- Azobispyrazole Family as Photoswitches Combining (Near-) Quantitative Bidirectional Isomerization and Widely Tunable Thermal Half-Lives from Hours to Years**
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Azobenzenes are classical molecular photoswitches that have been widely used. In recent endeavors of molecular design, replacing one or both phenyl rings with heteroaromatic rings has emerged as a strategy to expand molecular diversity and access improved photoswitching properties. Many mono-heteroaryl azo molecules with unique structures and/or properties have been developed, but the potential of bis-heteroaryl architectures is far from fully exploited. We report a family of azobispyrazoles, which combine (near-)quantitative bidirectional photoconversion and widely tunable Z-isomer thermal half-lives from hours to years. The two five-membered rings remarkably weaken the intramolecular steric hindrance, providing new possibilities for engineering the geometric and electronic structure of azo photoswitches. Azobispyrazoles generally exhibit twisted Z-isomers that facilitate complete Z→E photoisomerization, and their thermal stability can be broadly adjusted regardless of the twisted shape, overcoming the conflict between photoconversion (favored by the twisted shape) and Z-isomer stability (favored by the orthogonal shape) encountered by mono-heteroaryl azo switches.
- He, Yixin,Li, Tao,Shangguan, Zhichun,Xie, Mingchen,Yu, Chunyang,Zhang, Zhao-Yang
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- Generation of Fluorescent Adducts of Malondialdehyde and Amino Acids: Toward an Understanding of Lipofuscin
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Lipofuscin is a yellow-brown, highly fluorescent pigment that undergoes an age-related progressive accumulation in animal cells, mainly in postmitotic cells. It is a heterogeneous, high-molecular weight material associated with proteins, lipids and nucleic acids. Lipofuscin is implicated in many aspects of human health, including aging, oxidative stress, macular degeneration, lipid peroxidation, atherosclerosis, dementia (Alzheimer's Disease) and diseases associated with prions. Although the fluorescent properties of lipofuscin have long been recognized, neither histologists nor chemists have yet isolated the pigments themselves or characterized their optical properties. We have prepared lipofuscinlike species by reacting malondialdehyde (MDA) with cysteine (Cys). MDA: Cys adducts 3:2 and 2:2 are two of those that have been identified among the many that were present in the reaction. Whereas previous attempts to synthesize lipofuscinlike species resulted in compounds that were either nonfluorescent or emitted principally in the blue, the MDA:Cys adducts reported in this study are not only fluorescent but also emit over a broader range.
- Chowdhury, Pramit K.,Haider, Mintu,Choudhury, Prabir K.,Kraus, George A.,Desai, Meera J.,Armstrong, Daniel W.,Casey, Thomas A.,Rasmussen, Mark A.,Petrich, Jacob W.
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- Synthesis, structural studies and stability of model cysteine containing DNA-protein cross-links
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DNA-protein cross-links (DPCs) are bulky, helix-distorting lesions that are formed upon irreversible bonding of proteins to chromosomal DNA in the presence of cross-linking agents. Among a broad range of such agents are α,β-unsaturated carbonyl compounds, which act essentially as bifunctional alkylating agents and form adducts with DNA bases. These adducts can further undergo interactions with other cellular macromolecules leading to the formation of cross-linked products. We synthesized and structurally characterized N-acetylcysteine cross-links formed in the reactions with aldehydic adducts of adenine nucleosides, which possess enol functionality and represent model α,β-unsaturated carbonyl systems. Studies performed by the use of NMR spectroscopy, DFT and ab initio methods established that two of these cross-links exist as rotamers stable at room temperature. Application of Atoms in Molecules Theory enabled hydrogen bonding and other stabilizing interactions within the studied molecules to be estimated. Under physiological conditions the cross-links were found to be relatively stable until Nα-acetyllysine was present in the reaction medium. The presence of this amino acid caused fast transformation of the N-acetylcysteine cross-links into a range of their lysine derivatives. Although instability of the cysteine adduct with acrolein was reported, we showed that the mechanism involved in the gradual decomposition of the N-acetylcysteine cross-links differs from that proposed for acrolein adduct degradation. This demonstrates that in spite of similarities in their structures, numerous α,β-unsaturated carbonyl compounds can interact with nucleophilic biomolecules by different mechanisms leading to structural heterogeneity of the resulting products. Our findings provide an explanation for difficulties in identifying the cysteine containing DPCs in vivo and in vitro, and may be of great importance with respect to detection and isolation of such lesions from biological materials.
