Mechanism Of Oxidative Cleavage Research Articles

FTIR and UV/vis as methods for evaluation of oxidative degradation of model paper: DFT approach for carbonyl vibrations

The oxidative route of cellulose degradation during artificial ageing of paper in humid air (RH 59%, 90 °C) has been followed by FTIR and UV/vis spectroscopic methods providing a vibrational pattern of carbonyl groups and electronic transitions of chromophores, respectively. Conjugated ketonic groups with vibrational modes around 1610 cm −1 were correlated to the chromophores emerging in the range between 230 and 440 nm detected by UV/vis spectroscopy. The FTIR spectra of degraded cellulose were interpreted using quantum-chemical modelling based on the DFT method performed on the model molecule of cellopentose. Based on this carbonyl FTIR bands were assigned to specific vibrations. The UV/vis and FTIR correlations together with the theoretical charge distribution rationalized the possible mechanism of oxidative glycosidic bond cleavage.

Chiral preference of l-tryptophan derived metal-based antitumor agent of late 3d-metal ions (Co(II), Cu(II) and Zn(II)) in comparison to d- and dl-tryptophan analogues: Their in vitro reactivity towards CT DNA, 5′-GMP and 5′-TMP

To evaluate the biological preference of chiral drugs for molecular target DNA, new potential metal-based chemotherapeutic agents 1– 3 ( a– c) of late 3d-transition metals derived from l form, d form, and dl-tryptophan, respectively were synthesized and thoroughly characterized. Interaction studies of 1– 3 ( a– c) with CT DNA, 5′GMP and 5′-TMP have been carried out. The results reveal that the extent of DNA binding of l form of copper 2a was greatest in comparison to rest of complexes via electrostatic interaction. This was further confirmed by nuclease activity of 2a with supercoiled pBR322 DNA and it was observed that cleavage reaction involves various oxygen species and superoxide radicals by oxidative cleavage mechanism. The complex 2a exhibited significant antitumor activity against MCF-7 cell line.

DNA interaction studies of new nano metal based anticancer agent: validation byspectroscopic methods

A new nano dimensional heterobimetallic Cu–Sn containing complex as a potentialdrug candidate was designed, synthesized and characterized by analytical andspectral methods. The electronic absorption and electron paramagnetic resonanceparameters of the complex revealed that the Cu(II) ion exhibits a square pyramidalgeometry with the two pyrazole nitrogen atoms, the amine nitrogen atom andthe carboxylate oxygen of the phenyl glycine chloride ligand located at theequatorial sites and the coordinated chloride ion occupying an apical position. 119Sn NMR spectral data showed a hexa-coordinated environment around the Sn(IV) metal ion. TEM,AFM and XRD measurements illustrate that the complex could induce the condensation ofCT-DNA to a particulate nanostructure. The interaction of the Cu–Sn complex withCT-DNA was investigated by UV–vis absorption and emission spectroscopy, as well ascyclic voltammetric measurements. The results indicated that the complex interacts withDNA through an electrostatic mode of binding with an intrinsic binding constantKb = 8.42 × 104 M − 1. The Cu–Sn complex exhibits effective cleavage of pBR322 plasmid DNA by an oxidativecleavage mechanism, monitored at different concentrations both in the absence and in thepresence of reducing agents.

Copper(II) complexes of methylated glycine derivatives: Effect of methyl substituent on their DNA binding and nucleolytic property

A set of copper(II) complexes of glycine and methylated glycine derivatives, Cu(aa) 2, consisting of C-dimethylglycine, l-alanine, N-dimethylglycine and sarcosine, was investigated for their DNA binding and nucleolytic properties by means of EPR and visible spectroscopy, and electrophoresis. They bind weakly to DNA with apparent binding constants in the range 1.8–2.9 × 10 3 M −1 with very similar orientation. No DNA cleavage is observed in the absence of exogenous agents. Copper(II) complexes of N-methylated derivatives bind to DNA more stereo-specifically and less strongly, and their oxidative DNA cleavage is less efficient than those of the corresponding C-methylated derivatives in the presence of hydrogen peroxide (H 2O 2) alone, or sodium ascorbate (NaHA) alone or tandem H 2O 2–NaHA. The oxidative DNA cleavage mechanism in the three systems involves a common copper(I) species. Neocuproine can inhibit DNA cleavage by these complexes.

Identification of bacterial carotenoid cleavage dioxygenase homologues that cleave the interphenyl alpha,beta double bond of stilbene derivatives via a monooxygenase reaction.

