Collisional removal of NO (B 2Π, v=2 and 3) at 230 K

Hwang, Eunsook S.; Lacoursière, Jean; Copeland, Richard A.; Slanger, T. G.

doi:10.1063/1.474813

Cited by 30 publications

(75 citation statements)

References 22 publications

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“…The thermocouple tip is located ϳ4 mm away from the intersection of the two laser beams. Based on previous checks, the thermocouple temperature reading has an accuracy better than ϳ10 K. 3,10,11 The excitation of ground-state O 2 molecules to the b 1 ⌺ g ϩ state is achieved by a tunable dye laser pumped by a frequency-doubled Nd:YAG laser. Direct one-photon excitation to the O 2 (b 1 ⌺ g ϩ ,ϭ2) level has been used in several collisional energy transfer studies.…”

Section: Methodsmentioning

confidence: 99%

Collisional removal of O2(b 1Σg+,υ=2,3)

Kalogerakis

Copeland

Slanger

2002

The Journal of Chemical Physics

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The temperature dependence of the collisional removal of O 2 in the ϭ3 level of the b 1 ⌺ g ϩ state by N 2 , O 2 , and CO 2 was investigated at room temperature and below. Measurements on the ϭ2 level with the colliders, O 2 , N 2 O, Ar, and He are also reported. For ϭ3 removal by O 2 , the trend of sharply decreasing loss rate coefficients with increasing is seen to continue. For example, at 200 K the rate coefficient for collisional removal of O 2 from the ϭ3 level by O 2 is some three orders of magnitude smaller than that for the ϭ1 level. We argue that the mechanism of the deactivation is electronic-electronic ͑E-E͒ energy transfer. Observation of emission from a broad range of O 2 (b 1 ⌺ g ϩ ) vibrational levels in the terrestrial nightglow, recently discovered in astronomical sky spectra, show less than an order of magnitude difference in population between the more highly populated ϭ3 level and the less populated ϭ1 level. The implications of these two observations on the vibrational-level-specific atmospheric sources of vibrationally excited molecules in the b 1 ⌺ g ϩ electronic state are explored.

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Section: Methodsmentioning

confidence: 99%

Collisional removal of O2(b 1Σg+,υ=2,3)

Kalogerakis

Copeland

Slanger

2002

The Journal of Chemical Physics

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“…Besides the three Cys residues required for [Fe 4 S 4 ]‐cluster binding, H124, E126, S221, and N223 (H124, E126, S225, and N227 in Escherichia coli IspH) were found to have very high conservation scores, and these residues are indeed essential for IspH catalysis according to the results of site‐directed mutagenesis 19. 24…”

Section: Structures Of Isph and Ispgmentioning

confidence: 99%

“…How IspH catalyzes the “reductive dehydroxylation” of HMBPP ( 4 ) has been a mystery for nearly a decade, and seven mechanisms have been proposed, with carbocation, carbanion, and carbon‐radical reaction intermediates 13–15. 19, 46–49 Recent spectroscopic studies found no evidence for any radical species50 and point to a “bioorganometallic” mechanism involving direct iron–carbon interactions during catalysis,24, 50 as summarized in Scheme . The trapping and characterization of three putative intermediates led to reaction‐mechanism proposals based on EPR spectroscopic studies and density functional theory (DFT) calculations as well as Mössbauer spectroscopic, X‐ray crystallographic, and stereochemical results.…”

Section: The Catalytic Mechanism Of Isphmentioning

confidence: 99%

Bioorganometallic Chemistry with IspG and IspH: Structure, Function, and Inhibition of the [Fe₄S₄] Proteins Involved in Isoprenoid Biosynthesis

Wang

Oldfield

2014

Angew Chem Int Ed

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The methylerythritol phosphate pathway of isoprenoid biosynthesis is an attractive anti-infective drug target. The last two enzymes of this pathway, IspG and IspH, are [Fe4S4] proteins not produced by humans that catalyze 2H+/2e− reductions with novel mechanisms. In this review, we summarize recent advances in structural, mechanistic and inhibitory studies of these two enzymes. In particular, mechanistic proposals involving bioorganometallic intermediates are presented and compared with other mechanistic possibilities, and inhibitors based on substrate analogs, developed by rational design and compound library screening, are discussed. These results represent the first examples of bioorganometallic catalytic mechanisms of [Fe4S4] enzymes, and open up new routes to inhibitor design targeting [Fe4S4] clusters.