- Salus, Kinga,Hoffmann, Marcin,Siod?a, Tomasz,Wyrzykiewicz, Bo?ena,Pluskota-Karwatka, Donata
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- Structural studies of malonaldehyde-glyoxal and malonaldehyde-methylglyoxal etheno adducts of adenine nucleosides based on spectroscopic methods and DFT-GIAO calculations
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Etheno adducts are formed in the reactions of DNA bases with chloroacetaldehyde, with lipid peroxidation products, and also with metabolites of vinyl chloride and furan. The presence of such modifications in the genetic material may lead to errors in replication with consequences of mutations and even carcinogenesis. For an understanding of the biological significance of etheno adducts it is important to determine their structures. Structural identification is also essential for using these adducts as inflammatory or cancer biomarkers. This paper reports structural studies on two adducts formed in the reactions of malonaldehyde and glyoxal with adenosine (M1Gx-A), and malonaldehyde and methylglyoxal with 2′-deoxyadenosine (M1MGx-dA). NMR spectroscopy and theoretical methods have been used. DFT-GIAO calculations were performed at M06/6-311++G(2df,2pd), B3LYP/6-311++G(2df,2pd) and M06/6-31++G(d,p) levels both in the gas phase and taking into account the effect of solvents (water, methanol and DMSO) using PCM approximation. It has been shown that when M06 or B3LYP functionals with the 6-311++G(2df,2pd) basis set are used, 1H NMR chemical shifts very close to experimental values are obtained and that the results of GIAO calculations at the M06/6-31++G(d,p) level have a better correlation with measured 13C NMR chemical shift values. PCM improves the correlation of results in both cases.
- Salus, Kinga,Hoffmann, Marcin,Wyrzykiewicz, Bozena,Pluskota-Karwatka, Donata
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- Antiradical and antioxidant activity of phenylhydrazones of aromatic aldehydes
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With the aim of searching for new antioxidants, including those of the biogenic type, the antioxidant properties of phenylhydrazones of some aromatic aldehydes were studied under conditions of ascorbate-dependent peroxide oxidation of oleic acid residues
- Pleskushkina,Nikolaevskii,Filippenko
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- Modification of casein by the lipid oxidation product malondialdehyde
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The reaction of malondialdehyde with casein was studied in aqueous solution to evaluate the impact of this lipid oxidation product on food protein modification. By using multiresponse modeling, a kinetic model was developed for this reaction. The influence of temperature and pH on protein browning and malondialdehyde degradation was evaluated. The hypothesis that one malondialdehyde unit leads to the cross-linking of two casein-bound lysine residues was in accordance with the data. At higher malondialdehyde concentrations, a different reaction mechanism was operative, probably involving a dihydropyridine cross-link. The results obtained were compared with the reaction of casein with 2-oxopropanal, a well-studied α-dicarbonyl compound. The reaction of casein with 2-oxopropanal followed a different reaction pathway. Comparison of the degree of browning of casein by reaction with malondialdehyde and 2-oxopropanal showed a considerably higher degree of browning induced by malondialdehyde. This research has shown that kinetic modeling is a useful tool to unravel reaction mechanisms. Clearly, the contribution of lipid oxidation products, such as malondialdehyde, to protein modification (both in food and in vivo) can be substantial and needs to be taken into account in future studies.
- Adams, An,De Kimpe, Norbert,Van Boekel, Martinus A. J. S.
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- A novel fluorescent malondialdehyde-lysine adduct
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We report a novel type of fluorescent product derived from the reaction of the lysine residue with malondialdehyde (MDA). When the lysine-containing peptide (N-acetyl-glycyl-L-lysine methyl ester) was treated with MDA prepared by the acid hydrolysis of 1,1,3,3-tetramethoxypropane, the main fluorescent product, which corresponded neither to the 1-amino-3-iminopropene derivative (2) nor to the 4-methyl-1,4-dihydro-3,5-dicarbaldehyde derivative (3), was detected by reverse-phase HPLC. By analysis of its UV NMR, and high-resolution FAB mass spectra, it was confirmed to be 1-[5-carboxymethyl-5-(N-acetylglycylamino)pentyl]-3-[1-5-carboxymethyl-5 -acetylglycylamino)-pentyl)-3,5-diformyl-1,4-dihydropyridin-4-yl] pyridinium (1). This finding may provide a new clue to the formation mechanisms of fluorescent lipofuscin-like pigment.