Carotenoid cleavage oxygenases (CCOs), which are also referred to as carotenoid cleavage dioxygenases (CCDs) are a new class of nonheme iron-type enzymes that oxidatively cleave double bonds in the conjugated carbon chain of carotenoids. The oxidative cleavage mechanism of these enzymes is not clear, and both monooxygenase and dioxygenase mechanisms have been proposed for different carotenoid cleavage enzymes. CCOs have been described from plants, animals, fungi, and cyanobacteria, but little is known about their distribution and activities in bacteria other than cyanobacteria. We surveyed bacterial genome sequences for CCO homologues and report the characterization of CCO homologues that were identified in Novosphingobium aromaticivorans DSM 12444 (NOV1 and NOV2) and in Bradyrhizobium sp. (BRA-J and BRA-S). In vitro and in vivo assays with carotenoid and stilbene compounds were used to investigate the cleavage activities of the recombinant enzymes. The NOV enzymes cleaved the interphenyl alpha-beta double bond of stilbenes that had an oxygen functional group at the 4' carbon atom (e.g., resveratrol, piceatannol, and rhaponticin) to the corresponding aldehyde products. Carotenoids and apocarotenoids were not substrates for these enzymes. The two homologous enzymes from Bradyrhizobium sp. did not possess carotenoid or stilbene cleavage oxygenase activities, but showed activity with farnesol. To investigate whether the oxidative cleavage of stilbenes proceeds via a monooxygenase or dioxygenase reaction, oxygen-labeling studies were conducted with NOV2. Our labeling studies show that the double-bond cleavage of stilbenes occurs via a monooxygenase reaction mechanism.

The Carotenase AtCCD1 from Arabidopsis thaliana Is a Dioxygenase

Apocarotenoids resulting from the oxidative cleavage of carotenoids serve as important signaling and accessory molecules in a variety of biological processes. The enzymes catalyzing these reactions are referred to as carotenases or carotenoid oxygenases. Whether they act according to a monooxygenase mechanism, requiring two oxygens from different sources, or a dioxygenase mechanism is still a topic of controversy. In this study, we utilized the readily available beta-apo-8'-carotenal as a substrate for the heterologously expressed AtCCD1 protein from Arabidopsis thaliana to investigate the oxidative cleavage mechanism of the 9,10 double bond of carotenoids. Beta-ionone and a C(17)-dialdehyde were detected as products by gas and liquid chromatography-mass spectrometry as well as NMR analysis. Labeling experiments using H(2)(18)O or (18) O(2) showed that the oxygen in the keto-group of beta-ionone is derived solely from molecular dioxygen. When experiments were performed in an (18)O(2)-enriched atmosphere, a substantial fraction of the C(17)-dialdehyde contained labeled oxygen. The results unambiguously demonstrate a dioxygenase mechanism for the carotenase AtCCD1 from A. thaliana.

Characterization of a DNA-Cleaving deoxyribozyme

A copper-dependent self-cleaving DNA that was isolated by in vitro selection has been minimized to its smallest active domain using both in vitro selection and rational design methods. The minimized 46-nucleotide deoxyribozyme forms duplex and triplex substructures that flank a highly conserved catalytic core. This self-cleaving construct can be converted into a bimolecular complex that comprises separate substrate and enzyme domains. Substrate cleavage is directed at one of two adjacent nucleotides and proceeds via an oxidative cleavage mechanism that is unique to the position cleaved. The structural, kinetic and mechanistic characteristics of this DNA-cleaving deoxyribozyme are reported.

A new one-step method for oxaadamantane synthesis

Oxidation of 2-methyl-2-hydroxyadamantane by trifluoroperacetic acid in trifluoroacetic acid gives oxaadamantane and exo-2-oxaadamantane-4-ol in a good yield. Other 2-hydroxyadamantane derivatives do not undergo this transformation. An oxidative cleavage and subsequent cyclization mechanism is proposed.

Novel Mechanism for Oxidative Cleavage of Glycosidic Bonds: Evidence for an Oxygen Dependent Reaction

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTNovel Mechanism for Oxidative Cleavage of Glycosidic Bonds: Evidence for an Oxygen Dependent ReactionJian-Fang Cui, Styrbjoern Bystroem, Peter Eneroth, and Ingemar BjoerkhemCite this: J. Org. Chem. 1994, 59, 26, 8251–8255Publication Date (Print):December 1, 1994Publication History Published online1 May 2002Published inissue 1 December 1994https://doi.org/10.1021/jo00105a050RIGHTS & PERMISSIONSArticle Views377Altmetric-Citations20LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (527 KB) Get e-Alerts Get e-Alerts

19] Neoglycolipids: Probes in structure /function assignments to oligosaccharides

