The hydrogen molecule H2\rm{H}_{2} in inclined configuration in a weak magnetic field

Highly accurate variational calculations, based on a few-parameter, physically adequate trial function, are carried out for the hydrogen molecule \hh in inclined configuration, where the molecular axis forms an angle $\theta$ with respect to the direction of a uniform constant magnetic field ${\bf B}$, for $B=0,\, 0.1,\, 0.175$ and $0.2\,$a.u. Three inclinations $\theta=0^\circ,\,45^\circ,\,90^\circ$ are studied in detail with emphasis to the ground state $1_g$. Diamagnetic and paramagnetic susceptibilities are calculated (for $\theta=45^\circ$ for the first time), they are in agreement with the experimental data and with other calculations. For $B=0,\, 0.1$ and $0.2\,$a.u. potential energy curves $E$ vs $R$ are built for each inclination, they are interpolated by simple, two-point Pad\'e approximant $Pade[2/6](R)$ with accuracy of not less than 4 significant digits. Spectra of rovibrational states are calculated for the first time. It was found that the optimal configuration of the ground state for $B \leq B_{cr}=0.178\,$a.u. corresponds always to the parallel configuration, $\theta=0$, thus, it is a $^1\Sigma_g$ state. The state $1_g$ remains bound for any magnetic field, becoming metastable for $B > B_{cr}$, while for $B_{cr} < B < 12$\,a.u. the ground state corresponds to two isolated hydrogen atoms with parallel spins.Comment: 31 pages, 11 Tables, 7 Figures (2 new), following referee's suggestions parts 4,5,6 essentially rewritten, to be published at Journal of Quantitative Spectroscopy and Radiative Transfe

ExoMol molecular line lists – XX. A comprehensive line list for H3+

H3+ is a ubiquitous and important astronomical species whose spectrum has been observed in the interstellar medium, planets and tentatively in the remnants of supernova SN1897a. Its role as a cooler is important for gas giant planets and exoplanets, and possibly the early Universe. All this makes the spectral properties, cooling function and partition function of H3+ key parameters for astronomical models and analysis. A new high-accuracy, very extensive line list for H3+ called MiZATeP was computed as part of the ExoMol project alongside a temperature-dependent cooling function and partition function as well as lifetimes for excited states. These data are made available in electronic form as supplementary data to this article and at www.exomol.com

Benchmark Rovibrational Linelists and Einstein A-coefficients for the Primordial Molecules and Isotopologues

Complete benchmark rovibrational energy linelists calculated for the primordial polar molecules of the universe, namely HD+, HD, and the HeH+ isotopologues, with accuracy up to 10(-2) cm(-1) for low-lying states, are presented. To allow for these calculations to be performed, new high-accuracy potential energy curves, which include the diagonal Born-Oppenheimer adiabatic corrections and the leading relativistic corrections, are determined. Also, a new approach for calculating non-adiabatic corrections involving an effective vibrational nuclear mass obtained based on the atoms-in-molecules theory is employed. The vibrational and rotational masses are taken as being different and dependent on the nuclear distance. Accurate dipole moment curves are calculated and used to generate lists of Einstein A-coefficients. The energy linelists and the sets of Einstein A-coefficients for HD are upgrades of previous calculations including quasibound states, while for HD+ and HeH+ and its isotopologues the present results represent significant improvement over the previous calculations. The results obtained here suggest that, with the inclusion of the non-adiabatic corrections, the accuracy limit at least for low-lying states might have been reached. Thus, further progress should involve accounting for even smaller effects such as the quantum-electrodynamics corrections. The present results represent the state-of-the-art of theoretical spectroscopy of the primordial polar molecules.CAPES; Polish National Science Centre [DEC-2013/10/E/ST4/00033]; CNPqThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Topological Phases near a Triple Degeneracy

We study the pattern of three state topological phases that appear in systems with real Hamiltonians and wave functions. We give a simple geometric construction for representing these phases. We then apply our results to understand previous work on three state phases. We point out that the ``mirror symmetry'' of wave functions noticed in microwave experiments can be simply understood in our framework.Comment: 4 pages, 1 figure, to appear in Phys. Rev. Let