- Itakura, Koichi,Uchida, Koji,Osawa, Toshihiko
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- Identification of fluorescent 2′-deoxyadenosine adducts formed in reactions of conjugates of malonaldehyde and acetaldehyde, and of malonaldehyde and formaldehyde
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2′-Deoxyadenosine was reacted with malonaldehyde in the presence of formaldehyde or acetaldehyde. The reactions were carried out at 37 °C in aqueous solution at acidic conditions. The reaction mixtures were analyzed by HPLC. In both reactions, two major products were formed. The reaction products were isolated and purified by C18 chromatography, and their structures were characterized by UV absorbance, fluorescence emission, 1H and 13C NMR spectroscopy, and mass spectrometry. The reaction products isolated from the mixture containing formaldehyde, malonaldchyde, and deoxyadenosine were identified as 3-(2′-deoxy-β-D-ribofuranosyl)-7H-8-formyl[2,1-i]pyrimidopurine (M1FA-dA) and 9-(2′-deoxy-β-D-ribofuranosyl)-6-(3,5-diformyl-l,4-dihydro-1-pyrid yl)purine (M2FA-dA). In the reaction mixture consisting of acetaldehyde, malonaldehyde, and deoxyadenosine, the identities of the products were determined to be 3-(2′-deoxy-β-D-ribofuranosyl)-7-methyl-8-formyl[2,1-i]pyrimidopur ine (M1-AA-dA) and 9-(2′-deoxy-β-D-ribofuranosyl)-6-(3,5-diformyl-4-methyl-1,4-dihydr o-1-pyridyl)purine (M2AA-dA). The yields of the compounds were 1.8 and 0.7% for M1FA-dA and M2FA-dA, respectively, and 6.8 and 10% for M1AA-dA and M2AA-dA, respectively. All compounds exhibited marked fluorescent properties. These findings show that in addition to direct reaction of a specific aldehyde with 2′-deoxyadenosine, aldehyde conjugates also may react with the base. Although three of the adducts (M1FA-dA, M2FA-dA, and M1AA-dA) could not be detected in reactions carried out under neutral conditions, the possibility that trace amounts of the adducts may be formed under physiological conditions cannot be ruled out. Therefore, conjugate adducts must be considered in work that aims at clarifying the mechanism of aldehyde genotoxicity.
- Curieux, Frank Le,Pluskota, Donata,Munter, Tony,Sjoeholm, Rainer,Kronberg, Leif
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- Divalent and oxabridged neonicotinoids constructed by dialdehydes and nitromethylene analogues of imidacloprid: Design, synthesis, crystal structure, and insecticidal activities
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A series of divalent and oxabridged neonicotinoids were synthesized by reactions of nitromethylene analogues of imidacloprid and dialdehydes, and their structures were confirmed by 1H NMR, 13C NMR, high-resolution mass spectroscopy, and X-ray diffraction analysis. The bioassays indicated that some of them were endowed with excellent insecticidal activities against cowpea aphid (Aphis craccivora), armyworm (Pseudaletia separata Walker), and brown planthopper (Nllaparvata lugens). Divalent neonicotinoid 6 and oxabridged 8a had higher activities than imidacloprid against cowpea aphids and armyworm; furthermore, the activity of 8a was 40.4-fold higher than that of imidacloprid against imidacloprid-resistant brown planthopper.
- Shao, Xusheng,Hua,Xiaoyong,Xinglei,Zewen,Zhong,Qian, Xuhong
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- Development of a selective ESI-MS derivatization reagent: Synthesis and optimization for the analysis of aldehydes in biological mixtures
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In LC-MS, derivatization is primarily used to improve ionization characteristics, especially for analytes that are not (efficiently) ionized by ESI or APCI such as aldehydes, sugars, and steroids. Derivatization strategies are then directed at the incorporation of a group with a permanent charge. A compound class that typically requires derivatization prior to LC-MS is the group of small aliphatic aldehydes that are, for instance, analyzed as the key biomarkers for lipid peroxidation in organisms. Here we report the development of a new tailor-made, highly sensitive, and selective derivatization agent 4-(2-(trimethylammonio)ethoxy)benzenaminium halide (4-APC) for the quantification of aldehydes in biological matrixes with positive ESI-MS/MS without additional extraction procedures. 4-APC possesses an aniline moiety for a fast selective reaction with aliphatic aldehydes as well as a quaternary ammonium group for improved MS sensitivity. The derivatization reaction is a convenient one-pot reaction at a mild pH (5.7) and temperature (10°C). As a result, an in-vial derivatization can be performed before analysis with an LC-MS/MS system. All aldehydes are derivatized within 30 min to a plateau, except malondialdehyde, which requires 300 min to reach a plateau. All derivatized aldehydes are stable for at least 35 h. Linearity was established between 10 and 500 nM and the limits of detection were in the 3-33 nM range for the aldehyde derivatives. Furthermore, the chosen design of these structures allows tandem MS to be used to monitor the typical losses of 59 and 87 from aldehyde derivatives, thereby enabling screening for aldehydes. Finally, of all aldehydes, pentanal and hexanal were detected at elevated levels in pooled healthy human urine samples.
- Eggink, Mark,Wijtmans, Maikel,Ekkebus, Reggy,Lingeman, Henk,De Esch, Iwan J. P.,Kool, Jeroen,Niessen, Wilfried M. A.,Irth, Hubertus
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- Reaction of Malonaldehyde with Adenosine. Formation of a Novel Adduct Containing a Dioxazatricycloundecene Residue in the Base-pairing Region
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Reaction of malonaldehyde with adenosine at pH 4.5 gave three major adducts including a novel one containing diastereomeric dioxazatricycloundecene residue, formed by addition of three malonaldehyde units.