This chapter reviews the recent structure/function assignments made bythe neoglycolipid technology. Analysis by liquid secondary ion mass spectrometry (LSIMS) of neoglycolipids derived from O-glycosidic oligosaccharides has proved to be a powerful sequencing approach. The chapter discusses the results of the application of the neoglycolipid technology to analyze the core and backbone domains of O-glycosidic oligosaccharides released by alkaline borohydride degradation from mucin-type glycoproteins. As the reduced oligosaccharides contain no reactive aldehydes, mild periodate oxidation conditions are used such that overoxidation does not occur and a reactive aldehyde is generated at the reduced end. The mechanism of oxidative cleavage under the mild periodate conditions used is analyzed by LSIMS. Cleavage occurs specifically at the threo-diol C-4-C-5 bond of the core N-acetylgalactosaminitol, giving rise to two cleavage products with differing molecular masses. Although this cleavage would be a drawback in carbohydrate-recognition systems that require the intact core monosaccharide, it does have the advantage of allowing unambiguous assignment by LSIMS of positions of linkage of oligosaccharide sequences to the core N-acetylgalactosamine.

Oxidative polypeptide cleavage mediated by EDTA-Fe covalently linked to cysteine residues.

Chemical cleavage with reactive oxygen species generated by EPD-Fe, a protein-tethered EDTA-Fe reagent, has been proposed as a method to map the structure of nonnative equilibrium protein folding intermediates [Ermácora, M. R., Delfino, J. M., Cuenoud, B., Schepartz, A., & Fox, R. O. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 6383-6387]. The chemical structure of protein cleavage products and the mechanism of backbone scission for this class of reagents have been unclear. Here, we report the nature of EPD-Fe-mediated backbone cleavage of a small model peptide. The EPD-Fe reagent was attached to a partially alpha-helical peptide, alpha 1BA1a (Ac-AEAEEAAKKAKEACKA-NH2), through a mixed disulfide. Backbone cleavage was initiated by addition of the iron reductant ascorbate. Chemical analysis of the novel cleavage products revealed an oxidative cleavage mechanism, probably initiated by diffusible hydroxyl radicals. The EPD-Fe-mediated cleavage technique appears to be suitable for the analysis of nonnative protein states such as the molten globule.

Kinetics and mechanism of oxidative cleavage of the metal-metal bond in [M 2(CO) 10] 2−, MCr, Mo and W

Electrochemically-induced metal-metal bond cleavage in [M 2(CO) 10] 2− (MCr, Mo, W) has been studied using cyclic voltammetry, bulk electrolysis and double potential step chronocoulometry. Metal-metal bond homolysis, which occurs on oxidation in THF, can be modeled with an EC second-order disproportionation mechanism. The key step involves reaction of 2[M 2(CO) 10] ·− to form [M 2(CO) 10] 2− and M(CO) 5(THF). Electron transfer rate constants for the homogeneous disproportionation step, k d, were determined by double potential step chronocoulometry: 2.5 ± 0.1 × 10 3 M −1 s −1 for [W 2(CO) 10] ·− and 5.9 ± 0.3 × 10 2 M −1 s −1 for [Mo 2(CO) 10] ·− in THF at 20.0 °C. The [Cr 2(CO) 10] ·− radical underwent disproportionation too slowly to observe at room temperature, but a value of k d ⩽ 1.7 × 10 2 M −1 s −1 was estimated to be the upper limit of the rate constant at 35.0 °C. Activation parameters for k d were determined. For [Mo 2(CO) 10] ·−, Δ H ‡=6.9 ± 0.5 kcal mol −1 and Δ S ‡=−22.4 ± 1.9 cal K −1 mol −1. For [W 2(CO) 10] ·−, Δ H ‡=3.3 ± 0.5 kcal mol −1 and Δ S ‡=−31.7 ± 0.5 cal K −1 mol −1. The relative reactivities of the radicals W > Mo ⪢ Cr parallel the driving force for electron transfer, as measured by the potential difference for the oxidation of [M 2(CO) 10] 2− and [M 2(CO) 10] ·−. The k d step is proposed to involve outer-sphere electron transfer.

ChemInform Abstract: Alkene Oxidation Catalyzed by a Ruthenium‐Substituted Heteropolyanion, SiRu(L)W11O39: The Mechanism of the Periodate Mediated Oxidative Cleavage.

AbstractThe heteropolyanion mentioned in the title is synthesized and characterized.

