ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTwo-dimensional heteronuclear NOE (HOESY) experiments: investigation of dipolar interactions between heteronuclei and nearby protonsChin Yu George C. LevyCite this: J. Am. Chem. Soc. 1984, 106, 22, 6533–6537Publication Date (Print):October 1, 1984Publication History Published online1 May 2002Published inissue 1 October 1984https://pubs.acs.org/doi/10.1021/ja00334a013https://doi.org/10.1021/ja00334a013research-articleACS PublicationsRequest reuse...

An important and exciting challenge in the postgenomic era is to understand functions of newly discovered proteins based on their structures. The main thrust find common structural motifs that contribute specific functions. Using this premise, here we report purification, solution NMR, functional characterization a novel class weak potassium channel toxins from venom scorpion <i>Heterometrus fulvipes</i>. These toxins, κ-hefutoxin1 κ-hefutoxin2, exhibit no homology any known toxins. NMR...

Chirality-switchable, 4-aminopyridine-based, pseudo-enantiomeric helicenes can catalyze enantiodivergent Steglich rearrangement in up to 91% ee (<italic>R</italic>) and 94% (<italic>S</italic>), respectively.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSolvent and intramolecular proton dipolar relaxation of the three phosphates ATP: a heteronuclear 2D NOE studyChin Yu George C. LevyCite this: J. Am. Chem. Soc. 1983, 105, 23, 6994–6996Publication Date (Print):November 1, 1983Publication History Published online1 May 2002Published inissue 1 November 1983https://pubs.acs.org/doi/10.1021/ja00361a059https://doi.org/10.1021/ja00361a059research-articleACS PublicationsRequest reuse permissionsArticle...

Allenoates and enones form cyclopentenes via a phosphine-catalyzed [3 + 2] cycloaddition while the amine-catalyzed [2 4] yields dihydropyrans or pyrans. The difference between these catalysts is studied with M06-2X/6-31+G* calculations. addition of catalyst to allenoate first step in both pathways followed by reaction enone. formation phosphorus-ylide exergonic, hence, kinetically favored over addition. Amines do not stabilize ammonium-ylides. However, electron-withdrawing groups on enone...

The ground state vinylidene–acetylene isomerization was investigated by ab initio molecular electronic structure theory. coupled-cluster method with single, double, and noniterative inclusion of triple excitations [CCSD(T)]; quadruple [CCSD(TQ)]; full (CCSDT) were used to treat the effect electron correlation. Several correlation-consistent polarized valence basis sets, cc-pVXZ, employed. Theoretical limiting values energetics reaction then deduced from series computations. With zero-point...

Effect(s) of organic solvents on an all β-sheet protein are investigated to understand the influence backbone conformation aggregation. Results obtained in present study reveal that aggregation is accompanied by formation non-native conformation. In contrast, induction helical segments found inhibit The differential effects secondary structures proposed stem from disparity nature hydrogen bonds and packing side chains hydrophobic residues α-helix our opinion, results provide useful hints...

Accurate three-dimensional quantum mechanical reaction probabilities are presented for the F+H2→HF+H on new global potential energy surface 5SEC total angular momentum J=0 over a range of translational energies from 0.15 to 4.6 kcal/mol. We find that v′=3 HF vibrational product state has threshold as low v′=2. also considerable structure in probability and cumulative curves which may be indicative resonance structures. compare these results those another 5SEC-W, differs magnitude van der...

The theoretical spectra of electroluminescent polymers are studied with time-dependent density functional theories, followed by a systematic scheme symmetry restriction to extrapolate the absorption and emission corresponding infinite chains avoiding periodic boundary conditions. Application poly(p-phenylene vinylene) (PPV) derivatives has been attempted, hybrid B3LYP is concluded be most suitable for computation. excitation energies PPV B3LYP/6-31G*//B3LYP/STO-3G B3LYP/6-311G* 2.107 2.027...

We present converged quantum dynamics calculations for the reaction F+H2(vi=0)→HF(vf=0,1,2,3)+H, where vi and vf denote initial final vibrational numbers, on potential-energy surface no. 5 of Muckerman.