- Seto, Hiroshi,Seto, Takako,Nagakura, Koichi,Koike, Hiroshi
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- A purified MAA-based ELISA is a useful tool for determining anti-MAA antibody titer with high sensitivity
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Atherosclerosis is widely accepted to be a chronic inflammatory disease, and the immunological response to the accumulation of LDL is believed to play a critical role in the development of this disease. 1,4-Dihydropyridine-type MAA-adducted LDL has been implicated in atherosclerosis. Here, we have demonstrated that pure MAA-modified residues can be chemically conjugated to large proteins without by-product contamination. Using this pure antigen, we established a purified MAA-ELISA, with which a marked increase in anti-MAA antibody titer was determined at a very early stage of atherosclerosis in 3-month ApoE-/-mice fed with a normal diet. Our methods of N? -MAA-L-lysine purification and purified antigen-based ELISA will be easily applicable for biomarker-based detection of early stage atherosclerosis in patients, as well as for the development of an adduct-specific Liquid Chromatography/Mass Spectrometry-based quantification of physiological and pathological levels of MAA.
- Shimomoto, Takasumi,Collins, Leonard B.,Yi, Xianwen,Holley, Darcy W.,Zhang, Zhenfa,Tian, Xu,Uchida, Koji,Wang, Chunguang,H?rkk?, Sohvi,Willis, Monte S.,Gold, Avram,Bultman, Scott J.,Nakamura, Jun
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- Contribution of lipid dynamics on the inhibition of bovine brain synaptosomal Na+-K+-ATPase activity induced by 4-hydroxy-2-nonenal
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The effects of lipid hydroperoxide degradation products, such as 4-hydroxy-2-nonenal (HNE) and malondialdehyde (MDA), on bovine brain synaptosomal ATPase activities and their membrane lipid organization were examined. When the synaptosomes were treated with HNE, this resulted in the decrease of Na+-K+-ATPase activity with the loss of sulfhydryl (SH) groups in the membrane proteins. In contrast, MDA treatment of the synaptosomes did not induce an appreciable decrease in the ATPase activity or a loss of SH groups. The decreases in ATPase activity and SH content by treatment with HNE were also observed, as a Na+-K+-ATPase preparation was used in place of the synaptosomes. On the other hand, HNE had very little effect on synaptosomal Ca2+- and Mg2+-ATPase activities. The results of the kinetic analysis of the Na+-K +-ATPase activity indicated that the decrease in the activity by HNE-modification is due to a decreased affinity for the substrate. ATP completely protected the ATPase from the HNE attack. Modification of the synaptosomes with HNE caused a decrease in the membrane lipid fluidity near the lipid/water interface, not the lipid layer interior. In addition, it was found that there is a good relationship between the lipid fluidity and the Na +-K+-ATPase activity under the presence of various concentrations of HNE, suggesting that the lipid dynamics are closely related to HNE-induced inhibition of the ATPase activity. On the other hand, MDA did not induce change in the membrane lipid fluidity. HNE and MDA are mainly incorporated into the lipid and protein fractions in the synaptosomal membranes, respectively. Based on these results, we proposed a possible mechanism of HNE-induced inhibition of synaptosomal Na+-K+-ATPase activity associated with alterations in the membrane lipid organization.
- Kadoya, Akinori,Miyake, Hiromi,Ohyashiki, Takao
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- 2-methyl nicotinate as well as preparation method and application thereof
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The invention relates to 2-methyl nicotinate as well as a preparation method and application thereof. The preparation method comprises the following steps: (1) reacting 1, 1, 3, 3-tetramethoxypropane or 1, 1, 3, 3-tetraethoxypropane under the action of acid to obtain a compound B; (2) reacting the compound B and beta-aminocrotonate in a first organic solvent to obtain 2-methyl nicotinate, wherein no foul acrolein is used in the process, the safety coefficient of production is effectively improved, the reaction raw materials are easy to obtain, the conditions are mild, the operation is simple, the yield is greater than 65%, the product purity reaches 98% or above, and the method is suitable for industrial production and has a wide application prospect. The obtained product can be used as an intermediate for synthesizing 2-methyl nicotinic acid, and can be used for synthesizing medicines.
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Paragraph 0114-0119; 0125-0130; 0137-0142
(2021/05/22)
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- Cu2+ selective chelators relieve copper-induced oxidative stress: In vivo
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Copper ions are essential for biological function yet are severely detrimental when present in excess. At the molecular level, copper ions catalyze the production of hydroxyl radicals that can irreversibly alter essential bio-molecules. Hence, selective copper chelators that can remove excess copper ions and alleviate oxidative stress will help assuage copper-overload diseases. However, most currently available chelators are non-specific leading to multiple undesirable side-effects. The challenge is to build chelators that can bind to copper ions with high affinity but leave the levels of essential metal ions unaltered. Here we report the design and development of redox-state selective Cu ion chelators that have 108 times higher conditional stability constants toward Cu2+ compared to both Cu+ and other biologically relevant metal ions. This unique selectivity allows the specific removal of Cu2+ ions that would be available only under pathophysiological metal overload and oxidative stress conditions and provides access to effective removal of the aberrant redox-cycling Cu ion pool without affecting the essential non-redox cycling Cu+ labile pool. We have shown that the chelators provide distinct protection against copper-induced oxidative stress in vitro and in live cells via selective Cu2+ ion chelation. Notably, the chelators afford significant reduction in Cu-induced oxidative damage in Atp7a-/- Menkes disease model cells that have endogenously high levels of Cu ions. Finally, in vivo testing of our chelators in a live zebrafish larval model demonstrate their protective properties against copper-induced oxidative stress.
