy = 2,2‘-bipyridine) in a 1:1:3 ratio in Me2CO give [V4O2(O2CR)7(bpy)2](ClO4) (R = Et, 1; R = Ph, 4) following addition of NBun4ClO4. Use of 4,4‘-dimethyl- or 5,5‘-dimethylbipyridine (4,4‘-Me2bpy and 5,5‘-Me2bpy, respectively) and R = Et leads similarly to [V4O2(O2CEt)7(L−L)2](ClO4) (L−L = 4,4‘-Me2bpy, 2; L−L = 5,5‘-Me2bpy, 3). Yields are in the 38−90% range. The cation of 1 is isostructural with previously prepared [M4O2(O2CR)7(bpy)2]+ (M = CrIII, MnIII, FeIII) species and possesses a [V4O2] butterfly core. 1D and 2D COSY 1H NMR spectra of 1 show the solid-state structure is retained on dissolution. The effective magnetic moment (μeff) per V4 for 1 gradually rises from 5.79 μB at 300 K to a maximum of 6.80 μB at 25.0 K and then decreases rapidly to 4.72 μB at 2.00 K. The data in the 7.00−300 K range were fit to the appropriate theoretical expression (based on Ĥ = −2JSi·Sj) to give Jbb = −31.2 cm-1, Jwb = +27.5 cm-1, and g = 1.82, (b = body, w = wing...
TL;DR: In this paper, the generalized Born (GB) model is used to estimate free energies of A and B form structures of DNA obtained from molecular dynamics simulations, and the results provide an account of the conformational preferences of right-handed DNA in solution.
Abstract: The generalized Born (GB) model provides rapid estimates of the electrostatic free energies of solvation for diverse molecules and molecular ions. This method is expected to be of considerable utility for studies of solvation in macromolecular and biological systems. Calculations on biological molecules are typically based on empirical energy functions, each of which have their own prescriptions for determining net atomic charges. For maximum compatibility, GB parameters tailored to specific force fields are required. The development of parameters compatible with the AMBER force field is described. The method is used to estimate free energies of A and B form structures of DNA obtained from molecular dynamics simulations. The results provide an account of the conformational preferences of right-handed DNA in solution.
TL;DR: In this article, the process of thermal dissociation of trapped gas-phase ions by the ambient blackbody radiation field surrounding the ions was investigated and it was shown that the radiation can be used as a mechanism for activating unimolecular thermal dissociations of gas phase molecules.
Abstract: The historical “radiation hypothesis” as a mechanism for activating unimolecular thermal dissociation of gas-phase molecules, long discredited on the authority of Langmuir, has been revitalized by the discovery and characterization of the process of thermal dissociation of trapped gas-phase ions by the ambient blackbody radiation field surrounding the ions. This development was made possible by improvements in Fourier transform ion cyclotron instrumentation that allowed long-time trapping of weakly bound cluster ions at extremely low pressures. Binding energies can be derived from measurements of these dissociation rate constants both by detailed kinetic modeling and by simpler Arrhenius temperature-dependence approaches, although the latter require special considerations for small molecules. These approaches have been applied to thermal dissociations of molecules, including cluster ions and large biomolecule ions.
TL;DR: Nanometer-sized bowls: six metal centers and four tridentate ligands self-assemble in aqueous solution to give the macrotricycle 1, which has approximate dimensions of 3×2×2 nm.
Abstract: Nanometer-sized bowls: six metal centers and four tridentate ligands self-assemble in aqueous solution to give the macrotricycle 1, which has approximate dimensions of 3×2×2 nm Another macrocycle (not shown), obtained with a different ligand, is of similar size and topology but differs considerably from 1 in its host-guest behavior
TL;DR: The Freundlich isotherm equation, in the form of theta = KP1/n, was derived by treating the model with the ensemble theory in statistical mechanics as a theoretical tool, the model being set up for the adsorption system with emphasis on two factors, namely the lateral interaction between the Adsorbed molecules and the energetic surface heterogeneity.
TL;DR: In this article, the electronic properties of three-centered hydrogen bonds (HBs) were investigated by means of the atoms in molecules (AIM) approach, and the existence of bifurcated bond paths in the AIM analysis with electron densities was shown.
Abstract: The nature of bifurcated or three-centered hydrogen bonds (HB) has been investigated. Different families of compounds were chosen: monomers with intramolecular three-centered HB, dimers with a HB donor (HBD) and a molecule with two HB acceptor (HBA) groups, and trimers with one HBD and two HBAs. All the systems were optimized at the B3LYP/6-31G* level, and, in the case of the complexes, the interaction energies were evaluated and corrected with the basis set superposition error (BSSE). The electronic nature of these three-centered HBs was analyzed by means of the atoms in molecules (AIM) approach. The present study indicates the existence of bifurcated bond paths in the AIM analysis with electron densities that can be classified as follows: (i) compounds with symmetric three-centered HBs presenting two symmetric bond critical points with equal values of electron density; (ii) compounds with asymmetric three-centered HBs presenting two bond critical points with different values of electron density; (iii)...
TL;DR: There are additional sources of information that can complement NOEs in cases where positioning of remote parts of molecules is important, and where extension to larger and more complex systems is desired.
Abstract: Structure determination of biomolecules by NMR has traditionally been based on nuclear Overhauser effects (NOEs). Now there are additional sources of information that can complement NOEs in cases where positioning of remote parts of molecules is important, and where extension to larger and more complex systems is desired.
TL;DR: In this paper, the authors used the ab initio total energy method based on the gradient-corrected local density approximation to model the experimentally observed water monolayer on the MgO (100) surface and showed that the lateral interactions between the adsorbed water molecules, the formation of hydrogen bonds, and the resulting strong dimerization of the adsorbate promote the dissociation of two out of six water molecules in the surface unit cell.
Abstract: Using the ab initio total energy method based on the gradient-corrected local density approximation we have modeled the experimentally observed ( $3\ifmmode\times\else\texttimes\fi{}2$) water monolayer on the MgO (100) surface. The lateral interactions between the adsorbed water molecules, the formation of hydrogen bonds, and the resulting strong dimerization of the adsorbate promote the dissociation of two out of six water molecules in the surface unit cell. Although, on the theoretical grounds, water dissociation on a defective MgO surface has been already reported, this is the first theoretical evidence of water dissociation on the perfect MgO (100) surface.