Abstract Density functional theory has been used to calculate the thermodynamic properties and molecular orbitals of pillar[ n ]quinones. Pillar[ ]quinones are expected be effective electron acceptors ability accept more than one increases with size interior cavity. Pillar[5]quinone pillar[7]quinone show a great intramolecular charge transfer upon excitation from highest occupied orbital (HOMO) lowest unoccupied (LUMO) as indicated by large difference distributions between their HOMO LUMO...

The photoionization cross section can be expressed as a particular matrix element of the resolvent molecular electronic Hamiltonian. By using mixture real and complex Gaussian basis functions to form representation Hamiltonian it is possible use this expression compute sections from results diagonalization. This procedure based on variational principle for which calculated, applied in presence coupling between ionization channels. interference resonance features electron-ion scattering...

The cooperativity between hydrogen bonds and halogen in X–HCN–Y ( X: C 2 H , O, NH 3 HCI, HCN, HF; Y: HF, BrF, Br is analyzed with MP2/6-311++G(d, p) DFT/6-311++G(d, calculations using the B3LYP mPW1PW91 hybrid functionals. results from quantum chemical are typically clustered groups according to Y-ligand. By choosing X–HCN–HF group as reference it possible describe interaction bond a two-parameter model. value of first parameter model describes contribution X -ligand interbond cluster....

Several chemical properties of Lewis base-allenoate adducts (LB·allenoate), such as solvent effect, basicity, nucleophilicity and cycloaddition, are studied to provide a detailed foundation for the analysis LB-catalyzed reactions allenoates. The zwitterionic LB·allenoates formed between methyl allenoate bases, N-heterocyclic carbenes (NHCs), phosphines, amines aza-heterocycles, at M06-2X/6-31+G* level. addition LBs can yield Z- or E-type adducts. formation Z-type is more favorable in gas...

Sulfur trioxide (SO3) isolated in solid argon at 12 K was irradiated with light 193 nm from an ArF excimer laser. Recombination of photofragments O and SO2 produces OSOO that absorbs 1229.6, 1041.3, 597.6 cm−1. The assignments are based on observed 34S- 18O-isotopic shifts. Theoretical calculations using the B-P86 B3-LYP density functional methods were carried out for five isomers SO3; energies vibrational wave numbers predicted each one. Observed line positions, infrared intensities,...

We present a new formalism of the generalized Newton variational principle for calculation quantum mechanical state-to-state reaction probabilities. The reformulation involves solving directly transition matrix rather than reactance so that calculations may be carried out individual columns without obtaining solutions all possible initial channels. compare convergence with real and complex boundary conditions H+H2→H2+H, O+H2→OH+H, O+HD→OH+D OD+H.

Bergman cyclization of the enediynes (Z)-3-hexene-1,5-diyne (1), (Z)-3-heptene-1,5-diyne (2), (Z)-4-octene-2,6-diyne (3), (Z)-1-cyclononene-3,8-diyne (4), (Z)-1-cyclodecene-3,9-diyne (5), and (Z)-1-cycloundecene-3,10-diyne (6) has been studied by density functional methods. The reaction 1 was first using BP86, BLYP, BPW91, B3LYP functionals with 6-311G** basis set large ANO for latter two functionals. BPW91/6-311G** calculations yielded results comparing well those high-level ab initio...

Quantum calculations show that βO4′ links break in two ways; the carbanion route yields monomers, alkoxide facilitates repolymerisation.

[2,3]-Wittig rearrangements of sugar-derived dihydropyran allyl propargyl ethers located at the 2- or 4-position have been studied as useful means for extending carbon chains 4- 2-position with chirality transfer. The stereochemical course these reactions depends on following factors: (1) deprotonation pro-R pro-S-H, (2) equilibration lithiated stereogenic carbanion, (3) conformational inversion during rearrangement, and (4) concerted [2,3]- [1,2]-Wittig rearrangement. In some cases, a...

Abstract The conformation of oxytocin, the neurohypophyseal nonapeptide hormone, in solution deuterated dimethyl sulfoxide has been determined by 1 H‐nmr. structural determination is based on experimental data set nuclear Overhauser effect restraints. Obtained after restrained molecular dynamics simulation an initial structure extended conformation, five resultant structures satisfy restraints well. These resemble that crystal deamino‐oxytocin, analogue terms a close correlation observed...