A novel mechanism for oxidative cleavage of prolyl peptides induced by the hydroxyl radical

Mechanism for the oxidative cleavage of proline-containing peptides induced by the hydroxyl radical ( •OH) has been studied. Accompanying the oxidation of prolyl peptides, we discovered the formation of significant amounts of γ-aminobutyric acid (GABA) in the acid hydrolysates of the oxidized peptides. GABA was assumed to be derived from the 2-pyrrolidone compound and, in addition, its generation led to the assumption that prolyl peptides were mainly cleaved at the proline residues by •OH, accompanied by the oxidative modification of proline by itself. Hence, in order to confirm this prediction, we undertook the reaction of proline with •OH using proline analogue (Z-proline) and isolated the 2-pyrrolidone compound as the major product. We proposed a novel mechanism for formation of the 2-pyrrolidone compound induced by •OH, which has been established for the first time in the oxidative cleavage of prolyl peptides.

Redox cycling of bleomycin-Fe(III) by an NADH-dependent enzyme, and DNA damage in isolated rat liver nuclei

Isolated rat liver nuclei were incubated aerobically with bleomycin (BLM) and FeCl 3 in the presence of NADH. An increase in NADH and oxygen consumption was observed accompanied by DNA cleavage as shown by gel electrophoresis. Malondialdehyde (MDA) was also formed, which partly derived from DNA indicating an oxidative cleavage mechanism. BLM and NADH were obligatory to provide these effects, whereas FeCl 3 could be omitted, without a complete loss of the activities mentioned above. This was explained by the presence of some iron in the nuclei. NADPH was consumed to a lesser extent compared to NADH and was less effective with respect to O 2 consumption and MDA formation. It could be excluded that mitochondrial or microsomal contaminations in nuclear preparations were responsible for the effects observed. The results suggest that the BLM-Fe(III)-complex can be repeatedly reduced (redox cycled) by NADH- (and NADPH-) dependent reductases of liver nuclei to BLM-Fe(II) which is known to form reactive oxygen species and to damage DNA. It is concluded that the enzymatic reduction of a BLM-metal complex in the cell nucleus may be an essential step in the cytotoxic activity of bleomycin.

The biosynthesis of patulin: The mechanism of oxidative aromatic ring cleavage and loss of side chain protons from aromatic intermediates.

Method to detect the incorporation of 18O and 2H by isotope shift in 13C-NMR spectroscopy was applied to study the mechanism of patulin biosynthesis in Penicillium patulum NRRL 2159A. From the results of incorporation experiments with 18O2 and [1- 13C, 18O2]-acetate, monooxygenase appeared to be involved in the ring cleavage of an aromatic intermediate. 2H from [2-13C, 2-2H3]-acetate was detected at C-5, but not at C-1, indicating that the side chain protons of the aromatic intermediate were lost in the course of patulin biosynthesis.

Mechanism of oxidative cleavage of organocobalt(III) macrocycles. Application of electrochemical techniques to irreversible electron-transfer processes

Mechanism of oxidative cleavage of organocobalt(III) macrocycles. Application of electrochemical techniques to irreversible electron-transfer processes

Mechanism of oxidative cleavage of .alpha.-hydroxyalkylchromium complexes

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMechanism of oxidative cleavage of .alpha.-hydroxyalkylchromium complexesJames H. Espenson and Andreja BakacCite this: J. Am. Chem. Soc. 1980, 102, 7, 2488–2489Publication Date (Print):March 1, 1980Publication History Published online1 May 2002Published inissue 1 March 1980https://doi.org/10.1021/ja00527a073RIGHTS & PERMISSIONSArticle Views30Altmetric-Citations10LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

Metal hydrides as electron donors. The mechanism of oxidative cleavage with tris(phenanthroline) complexes of iron(III)

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMetal hydrides as electron donors. The mechanism of oxidative cleavage with tris(phenanthroline) complexes of iron(III)C. L. Wong, R. J. Klingler, and J. K. KochiCite this: Inorg. Chem. 1980, 19, 2, 423–430Publication Date (Print):February 1, 1980Publication History Published online1 May 2002Published inissue 1 February 1980https://doi.org/10.1021/ic50204a028RIGHTS & PERMISSIONSArticle Views154Altmetric-Citations9LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

Direct alkyl chain cleavage after C-hydroxylation of dialkylnitrosamines in rats. A new pathway of the oxidative biotransformation.

Comparative in vivo investigations on the biotransformation of di-n-butylnitrosamine (DBNA) and (2-hydroxybutyl)-n-butylnitrosamine (HBBNA) showed the known omega-oxidation. However, a new metabolic mechanism of direct oxidative alkyl chain cleavage in the vicinity of the hydroxy group of HBBNA could be demonstrated.