- Rakshit, Ananya,Khatua, Kaustav,Shanbhag, Vinit,Comba, Peter,Datta, Ankona
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p. 7916 - 7930
(2018/11/03)
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- Preparation method of 3-thiophenecarboxaldehyde
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The invention relates to the technical field of organic synthesis, in particular to a preparation method of 3-thiophenecarboxaldehyde. The preparation method of 3-thiophenecarboxaldehyde comprises thefollowing steps: performing reaction on 1,1,3,3-tetramethoxypropane under the acidic condition, performing mixed reaction on the reaction product and 1,4-dithio-2,5-diol under the alkaline conditionand performing aftertreatment to obtain the 3-thiophenecarboxaldehyde. By the preparation method of 3-thiophenecarboxaldehyde, the 3-thiophenecarboxaldehyde product with the purity exceeding 98 percent can be prepared only through simple mixing and stirring reaction, reaction does not need ultralow temperature and dangerous reagents in the preparation process, and the production safety coefficientis increased. Furthermore, the preparation method provided by the invention is simple in operation, the raw materials are easily available, operation cost and raw material cost are reduced, and the preparation method is suitable for industrialized production of 3-thiophenecarboxaldehyde.
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Page/Page column 6-8
(2018/06/15)
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- Antioxidant activity of oleuropein and semisynthetic acetyl-derivatives determined by measuring malondialdehyde in rat brain
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Objectives: The purpose of this study was the evaluation of the antioxidant activity of natural and semisynthetic polyphenol derivatives from Olea europea L., by assessing malondialdehyde (MDA), an important marker of oxidative stress. Methods: Polyphenol as hydroxytyrosol, oleuropein, oleuropein aglycone as mix of four tautomeric forms and their respective acetyl-derivatives were obtained from olive leaves using semisynthetic protocols. These compounds were administered intraperitoneally to Wistar rats treated with paraquat, an herbicide which is able to cause oxidative stress after central administration. Malondialdehyde was derivatized with 2,4-dinitrophenylhydrazine to produce hydrazone that was purified by solid-phase extraction. Using high-performance liquid chromatography coupled with a diode array, free and total MDA was measured on homogenate rat brain as marker of lipid peroxidation. The analytical method was fully validated and showed linearity in the tested concentration range, with detection limit of 5 ng/ml. Recovery ranged from 94.1 to 105.8%. Key findings: Both natural and semisynthetic polyphenol derivatives from a natural source as olive leaves were able to reduce MDA detection. The more lipophilic acetyl-derivatives showed an antioxidant activity greater than parent compounds. This potency seems to put in evidence a strict correlation between lipophilicity and bioavailability.
- Rizzo, Milena,Ventrice, Domenica,Giannetto, Francesca,Cirinnà, Salvatore,Santagati, Natale Alfredo,Procopio, Antonio,Mollace, Vincenzo,Muscoli, Carolina
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p. 1502 - 1512
(2017/10/11)
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- A comparative study on the efficacy of different probes to predict the photo-activity of nano-titanium dioxide toward biomolecules
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TiO2 is a reactive material able to cause the degradation of organic molecules following activation by UV light. This reactivity may be useful, e.g. in environmental or medical applications, but undesired when TiO2 is used as a UV filter in cosmetics and composites since it reduces the photo-stability of the material, and represents a possible pathway of injury. Conventional methods to measure the photo-activity of TiO2 include the degradation of small molecules or dyes. However the suitability of these methods to predict the photo-activity of TiO2 in biological systems is uncertain. This is the first product of a study, conducted within the FP7 EU project SETNanoMetro, that has as a main goal the standardizations of protocols to assess the oxidative potential of TiO2 nanopowders in biofluids. Here, the ability of a series of nano-TiO2 powders exhibiting different crystalline phases to degrade rhodamine B, a dye commonly used in photo-catalysis, and two model biomolecules (linoleic acid and 2-deoxyribose) under simulated sunlight was compared. Electron paramagnetic resonance (EPR) spectroscopy associated to different spin-probes or spin-traps was used to elucidate the reactive species involved in the processes. The results show how the photo-efficiency of TiO2 is affected by the kind of probe and by the presence of species that adsorb at the surface of the nanoparticles underlining the need of appropriate standard operating procedures (SOP) to evaluate the oxidative damage potential of semiconducting nanomaterials.
