Modelling The Dipole Moment Function Of Carbon Monoxide Capable Of Predicting The Rotational Distribution In The 7-0 Band

\begin{wrapfigure}{l}{0pt} \includegraphics[scale=0.1]{Band70empirical.eps} \end{wrapfigure} The rotational distributions of the intensities in the low-v vibrational bands are nearly insensitive to the specific forms of the PEFs and DMFs based on the experimental and/or \textit{ab initio} data. This is not the case for the higher overtone bands. We discuss the problem: Which properties should the model PEF and DMF possess in order to be capable of predicting the intensities of the yet unobserved lines? Arguments are presented that the Born-Oppenheimer PEF and DMF should possess some features following from their properties as functions of the inter-atomic separation as a complex variable. In particular, they must contain branch points associated with the crossings between the ground and excited electronic states. This approach implies that both functions are to be fitted simultaneously to the common data set including both the line positions and the intensities. However, such a problem is very difficult to solve. Here and in Ref. (1), in application to CO, we assume that the PEF is given (2), and we develop an irregular DMF form containing two branch points corresponding to the expected crossings in the complex plane near 0.4 and {2.2 \AA}. We compare it with an alternative regular function (1) and find that the rotational distribution in the vibrational 7-0 band predicted by the former is very stable with respect to small variations in the data base, as opposed to the regular DMF showing strong instability. The predicted intensities (see figure) are stronger than the HITRAN values calculated by Li et al. (3) with a combined empirical/spline-interpolated \textit{ab initio} DMF but are close to the ones calculated by us with the purely empirical DMF of Li et al. The irregular function is expected to provide for a reliable prediction of the ro-vibrational line intensities in the 7-0 band. This work was performed in accordance with the state task, state registration No. AAAA-A19-119071190017-7. (1) V. V. Meshkov, A. V. Stolyarov, A. Yu. Ermilov, E. S. Medvedev, V. G. Ushakov, I. E. Gordon, JQSRT (in preparation); (2) JQSRT 217 (2018 ) 262-273. (3) G. Li, I. E. Gordon, L. S. Rothman, Y. Tan, S.-M. Hu, S. Kassi, A. Campargue, E. S. Medvedev, Astrophys. J., Suppl. Ser. 216 (2015) 15

Mechanism of long-range proton translocation along biological membranes

AbstractRecent experiments suggest that protons can travel along biological membranes up to tens of micrometers, but the mechanism of transport is unknown. To explain such a long-range proton translocation we describe a model that takes into account the coupled bulk diffusion that accompanies the migration of protons on the surface. We show that protons diffusing at or near the surface before equilibrating with the bulk desorb and re-adsorb at the surface thousands of times, giving rise to a power-law desorption kinetics. As a result, the decay of the surface protons occurs very slowly, allowing for establishing local gradient and local exchange, as was envisioned in the early local models of biological energy transduction

Theoretical and computational analysis of the membrane potential generated by cytochrome c oxidase upon single electron injection into the enzyme

AbstractWe have developed theory and the computational scheme for the analysis of the kinetics of the membrane potential generated by cytochrome c oxidase upon single electron injection into the enzyme. The theory allows one to connect the charge motions inside the enzyme to the membrane potential observed in the experiments by using data from the “dielectric topography” map of the enzyme that we have created. The developed theory is applied for the analysis of the potentiometric data recently reported by the Wikström group [I. Belevich, D.A. Bloch, N. Belevich, M. Wikström and M.I. Verkhovsky, Exploring the proton pump mechanism of cytochrome c oxidase in real time, Proc. Natl. Acad. Sci. U. S. A. 104 (2007) 2685–2690] on the O to E transition in Paracoccus denitrificans oxidase. Our analysis suggests, that the electron transfer to the binuclear center is coupled to a proton transfer (proton loading) to a group just “above” the binuclear center of the enzyme, from which the pumped proton is subsequently expelled by the chemical proton arriving to the binuclear center. The identity of the pump site could not be determined with certainty, but could be localized to the group of residues His326 (His291 in bovine), propionates of heme a3, Arg 473/474, and Trp164. The analysis also suggests that the dielectric distance from the P-side to Fe a is 0.4 or larger. The difficulties and pitfalls of quantitative interpretation of potentiometric data are discussed

