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We have performed CCSD(T), MP2, and DF-LMP2 calculations of the interaction energy of CO on the MgF2(110) surface by applying the method of increments and an embedded cluster model. In addition, we performed periodic HF, B3LYP, and DF-LMP2 calculations and compare them to the cluster results. The incremental CCSD(T) calculations predict an interaction energy of Eint = -0.37 eV with a C-down orientation of CO above a Mg2+ ion at the surface with a basis set of VTZ quality. We find that electron correlation constitutes about 50% of the binding energy and a detailed evaluation of the increments shows that the largest contribution to the correlation energy originates from the CO interaction with the closest F ions on the second layer. [ABSTRACT FROM AUTHOR]

We have combined an embedded-cluster model with an extension of the method of increments to treat the adsorption of molecules on a surface. In this way we are able to investigate the physisorption of CO on CeO2(110) at the MP2, MP4(SDTQ), and CCSD(T) levels with only moderate computational costs. We find that, at the CCSD(T) level, 25% of the adsorption energy originates from electron correlation. The interactions of the CO molecule with its five nearest cerium and oxygen neighbors in the surface layer make the largest contributions to the electron correlation. Approximately 97% of the adsorption-induced electron correlation energy part of the adsorption energy is recovered by the method of increments (in our chosen expansion), at the MP2 level. [ABSTRACT FROM AUTHOR]

Periodic density functional theory calculations were performed to investigate the Lewis acidity of unsaturated surface cations of ZnF 2 , using CO as probe molecule at different coverages. We have calculated adsorption energies for CO on all low index ZnF 2 surfaces using DFT with the B3LYP functional and subsequent dispersion correction. Additionally local second order Møller-Plesset perturbation theory (LMP2) calculations were performed. In most of the cases, the adsorption of CO on different surfaces is described well using B3LYP. Dispersion correction to B3LYP is found to overestimate the adsorption energy. The interaction among adsorbed CO molecules appears to have a significant effect on the adsorption energies at full coverage. [ABSTRACT FROM AUTHOR]

Abstract: We have characterised the Lewis acidity of unsaturated surface cations of MgF2 crystals using periodic calculations at the B3LYP level. The relative importance of low index surfaces was determined by calculating surface energies, and these surfaces were then probed by CO adsorption. We found that a MgF2 microcrystal should expose mainly (110), (100) and (101) surfaces in which the undercoordinated cations are fivefold coordinated. The adsorption energies and CO stretching frequencies are discussed with respect to the coordination number of surface cations and the stability of the surfaces and are compared to IR spectra from the literature. [Copyright &y& Elsevier]

The large conductance, voltage- and calcium-activated potassium channel, BK, is a known target for the gasotransmitter, carbon monoxide (CO). Activation of BK by CO modulates cellular excitability and contributes to the physiology of a diverse array of processes, including vascular tone and oxygen-sensing. Currently, there is no consensus regarding the molecular mechanisms underpinning reception of CO by the BK. Here, employing voltage-clamped, inside-out patches from HEK293 cells expressing single, double and triple cysteine mutations in the BK α-subunit, we test the hypothesis that CO regulation is conferred upon the channel by interactions with cysteine residues within the RCK2 domain. In physiological [Ca], all mutants carrying a cysteine substitution at position 911 (C911G) demonstrated significantly reduced CO sensitivity; the C911G mutant did not express altered Ca-sensitivity. In contrast, histidine residues in RCK1 domain, previously shown to ablate CO activation in low [Ca], actually increased CO sensitivity when [Ca] was in the physiological range. Importantly, cyanide, employed here as a substituent for CO at potential metal centres, occluded activation by CO; this effect was freely reversible. Taken together, these data suggest that a specific cysteine residue in the C-terminal domain, which is close to the Ca bowl but which is not involved in Ca activation, confers significant CO sensitivity to BK channels. The rapid reversibility of CO and cyanide binding, coupled to information garnered from other CO-binding proteins, suggests that C911 may be involved in formation of a transition metal cluster which can bind and, thereafter, activate BK. [ABSTRACT FROM AUTHOR]

Abstract: Applying the method of increments, we have performed MP2 and CCSD(T) calculations for the physisorption of CO on a cerium site on the ceria(111) surface. Our calculations predict an interaction energy of −0.28eV. We have compared our calculations to previous CCSD(T) calculations for the physisorption of CO on a cerium site on the ceria(110) surface and found a difference in the interaction energy that is related to the different structure of the two surfaces. On the ceria(110) surface only 30% of the interaction energy originate from electron correlation effects, but on the ceria(111) surface almost the entire binding energy (80%) is due to electron correlation effects. Analyses of the interaction energy contributions show that most of the electron correlation part originates from the interaction of CO with the O ions in the topmost surface layer. [Copyright &y& Elsevier]

Carbon monoxide (CO) is a potent activator of large conductance, calcium-dependent potassium (BKCa) channels of vascular myocytes and carotid body glomus cells or when heterologously expressed. Using the human BKCa channel α1-subunit ( hSlo1; KCNMA1) stably and transiently expressed in human embryonic kidney 293 cells, the mechanism and structural basis of channel activation by CO was investigated in inside–out, excised membrane patches. Activation by CO was concentration dependent (EC50 ∼20 μM), rapid, reversible, and evoked a shift in the V0.5 of −20 mV. CO evoked no changes in either single channel conductance or in deactivation rate but augmented channel activation rate. Activation was independent of the redox state of the channel, or associated compounds/protein partners, and was partially dependent on [Ca2+]i in the physiological range (100–1,000 nM). Importantly, CO “super-stimulated” BKCa activity even in saturating [Ca2+]i. Single or double mutation of two histidine residues previously implicated in CO sensing did not suppress CO activation but replacing the S9–S10 module of the C-terminal of Slo1 with that of Slo3 completely prevented the action of CO. These findings show that a motif in the S9–S10 part of the C-terminal is essential for CO activation and suggest that this gas transmitter activates the BKCa channel by redox-independent changes in gating. [ABSTRACT FROM AUTHOR]

Abstract: Hartree–Fock and DFT calculations are reported for the CO/CeO2(110) surface system. The electron density, electrostatic potential, atomic charges and projected electronic density of states have been calculated from an ECP-and-point-charge-embedded cluster model and is compared with periodic calculations. The agreement between the two surface models is reasonably good. A number of weakly bonding CO adsorption sites were found, with E ads (BSSE-corrected) ranging from 0.01 to 0.22 eV per adsorbed molecule. The two most favourable sites are found in the vicinity of surface cerium ions, with the CO molecule oriented in a tilted fashion, C-end down. The surface-induced CO stretching vibrational frequency shifts on these sites are a redshift of ≈−30 cm−1 and a blueshift of ≈25 cm−1, respectively. [Copyright &y& Elsevier]