- Marucco,Carella,Fenoglio
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p. 89559 - 89568
(2015/11/10)
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- Efficacy and site specificity of hydrogen abstraction from DNA 2-deoxyribose by carbonate radicals
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The carbonate radical anion CO3?- is a potent reactive oxygen species (ROS) produced in vivo through enzymatic one-electron oxidation of bicarbonate or, mostly, via the reaction of CO2 with peroxynitrite. Due to the vitally essential role of the carbon dioxide/bicarbonate buffer system in regulation of physiological pH, CO3?- is arguably one of the most important ROS in biological systems. So far, the studies of reactions of CO3?- with DNA have been focused on the pathways initiated by oxidation of guanines in DNA. In this study, low-molecular products of attack of CO3?- on the sugar-phosphate backbone in vitro were analyzed by reversed phase HPLC. The selectivity of damage in double-stranded DNA (dsDNA) was found to follow the same pattern C4′ > C1′ > C5′ for both CO3?- and the hydroxyl radical, though the relative contribution of the C1′ damage induced by CO3?- is substantially higher. In single-stranded DNA (ssDNA) oxidation at C1′ by CO3?- prevails over all other sugar damages. An approximately 2000-fold preference for 8-oxoguanine (8oxoG) formation over sugar damage found in our study identifies CO3?- primarily as a one-electron oxidant with fairly low reactivity toward the sugar-phosphate backbone.
- Roginskaya, Marina,Moore,Ampadu-Boateng,Razskazovskiy
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p. 1431 - 1437
(2015/11/09)
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- A rapid, sensitive and solvent-less method for determination of malonaldehyde in meat by stir bar sorptive extraction coupled thermal desorption and gas chromatography/mass spectrometry with in situ derivatization
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RATIONALE The traditional methods for analysis of malonaldehyde (MDA), such as the thiobarbituric acid (TBA) assay, require strong acidity at high temperature for derivatization and lack specificity in analysis. Stir bar sorptive extraction (SBSE) coupled with thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS) with in situ derivatization using pentafluorophenylhydrazine (PFPH) under mild conditions is an emerging technique for MDA analysis. METHODS MDA in meat was derivatized with PFPH at pH ~4 for 1 h at room temperature, forming a relative stable derivative of MDA-PFPH. The derivative of MDA-PFPH was simultaneously extracted using SBSE. Then, MDA-PFPH was thermally released and quantitatively analyzed by GC/MS in selected ion monitoring (SIM) mode. RESULTS The method of SBSE-TD-GC/MS for MDA analysis with in situ derivatization was optimized and validated with good linearity, specificity and limit of detection/quantification (LOD/LOQ). The method was successfully applied for analysis of MDA in raw and cooked meat (pork). CONCLUSIONS The SBSE-TD-GC/MS method was suitable to monitor and analyze MDA in meat samples at trace levels. The simple, sensitive and solvent-less method with moderated in situ derivatization can be applied for analysis of MDA in a wide variety of foods and biological samples.
- Ruan, Eric Dongliang,Aalhus, Jennifer,Juárez, Manuel
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p. 2723 - 2728
(2016/02/18)
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- Characterization of a new enzyme oxidizing ω-amino group of aminocarboxyric acid, aminoalcohols and amines from Phialemonium sp. AIU 274
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A new enzyme exhibiting oxidase activity for ω-aminocarboxylic acids, ω-aminoalcohols, monoamines and diamines was found from a newly isolated fungal strain, Phialemonium sp. AIU 274. The enzyme also oxidized aromatic amines, but not l- and d-amino acids. The Vmax/Km value for hexylamine was higher than those for 6-aminoalcohol and 6-aminhexanoic acid in the aliphatic C6 substrates. In the aliphatic amines, the higher Vmax/Km values were obtained by the longer carbon chain amines. Thus, the enzyme catalyzed oxidative deamination of the ω-amino group in a wide variety of the ω-amino compounds and preferred medium- and long-chain substrates. The oxidase with such broad substrate specificity was first reported here. The enzyme contained copper, and the enzyme activity was strongly inhibited by isoniazid, iproniazid and semicarbazide, but not by clorgyline and pargyline. The enzyme was composed of two identical subunits of 75 kDa.
- Isobe, Kimiyasu,Sasaki, Tomoko,Aigami, Yuusuke,Yamada, Miwa,Kishino, Shigenobu,Ogawa, Jun
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- 7,11-METHANOCYCLOOCTA [B] QUINOLINE DERIVATIVE AS HIGHLY FUNCTIONALIZABLE ACETYLCHOLINESTERASE INHIBITORS
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The present invention concerns new highly functionalizable Huprine derivatives of formula I: a method for preparing such compounds and their use for treating neurological diseases in which the level of acetylcholine is affected such as Alzheimer's disease.
