Diffraction Studies of Photoexcited Crystals:  Metastable Nitrosyl-Linkage Isomers of Sodium Nitroprusside

Carducci, Michael D.; Pressprich, M. R.; Coppens, Philip

doi:10.1021/ja9625743

Cited by 312 publications

(335 citation statements)

References 55 publications

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“…The light-induced structural change can be illustrated by a photodifference map (Carducci et al, 1997), which shows the change in electron density upon light exposure and is obtained by Fourier summation with coef®cients equal to the difference between the`on' and`off' structure factors. To construct the photodifference map, the four data sets were brought on a common temperature scale using the ÁB values from the Wilson plot, on a proper relative scale with the Scalepack programs (Otwinowski & Minor, 1997) and on an absolute scale by re®nement of the conventional scale factors against the basic structure.…”

Section: Analysis Of the Resultsmentioning

confidence: 99%

Excited-state structure by time-resolved X-ray diffraction

Kim

Pillet

et al. 2002

Acta Crystallogr A Found Crystallogr

177

131

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X-ray crystallography has traditionally been limited to the study of the groundstate structure of molecules and solids. 2À ], performed at helium temperatures with synchrotron radiation. The shortening of the PtÐPt bond by 0.28 (9) A Ê upon excitation is compatible with the proposed mechanism involving promotion of a PtÐPt antibonding d'* electron to a weakly bonding p orbital. The contraction is accompanied by a 3 molecular rotation. The time-resolved diffraction technique described here is applicable to reversible light-driven processes in the crystalline solid state.

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Section: Analysis Of the Resultsmentioning

confidence: 99%

Excited-state structure by time-resolved X-ray diffraction

Kim

Pillet

et al. 2002

Acta Crystallogr A Found Crystallogr

177

131

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“…Figure 3 shows the two spectra and their deconvolution for a population Psi of SI of about 41%. We observed one new band in the red spectral range around 13200 cnf The fitted parameters of this transition of SI are given in Table II. In the literature the metastable state SI is explained by an elongation of the N-C-bond distances [61 or an inversion of the N-C-bond [7]. In the inversion model the ground state configuration Fe-N-C is inverted by 180' to Fe-O-N in SI.…”

Section: Resultsmentioning

confidence: 99%

Optical absorption spectroscopy in the metastable state SI of Na₂[Fe(CN)₅NO]·2H₂O

et al. 2001

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The metastable state SI in single crystals of orthorhombic Na 2 [Fe(CN) 5 NO].2H 2 0 (sodiumnitroprusside, SNP) was investigated by absorption spectroscopy. The development of the spectra with increasing population of SI was monitored and a new band in the red spectral range was assigned to SI. By comparing with density functional theory (DFT) calculations we were able to assign the band to the electronic transition 2b 2 --->7e. In addition we found that very strong holographic light scattering influences the absorption spectra measured with light polarization along the a-or b-axis of the crystals.

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“…The HNO adduct is depicted as N bound, as found in characterized end-on HNO-metal complexes (58). There is much recent evidence for O-bound linkage isomers of metal-nitrosyls, termed isonitrosyls, but these are typically only observed after photolysis at low temperature within a solid or crystalline material (59)(60)(61)(62). The analogous O-bound HNO, isonitroxyl, has never been characterized to our knowledge; theorectical calculations have predicted the O-bound isonitroxyl adduct of Fe porphyrinates would be over 50 kJ∕mol higher in energy than the corresponding N-bound nitroxyl (63).…”

Section: Discussionmentioning

confidence: 99%

Nitrosyl hydride (HNO) replaces dioxygen in nitroxygenase activity of manganese quercetin dioxygenase

