Conformational Influence on the Type of Stabilization of Sulfur Radical Cations in Cyclic Peptides

Hug, Gordon L.; Bobrowski, Krzysztof; Pogocki, Dariusz; Hörner, Gerald; Marciniak, Bronisław

doi:10.1002/cphc.200700369

Cited by 27 publications

(41 citation statements)

References 29 publications

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“…However, one problem that persisted was the difficulty of determining minor products that had spectral shapes and positions in somewhat different places than those of the major species, yet whose spectral features were still in some sense close to those of the major species [16]. In these cases, it was difficult to determine if the minor species was in fact present, or whether the reference spectra for the major species was not quite correct.…”

Section: Contrasting Multilinear Regression and Factor Analysismentioning

confidence: 96%

“…The reference transient spectra were taken from analogous species (as in [16]), and the results suggested that (S;S) ? , neutral (S;N), and (aS) were likely present in the time range of 10-90 ls following the electron pulse.…”

Section: Application To Pulse Radiolysis Of Cyclic Dipeptidesmentioning

confidence: 99%

“…Figure 2 shows the results of four target tests for transients following the pulse radiolysis of 0.2 mM cyclo-(D-Met-L-Met) in N 2 O-saturated solutions at pH 4.27. The inputs to the target tests were the reference spectra (x l ) that were used recently in the previous works [15,16]. The original data matrix D was generated from 9 time windows at 10 ls apart from 10 to 90 ls.…”

Section: Application To Pulse Radiolysis Of Cyclic Dipeptidesmentioning

confidence: 99%

“…Recently, studies were undertaken on the hydroxyl radical oxidation of three methionine-containing cyclic dipeptides [15,16]. There is a wealth of reference spectra of optically absorbing analogous transients, each associated with the anticipated intermediates shown in Chart 1 for the cyclo-(D-Met-L-Met) optical isomer of the Met-Met cyclic dipeptide.…”

Section: Introductionmentioning

confidence: 99%

“…In effect, this dipeptide might be taken as a model for interactions of any sulfur radical cation with the heteroatoms in the peptide bonds of proteins. In addition, the particular unoxidized substrate of the radicals in Chart 1 allowed for an investigation [15,16] of the interaction of suspected bond formation between the oxidized and unoxidized sulfurs on adjacent methionine residues in the interior of proteins, i.e. calmodulin [17].…”

Section: Introductionmentioning

confidence: 99%

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Factor analysis of transient spectra. Free radicals in cyclic dipeptides containing methionine

et al. 2009

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Factor analysis is introduced and applied to resolving puzzling behavior in the free-radical chemistry of the cyclic dipeptide cyclo-(D-Met-L-Met). Previously, spectral analysis of the transient absorption spectra, following the hydroxyl radical-induced oxidation of cyclo-(D-Met-L-Met), failed to match expectations seen when transient conductivity was used to monitor the same reaction sequence. In the current work, factor analysis is used to show that a radical cation is formed via the stabilization of the oxidized sulfur through the formation of two-centered three-electron bonds with the lone pairs on oxygen. This previously undetected radical resolves the discrepancy between transient absorption and transient conductivity observations.

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Section: Contrasting Multilinear Regression and Factor Analysismentioning

confidence: 96%

Section: Application To Pulse Radiolysis Of Cyclic Dipeptidesmentioning

confidence: 99%

Section: Application To Pulse Radiolysis Of Cyclic Dipeptidesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Factor analysis of transient spectra. Free radicals in cyclic dipeptides containing methionine

et al. 2009

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Radiation‐Induced Radical Reactions

Bobrowski

2012

Encyclopedia of Radicals in Chemistry, Biology and Materials

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This article reports on radiation‐induced radical reactions in gases, liquids, and solids. A brief summary of specific features of high‐energy radiation and its interaction with matter is given as a base for better understanding of reaction mechanisms initiated by radiation. The first section describes the most important features of radiolysis in a gas phase with presentation of the commonly used gas systems for inducing and studying radical reactions. Relevant examples include radical reactions connected with atmospheric and environmental chemistry, combustion, and electric discharges. The second section focuses on radiation‐induced radical reactions in water and aqueous solutions with a special emphasis on procedures that allow induction of radical reactions in a controlled manner. Relevant examples include radical reactions initiated by primary and secondary radicals from water radiolysis with a variety of compounds. Application of various organic solvents and ionic liquids offering a convenient method of generation and also some control over the nature of radical ions and excited states formed in the irradiated solvents and derived from the solutes is also presented. The last section briefly summarizes the most commonly applied solid systems and highlights radiation‐induced radical reactions in zeolites, a new matrix used recently for radiation generation of radicals and radical ions in the solid state.

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Oxygen Delivery as a Limiting Factor in Modelling Dicopper(II) Oxidase Reactivity

Gülzow

Hörner

Strauch

et al. 2017

Chemistry A European J

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What is the most significant result of this study? Attempts to mimic metalloenzymes teach us about catalysis, and the lessons learnt find widespread application in an umber of chemical disciplines, including process engineering. Our catechol oxidase models show an unprecedented dependence of their reactivity on the method of oxygen administration:w hen going beyond the limits of homogeneously distributed reactants, by administering surplus dioxygen periodically during catalytic turnover, we observed reactivities increasing by factors of five to ten, in comparison with the well-established conditions of dioxygen saturation. This observation is not limited to our new system. Reference experiments with systems taken from the literature suggest that the effect, which is of interest in the context of reactive bubbly flows, is general, but has hitherto gone unnoticed. What was the inspiration for this cover design? When we were invited to submit ad esign, we took inspiration from the fact that the browning of cut fruit is effected by copper-and oxygen-dependent oxygenases, leading to melanine pigments, which are polymeric ortho-quinone derivatives. An abstract rendering of our dinuclear copper(II) complexes is shown in the foreground at left. In our cover art, as till life by Gabriele Endres, the browning of the half-eaten apple in the foreground denotes the enhanced reaction of our model substrate, ac atechol, under oxygen-enriched conditions, as provided by ab ubbly flow of oxygen. What other topics are you working on at the moment? We are interested in the activation of dioxygen and its exploitation as an environmentally benign, or green, oxidant, using bioinspired transition-metal complexes of tailor-made ligands. Our "workhorse" metal ions are iron and copper,i nt heir various oxidation states, and we are currently making our first forays into the coordination chemistry of manganese. Our ligands are polypodal, including tetra-and pentadentate ligands, as in the present work, or extended -tripodal hexadentate, as in recent spin-state dynamics studies. The former chelators shield am ajor part of the metal-coordination sphere, focusing the reactivity on one or two "labile" coordination sites. The coordinative strain of all these claw-like ligands can also be varied, enabling investigations, in which distortions of the coordination sphere and their influence on complex reactivity and spin multiplicity,c an be studied in isolation (and with reference to the concept of the entatic state). Invited for the cover of this issue is the group of Gerald Hçrner and Andreas Grohmann at the Technical University of Berlin. The image depicts that the browning of cut fruit is effected by copper-and oxygen-dependent oxygenases, leading to mela-nine pigments, which are polymeric ortho-quinone derivatives.R ead the full text of the article at

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Conformational Influence on the Type of Stabilization of Sulfur Radical Cations in Cyclic Peptides

Cited by 27 publications

References 29 publications

Factor analysis of transient spectra. Free radicals in cyclic dipeptides containing methionine

Factor analysis of transient spectra. Free radicals in cyclic dipeptides containing methionine

Radiation‐Induced Radical Reactions

Oxygen Delivery as a Limiting Factor in Modelling Dicopper(II) Oxidase Reactivity

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