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Page/Page column 27
(2011/10/31)
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- Lipid peroxyl radicals mediate tyrosine dimerization and nitration in membranes
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Protein tyrosine dimerization and nitration by biologically relevant oxidants usually depend on the intermediate formation of tyrosyl radical ( ·Tyr). In the case of tyrosine oxidation in proteins associated with hydrophobic biocompartments, the participation of unsaturated fatty acids in the process must be considered since they typically constitute preferential targets for the initial oxidative attack. Thus, we postulate that lipid-derived radicals mediate the one-electron oxidation of tyrosine to ·Tyr, which can afterward react with another ·Tyr or with nitrogen dioxide (·NO 2) to yield 3,3′-dityrosine or 3-nitrotyrosine within the hydrophobic structure, respectively. To test this hypothesis, we have studied tyrosine oxidation in saturated and unsaturated fatty acid-containing phosphatidylcholine (PC) liposomes with an incorporated hydrophobic tyrosine analogue BTBE (N-t-BOC l-tyrosine tert-butyl ester) and its relationship with lipid peroxidation promoted by three oxidation systems, namely, peroxynitrite, hemin, and 2,2′-azobis (2-amidinopropane) hydrochloride. In all cases, significant tyrosine (BTBE) oxidation was seen in unsaturated PC liposomes, in a way that was largely decreased at low oxygen concentrations. Tyrosine oxidation levels paralleled those of lipid peroxidation (i.e., malondialdehyde and lipid hydroperoxides), lipid-derived radicals and BTBE phenoxyl radicals were simultaneously detected by electron spin resonance spin trapping, supporting an association between the two processes. Indeed, α-tocopherol, a known reactant with lipid peroxyl radicals (LOO·), inhibited both tyrosine oxidation and lipid peroxidation induced by all three oxidation systems. Moreover, oxidant-stimulated liposomal oxygen consumption was dose dependently inhibited by BTBE but not by its phenylalanine analogue, BPBE (N-t-BOC l-phenylalanine tert-butyl ester), providing direct evidence for the reaction between LOO· and the phenol moiety in BTBE, with an estimated second-order rate constant of 4.8 - 103 M1 s-1. In summary, the data presented herein demonstrate that LOO · mediates tyrosine oxidation processes in hydrophobic biocompartments and provide a new mechanistic insight to understand protein oxidation and nitration in lipoproteins and biomembranes.
- Bartesaghi, Silvina,Wenzel, Jorge,Trujillo, Madia,Lopez, Marcos,Joseph, Joy,Kalyanaraman, Balaraman,Radi, Rafael
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p. 821 - 835
(2011/02/26)
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- Modifying apolipoprotein A-I by malondialdehyde, but not by an array of other reactive carbonyls, blocks cholesterol efflux by the ABCA1 pathway
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Dysfunctional high density lipoprotein (HDL) is implicated in the pathogenesis of cardiovascular disease, but the underlying pathways remain poorly understood. One potential mechanism involves covalent modification by reactive carbonyls of apolipoprotein A-I (apoA-I), the major HDL protein. We therefore determined whether carbonyls resulting from lipid peroxidation (malondialdehyde (MDA) and hydroxynonenal) or carbohydrate oxidation (glycolaldehyde, glyoxal, and methylglyoxal) covalently modify lipid-free apoA-I and inhibit its ability to promote cellular cholesterol efflux by the ABCA1 pathway. MDA markedly impaired the ABCA1 activity of apoA-I. In striking contrast, none of the other four carbonyls were effective. Liquid chromatography-electrospray ionization-tandem mass spectrometry of MDA-modified apoA-I revealed that Lys residues at specific sites had been modified. The chief adducts were MDA-Lys and a Lys-MDA-Lys cross-link. Lys residues in the C terminus of apoA-I were targeted for cross-linking in high yield, and this process may hinder the interaction of apoA-I with lipids and ABCA1, two key steps in reverse cholesterol transport. Moreover, levels of MDA-protein adducts were elevated in HDL isolated from human atherosclerotic lesions, suggesting that lipid peroxidation might render HDL dysfunctional in vivo. Taken together, our observations indicate that MDA damages apoA-I by a pathway that generates lysine adducts at specific sites on the protein. Such damage may facilitate the formation of macrophage foam cells by impairing cholesterol efflux by the ABCA1 pathway.
- Shao, Baohai,Pennathur, Subramaniam,Pagani, Ioanna,Oda, Michael N.,Witztum, Joseph L.,Oram, John F.,Heinecke, Jay W.
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experimental part
p. 18473 - 18484
(2011/04/17)
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- ROS-SENSITIVE IRON CHELATORS AND METHODS OF USING THE SAME
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The present invention provides compounds of Formula (I): along with compositions containing the same and methods of use thereof in treating oxidative stress.
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Page/Page column 9-10
(2010/02/16)
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- 2-Amino-5-aryl-pyridines as selective CB2 agonists: Synthesis and investigation of structure-activity relationships
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2-Amino-5-aryl-pyridines, exemplified by compound 1, had been identified as a synthetically tractable series of CB2 agonists from a high-throughput screen of the GlaxoSmithKline compound collection. Described herein are the results of an investigation of the structure-activity relationships (SAR) which led to the identification a number of potent and selective agonists.