Kumar

Zapata

Ramirez

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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Quercetin dioxygenase (QDO) catalyzes the oxidation of the flavonol quercetin with dioxygen, cleaving the central heterocyclic ring and releasing CO. The QDO from Bacillus subtilis is unusual in that it has been shown to be active with several divalent metal cofactors such as Fe, Mn, and Co. Previous comparison of the catalytic activities suggest that Mn(II) is the preferred cofactor for this enzyme. We herein report the unprecedented substitution of nitrosyl hydride (HNO) for dioxygen in the activity of Mn-QDO, resulting in the incorporation of both N and O atoms into the product. Turnover is demonstrated by consumption of quercetin and other related substrates under anaerobic conditions in the presence of HNO-releasing compounds and the enzyme. As with dioxygenase activity, a nonenzymatic base-catalyzed reaction of quercetin with HNO is observed above pH 7, but no enhancement of this basal reactivity is found upon addition of divalent metal salts. Unique and regioselective N-containing products ( 14 N∕ 15 N) have been characterized by MS analysis for both the enzymatic and nonenzymatic reactions. Of the several metallo-QDO enzymes examined for nitroxygenase activity under anaerobic condition, only the Mn(II) is active; the Fe(II) and Co(II) substituted enzymes show little or no activity. This result represents an enzymatic catalysis which we denote nitroxygenase activity; the unique reactivity of the Mn-QDO suggests a metalmediated electron transfer mechanism rather than metal activation of the substrate's inherent base-catalyzed reactivity.nitroxyl | quercetinase D ioxygenases are enzymes that incorporate both atoms of dioxygen into a targeted substrate, e.g., the enzyme catechol 1,2-dioxygenase cleaves the C-C bond between catechol's two hydroxyl groups forming the dicarboxylate cis,cis-muconic acid (1). Although highly divergent, there are two broadly defined classes of nonheme dioxygenases: those that directly bind dioxygen at the metal center or those in which dioxygen binds to the substrate that has been activated by interaction with the metal center (2). Such questions also apply to quercetin dioxygenase (QDO), which catalyzes the oxidation of the flavonol quercetin (1) with dioxygen ( Fig. 1). During turnover, QDO cleaves the central heterocyclic ring of quercetin, releasing CO, and yielding the corresponding depside. The QDO from Bacillus subtilis is unusual in that it has been shown to be active with several divalent metal cofactors such as Cu, Fe, Mn, and Co. Comparison of the catalytic activities suggest that Mn(II) is the preferred cofactor for this enzyme (3).The simple molecule nitrosyl hydride (HNO) is the singly reduced and protonated form of nitric oxide, NO. HNO has garnered much interest because it demonstrates a physiological reactivity distinctly different from its congener nitric oxide (4, 5). In a series of papers, we have reported the preparation and characterization of the HNO adduct of myoglobin (HNO-Mb) by reduction of 7) and by trapping of free HNO by deoxymyoglobin (Mb-Fe II ) (8)...

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Diffraction Studies of Photoexcited Crystals: Metastable Nitrosyl-Linkage Isomers of Sodium Nitroprusside

Cited by 312 publications

References 55 publications

Excited-state structure by time-resolved X-ray diffraction

Excited-state structure by time-resolved X-ray diffraction

Optical absorption spectroscopy in the metastable state SI of Na₂[Fe(CN)₅NO]·2H₂O

Nitrosyl hydride (HNO) replaces dioxygen in nitroxygenase activity of manganese quercetin dioxygenase

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Diffraction Studies of Photoexcited Crystals: Metastable Nitrosyl-Linkage Isomers of Sodium Nitroprusside

Cited by 312 publications

References 55 publications

Excited-state structure by time-resolved X-ray diffraction

Excited-state structure by time-resolved X-ray diffraction

Optical absorption spectroscopy in the metastable state SI of Na2[Fe(CN)5NO]·2H2O

Nitrosyl hydride (HNO) replaces dioxygen in nitroxygenase activity of manganese quercetin dioxygenase

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Optical absorption spectroscopy in the metastable state SI of Na₂[Fe(CN)₅NO]·2H₂O