Fine Tuning: Effects of Post-Translational Modification on Hsp70 Chaperones

The discovery of heat shock proteins shaped our view of protein folding in the cell. Since their initial discovery, chaperone proteins were identified in all domains of life, demonstrating their vital and conserved functional roles in protein homeostasis. Chaperone proteins maintain proper protein folding in the cell by utilizing a variety of distinct, characteristic mechanisms to prevent aberrant intermolecular interactions, prevent protein aggregation, and lower entropic costs to allow for protein refolding. Continued study has found that chaperones may exhibit alternative functions, including maintaining protein folding during endoplasmic reticulum (ER) import and chaperone-mediated degradation, among others. Alternative chaperone functions are frequently controlled by post-translational modification, in which a given chaperone can switch between functions through covalent modification. This review will focus on the Hsp70 class chaperones and their Hsp40 co-chaperones, specifically highlighting the importance of post-translational control of chaperones. These modifications may serve as a target for therapeutic intervention in the treatment of diseases of protein misfolding and aggregation

The Purification and Characterization of N-terminally Acetylated Ssal from Saccharomyces cerevisiae

Molecular chaperones are highly conserved, ubiquitous enzymes that maintain proteostasis by mediating protein structure in vivo. Post-translational modifications (PTMs) can act as a functional switch between chaperone pathways, allowing for cells to enact a coordinated response to cellular perturbations. Several PTMs are well characterized in the context of chaperone function, though the role of N-terminal acetylation is commonly overlooked, leading to an overwhelming lack of scientific understanding in this area of study. Ssa1, a Hsp70 class chaperone endogenous to Saccharomyces cerevisiae, is likely N-terminally acetylated, though in vitro studies of Ssa1 are limited by current purification methods which are resource-intensive. To address these limitations, we developed a one-step purification scheme that uses a Protein-A fusion transformant strain in combination with IgG-conjugated magnetic Dynabeads to facilitate Ssa1 pull-down. Using this method, Ssa1 was natively isolated in high purity and yield while retaining its activity and our modification of interest. This study also established the basis for evaluating differences Ssa1 chaperone activity due to disruption of N-terminal acetylation by purifying Ssa1 in N-terminal acetylation deficient backgrounds. Through the expression and purification of the Ssa1 co-chaperone, Ydj1, this study has additionally provided components needed to facilitate future co-chaperone binding experiments, which will help determine the contribution of N-terminal acetylation to Hsp70 chaperone activity and efficiency

On the N3O2- paradigm

A survey of the existing experimental and theoretical data on the trinitrogen dioxide anion N3O2- that manifests a controversy as to the number of isomers and their chemical structures is presented. To resolve the controversy, new computational studies are performed at the MP2/aug-cc-pVTZ computational level. Two hitherto unknown isomers are predicted, one with singlet and one with triplet spin multiplicity. The singlet isomer, structurally characterized as N-2 center dot[ONO](-), is the most stable among all known isomers and accounts for fragmentation patterns observed in the recent dissociative photodetachment experiments. (C) 2007 Elsevier B.V. All rights reserved

Schrock type transition metal complex formation of push-pull substituted phosphanyl-carbenes, a quantum chemical investigation by density-functional methods

Schoeller W, Rozhenko AJB, Alijah A. Schrock type transition metal complex formation of push-pull substituted phosphanyl-carbenes, a quantum chemical investigation by density-functional methods. JOURNAL OF ORGANOMETALLIC CHEMISTRY. 2001;617-618(1):435-443.The formation of coordination compounds of phosphanyl carbenes with a transition metal in a high oxidation state (Schrock type) is evaluated by density functional theory. In the Schrock type carbene complexes the transition metal-carbon bond possesses a multiple bond character. If one of the ligands at the carbene center possesses a leaving ability, e.g. as the diaminophosphenium unit, a facile distortion to a new type of an anionic metallaalkylidene donor-acceptor complex with a diaminophosphenium cation is predicted. (C) 2001 Elsevier Science B.V. All rights reserved