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“…In our group's earlier studies of NO collisional kinetics using the same flow cell, the NO rotational distribution was used to quantify the thermocouple's accuracy, which has been estimated to be ±8 K. 39,42 The ozone photolysis products have significant kinetic energy and their thermalization in collisions with the bath gas produces a transient heating effect. The kinetic energy released in photolysis at 285 nm averaged over all photolysis channels (2a, b) is roughly 0.5 eV per photolysis event.…”

Section: Experimental Approachmentioning

confidence: 99%

Collisional relaxation of O2($X^3\Sigma _g^ -$X3Σg−, υ = 1) and O2(a1Δg, υ = 1) by atmospherically relevant species

Pejaković

Campbell

Kalogerakis

et al. 2011

The Journal of Chemical Physics

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Laboratory measurements are reported of the rate coefficient for collisional removal of O(2)(X(3)Σ(g)(-), υ = 1) by O((3)P), and the rate coefficients for removal of O(2)(a(1)Δ(g), υ = 1) by O(2), CO(2), and O((3)P). A two-laser method is employed, in which the pulsed output of the first laser at 285 nm photolyzes ozone to produce oxygen atoms and O(2)(a(1)Δ(g), υ = 1), and the output of the second laser detects O(2)(a(1)Δ(g), υ = 1) via resonance-enhanced multiphoton ionization. The kinetics of O(2)(X(3)Σ(g)(-), υ = 1) + O((3)P) relaxation is inferred from the temporal evolution of O(2)(a(1)Δ(g), υ = 1), an approach enabled by the rapid collision-induced equilibration of the O(2)(X(3)Σ(g)(-), υ = 1) and O(2)(a(1)Δ(g), υ = 1) populations in the system. The measured O(2)(X(3)Σ(g)(-), υ = 1) + O((3)P) rate coefficient is (2.9 ± 0.6) × 10(-12) cm(3) s(-1) at 295 K and (3.4 ± 0.6) × 10(-12) cm(3) s(-1) at 240 K. These values are consistent with the previously reported result of (3.2 ± 1.0) × 10(-12) cm(3) s(-1), which was obtained at 315 K using a different experimental approach [K. S. Kalogerakis, R. A. Copeland, and T. G. Slanger, J. Chem. Phys. 123, 194303 (2005)]. For removal of O(2)(a(1)Δ(g), υ = 1) by O((3)P), the upper limits for the rate coefficient are 4 × 10(-13) cm(3) s(-1) at 295 K and 6 × 10(-13) cm(3) s(-1) at 240 K. The rate coefficient for removal of O(2)(a(1)Δ(g), υ = 1) by O(2) is (5.6 ± 0.6) × 10(-11) cm(3) s(-1) at 295 K and (5.9 ± 0.5) × 10(-11) cm(3) s(-1) at 240 K. The O(2)(a(1)Δ(g), υ = 1) + CO(2) rate coefficient is (1.5 ± 0.2) × 10(-14) cm(3) s(-1) at 295 K and (1.2 ± 0.1) × 10(-14) cm(3) s(-1) at 240 K. The implications of the measured rate coefficients for modeling of atmospheric emissions are discussed.

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Collisional removal of NO (B 2Π, v=2 and 3) at 230 K

Cited by 30 publications

References 22 publications

Collisional removal of O2(b 1Σg+,υ=2,3)

Collisional removal of O2(b 1Σg+,υ=2,3)

Bioorganometallic Chemistry with IspG and IspH: Structure, Function, and Inhibition of the [Fe₄S₄] Proteins Involved in Isoprenoid Biosynthesis

Collisional relaxation of O2($X^3\Sigma _g^ -$X3Σg−, υ = 1) and O2(a1Δg, υ = 1) by atmospherically relevant species

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Collisional removal of NO (B 2Π, v=2 and 3) at 230 K

Cited by 30 publications

References 22 publications

Collisional removal of O2(b 1Σg+,υ=2,3)

Collisional removal of O2(b 1Σg+,υ=2,3)

Bioorganometallic Chemistry with IspG and IspH: Structure, Function, and Inhibition of the [Fe4S4] Proteins Involved in Isoprenoid Biosynthesis

Collisional relaxation of O2($X^3\Sigma _g^ -$X3Σg−, υ = 1) and O2(a1Δg, υ = 1) by atmospherically relevant species

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Bioorganometallic Chemistry with IspG and IspH: Structure, Function, and Inhibition of the [Fe₄S₄] Proteins Involved in Isoprenoid Biosynthesis