Empirical normal intensity distribution for overtone vibrational spectra of triatomic molecules

Theoretical calculations are contributing a significantly higher proportion of data to contemporary spectroscopic databases, which have traditionally relied on experimental observations and semi-empirical models. It is now a common procedure to extend calculated line lists to include ro-vibrational transitions between all bound states of the ground electronic state up to the dissociation limit. Advanced ab initio methods are utilized to calculate the potential energy and dipole moment surfaces (PESs and DMSs), and semi-empirical PESs are then obtained by combining ab initio and experimental data. The objective is to reach high accuracy in the calculated transition intensities for all parts of spectrum, i.e. to increase the predictive power of the model. We show that in order to perform this task, one needs, in addition to the standard improvements of the PES and DMS in the spectroscopically accessible regions, to extend the ab initio calculations of the PES towards the united-atom limit along the stretching coordinates. The argument is based on the correlation between the intensities of high-overtone transitions and the repulsive potential wall that has previously been theoretically established for diatomic molecules and is empirically extended here to linear and nonlinear triatomic molecules. We generate partial line lists for water and ozone, and together with an already available line list for carbon dioxide, we derive the normal intensity distribution, which is a direct consequence of this correlation. The normal distribution is not an instrument to compute highly accurate intensities, rather it is a means to analyze the intensities computed by the traditional methods

HUND'S CASE (a)-CASE (b) TRANSITION IN THE SINGLET-TRIPLET SPECTRUM OF PRYAZINE IN A SUPERONIC JET,∗JET,^{*}

$^{*}$ Work supported by the U.S. NAS/NRC CAST Program, by the U.S. National Science Foundation (CHE-9224398), by the International Science Foundation (SDQ000, NJ6000, NJ6300), and by the Russian Foundation for Basic Research (95-03-08 130a)Author Institution: Institute of Chemical Physics, Russian Academy of Sciences; Department of Chemistry, University of PitsburghWe report theoritical calculations of the $T_{1}-S_{0}$ excitation spectrum of pyrazine, pyrazine-$d_{4}$, and the pyrazine-Arvan der Waals complex. Towards this end, a closed analytical formula for the intensities of individual rovibronic transitions has been derived. The triplet state Hamiltonian includes, in addition to the usual rigid rotor terms, both intramanifold spin-spin coupling and intermanifold spin-orbit coupling. Taking reasonable values for these parametres leads to several experimental predictions, including a transition from Hund#### Case (a) to Case (b) with increasing J and the apperance of fine structure splittings at even moderate spectral resolution. Detailed examples will be discussed

Proton transport via the membrane surface.

Some proton pumps, such as cytochrome c oxidase (C(c)O), translocate protons across biological membranes at a rate that considerably exceeds the rate of proton transport to the entrance of the proton-conducting channel via bulk diffusion. This effect is usually ascribed to a proton-collecting antenna surrounding the channel entrance. In this paper, we consider a realistic phenomenological model of such an antenna. In our model, a homogeneous membrane surface, which can mediate proton diffusion toward the channel entrance, is populated with protolytic groups that are in dynamic equilibrium with the solution. Equations that describe coupled surface-bulk proton diffusion are derived and analyzed. A general expression for the rate constant of proton transport via such a coupled surface-bulk diffusion mechanism is obtained. A rigorous criterion is formulated of when proton diffusion along the surface enhances the transport. The enhancement factor is found to depend on the ratio of the surface and bulk diffusional constants, pK(a) values of surface protolytic groups, and their concentration. A capture radius for a proton on the surface and an effective size of the antenna are found. The theory also predicts the effective distance that a proton can migrate on the membrane surface between a source (such as CcO) and a sink (such as ATP synthase) without fully equilibrating with the bulk. In pure aqueous solutions, protons can travel over long distances (microns). In buffered solutions, the travel distance is much shorter (nanometers); still the enhancement effect of the surface diffusion on the proton flow to a target on the surface can be tens to hundreds at physiological buffer concentrations. These results are discussed in a general context of chemiosmotic theory

ROVIBRATIONAL LINE LISTS FOR NINE ISOTOPOLOGUES OF THE CO MOLECULE IN THE X-1 Sigma(+) GROUND ELECTRONIC STATE

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