Probing the dependence of long-range, four-atom interactions on intermolecular orientation. 1. Molecular hydrogen and iodine monochloride

The dependence of the long-range interactions between molecular hydrogen and iodine monochloride on the geometry between the molecules is investigated. Laser-induced fluorescence and action spectroscopy experiments have identified multiple conformers of the o,p-H2...I35,37Cl(X,v' '=0) van der Waals complexes. A conformer with the hydrogen molecule localized at the iodine end of the dihalogen, most likely with C2v symmetry, is significantly more stable than an asymmetric conformer with the hydrogen localized in the well oriented orthogonally to the I-Cl bond axis, D0' ' = 186.4(3) cm-1 versus 82.8(3) 相似文献   

Pyrene‐Based Quantitative Detection of the 5‐Formylcytosine Loci Symmetry in the CpG Duplex Content during TET‐Dependent Demethylation

Methylcytosine (5mC) is mostly symmetrically distributed in CpG sites. Ten‐eleven‐translocation (TET) proteins are the key enzymes involved in active DNA demethylation through stepwise oxidation of 5mC. However, oxidation pathways of TET enzymes in the symmetrically methylated CpG context are still elusive. Employing the unique fluorescence properties of pyrene group, we designed and synthesized a sensitive fluorescence‐based probe not only to target 5‐formylcytosine (5fC) sites, but also to distinguish symmetric from asymmetric 5fC sites in the double stranded DNA context during TET‐dependent 5mC oxidation process. Using this novel probe, we revealed dominant levels of symmetric 5fC among total 5fC sites during in vitro TET‐dependent 5mC oxidation and novel mechanistic insights into the TET‐dependent 5mC oxidation in the mCpG context.     

Probing the dependence of long-range, four-atom interactions on intermolecular orientation: 2. Molecular deuterium and iodine monochloride

Laser-induced fluorescence and action spectroscopy experiments have identified multiple conformers of the D2...ICl van der Waals complex for both ortho-D2 (o-D2) and para-D2 (p-D2). As with the analogous H2...ICl van der Waals complexes [Darr, J. P.; Crowther, A. C.; Loomis, R. A.; Ray, S. E.; McCoy, A. B. J. Phys. Chem. A 2007, 111, 13387], the C2v conformer with the deuterium molecule localized at the iodine atom end of the dihalogen is significantly more stable than the asymmetric conformer that has the deuterium positioned orthogonally to the ICl bond axis, D0' = 223.9(2.4) versus 97.3(8)-103.9(3) cm(-1) for p-D2...I(35)Cl(X, v'=0). For both conformers, complexes containing p-D2 are found to be more strongly bound than those with o-D2. The electronically excited D2...ICl(A, v') and D2...ICl(B, v') complexes are found to have equilibrium geometries that are nearly the same as those of the ground-state asymmetric structures. Calculated D2...ICl(B, v'=3) energies and probability amplitudes obtained using a simple scaled He + ICl(B, v'=3) potential provide clues to the nature of the different excited-state levels accessed.     

Partitioning and adsorption in gas-liquid-solid chromatography: Models of temporal moments for retention and variance

Summary The resolution of gaseous chemical species in gasliquid-solid chromatography is influenced by absorption (partitioning) in the liquid and adsorption at the liquid-solid interface. We consider fundamental mass transfer models with adsorption and partitioning effects for solid chromatographic supports covered with thin films of stationary liquid. The dynamic models, based on mass-balance partial-differential equations, include the significant phenomena: convection, axial dispersion, gas-liquid mass transfer, intraparticle diffusion, and liquid-solid adsorption. Expressions for retention time and band variance (first and second temporal moments) are presented and evaluated for four distinct models: (1) capillary tube with inner surface covered with a uniform-thickness liquid film, (2) column of nonporous spheres covered with a uniform-thickness liquid film, (3) porous spherical particles with intraparticle pores covered with a uniform-thickness liquid film, (4) porous spherical particles with intraparticle pores completely filled with liquid.     

Ebselen and congeners inhibit NADPH oxidase 2-dependent superoxide generation by interrupting the binding of regulatory subunits

NADPH oxidases (Nox) are a primary source of reactive oxygen species (ROS), which function in normal physiology and, when overproduced, in pathophysiology. Recent studies using mice deficient in Nox2 identify this isoform as a novel target against Nox2-implicated inflammatory diseases. Nox2 activation depends on the binding of the proline-rich domain of its heterodimeric partner p22phox to p47phox. A high-throughput screen that monitored this interaction via fluorescence polarization identified ebselen and several of its analogs as inhibitors. Medicinal chemistry was performed to explore structure-activity relationships and to optimize potency. Ebselen and analogs potently inhibited Nox1 and Nox2 activity but were less effective against other isoforms. Ebselen also blocked translocation of p47phox to neutrophil membranes. Thus, ebselen and its analogs represent a class of compounds that inhibit ROS generation by interrupting the assembly of Nox2-activating regulatory subunits.     

Deuteration effects on the structure and infrared spectrum of CH5(+)

The CH5+ molecular ion is well-known for its large amplitude motions that lead to complete scrambling of the hydrogen atoms, even in the vibrational ground state. Experiments have been reported that probe the consequences of these large amplitude motions. We recently reported that quantum zero-point effects partially quench the scrambling when CH5+ is partially deuterated. Here, the consequences of this quantum localization are investigated through calculations of the low-resolution spectra of CH4D+, CHD4+, and CD5+. The spectra are obtained by convoluting stick spectra, evaluated for individual stationary points on an ab initio potential surface, multiplying them by Diffusion Monte Carlo ground state density at that stationary point, and taking the sum. The CH/D stretch regions of CH4D+ and CD5+ are red-shifted relative to CH5+, while the overall shape of the envelope remains unaffected. In contrast, for CHD4+, the shape of the spectral envelope in the CH/D stretch region differs from the other three isotopologs. These signatures of the quantum localization of the deuterium on the spectra are discussed.     

Polynomial identities,indices, and duality for theN=1 superconformal modelSM(2, 4v)

We prove polynomial identities for theN=1 superconformal modelSM(2, 4v) which generalize and extend the known Fermi/Bose character identities. Our proof uses theq-trinomial coefficients of Andrews and Baxter on the bosonic side and a recently introduced very general method of producing recursion relations forq-series on the fermionic side. We use these polynomials to demonstrate a dual relation underqq ^–1 betweenSM(2, 4v) andM(2v–1, 4v). We also introduce a genralization of the Witten index which is expressible in terms of the Rogers false theta functions.Dedicated to the memory of Claude Itzykson.     

Fundamental excitations of the shared proton in the H3O2- and H5O2+ complexes

We exploit recent advances in argon predissociation spectroscopy to record the spectroscopic signature of the shared proton oscillations in the H3O2- system and compare the resulting spectrum with that of the H5O2+ ion taken under similar conditions. Very intense 1 <-- 0 transitions are observed below 1100 cm(-1) in both cases and are surprisingly sharp, with the 697 cm(-1) transition in H3O2- being among the lowest in energy of any shared proton system measured to date. The assignments of the three fundamental transitions associated with the three-dimensional confinement of the shared proton in H3O2- are carried out with full-dimensional (DMC) calculations to treat this strongly anharmonic vibrational problem.