- Gleave, Robert J.,Beswick, Paul J.,Brown, Andrew J.,Giblin, Gerard M.P.,Haslam, Carl P.,Livermore, David,Moses, Andrew,Nicholson, Neville H.,Page, Lee W.,Slingsby, Brian,Swarbrick, Martin E.
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scheme or table
p. 6578 - 6581
(2010/06/12)
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- A tandem MS precursor-ion scan approach to identify variable covalent modification of albumin Cys34: A new tool for studying vascular carbonylation
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We developed a liquid chromatography electrospray ionisation multi-stage mass spectrometry (LC-ESI-MS/MS) approach based on precursor-ion scanning and evaluated it to characterize the covalent modifications of Cys34 human serum albumin (HSA) caused by oxidative stress and reactive carbonyl species (RCS) adduction. HSA was isolated and digested enzymatically to generate a suitable-length peptide (LQQCPF) containing the modified tag residue. The resulting LQQCPF peptides were identified by LC-ESI-MS/MS in precursor-ion scan mode and further characterized in product-ion scan mode. The product ions for precursor-ion scanning were selected by studying the MS/MS fragmentation of a series of LQQCPF derivatives containing Cys34 modified with different α,β-unsaturated aldehydes and di and ketoaldehydes. We used a Boolean logic to enhance the specificity of the method: this reconstitutes a virtual current trace (vCT) showing the peaks in the three precursor-ion scans, marked by the same parent ion. The method was first evaluated to identify and characterize the Cys34 covalent adducts of HSA incubated with 4-hydroxy-hexenal, 4-hydroxy-trans-2-nonenal (HNE) and acrolein (ACR). Then we studied the Cys34 modification of human plasma incubated with mildly oxidized low-density lipoproteins (LDL), and the method easily identified the LQQCPF adducts with HNE and ACR. In other experiments, plasma was oxidized by 2,2′-azobis(2- amidinopropane) HCl (AAPH) or by Fe2+/H2O2. In both conditions, the sulfinic derivative of LQQCPF was identified and characterized, indicating that the method is suitable not only for studying RCS-modified albumin, but also to check the oxidative state of Cys34 as a marker of oxidative damage. Copyright
- Aldini, Giancarlo,Regazzoni, Luca,Orioli, Marica,Rimoldi, Isabella,Facino, Roberto Maffei,Carini, Marina
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experimental part
p. 1470 - 1481
(2009/10/10)
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- Amphiphilic/bipolar metallocorroles that catalyze the decomposition of reactive oxygen and nitrogen species, rescue lipoproteins from oxidative damage,and attenuate atherosclerosis in mice
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(Chemical Equation Presented) Antioxidans that work! The iron corrole 1-Fe (see picture) is a potetnt catalyst for decomposition of reactive oxygen and nitrogen species that binds selectively to lipoproteins. The complex also affects cholesterol levels and its cellular efflux. 1-Fe is more effective that natural antioxidants in reducing atherosclerosis development in mice. LDL = low-density lipoprotein.
- Haber, Adi,Mahammed, Atif,Fuhrman, Bianca,Volkova, Nina,Coleman, Raymond,Hayek, Tony,Aviram, Michael,Gross, Zeev
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supporting information; experimental part
p. 7896 - 7900
(2009/05/07)
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- Extreme rate acceleration by axial thiolate coordination on the isomerization of endoperoxide catalyzed by iron porphyrin
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(Chemical Equation Presented) A coordinated effort: The isomerization mechanism of prostaglandin H2 (PGH2), which is catalytically isomerized to prostacyclin or thromboxane A2 by cytochrome P450s, was investigated using a hemethiolate complex and an endoperoxide. Isomerization of endoperoxides proceeded very rapidly with this complex, whereas imidazole- or chloride-ligated heme had slight or no catalytic activity (see scheme).
- Yamane, Takehiro,Makino, Kohei,Umezawa, Naoki,Kato, Nobuki,Higuchi, Tsunehiko
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supporting information; experimental part
p. 6438 - 6440
(2009/03/11)
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- Zeolite-supported chromium(VI) oxide: A mild, efficient, and inexpensive reagent for oxidative deprotection of trimethylsilyl ethers under microwave irradiation
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Primary and secondary trimethylsilyl ethers are efficiently converted, to the corresponding carbonyl compounds using HZSM-5 zeolite-supported CrO 3 under microwave irradiation in solventless system.
- Heravi, Majid M.,Hydarzadeh, Fereshteh,Farhangi, Yahya,Ghassemzadeh, Mitra
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p. 1473 - 1475
(2007/10/03)
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- Ozonolysis of 1,4-cyclohexadienes in the presence of methanol and acid. Mechanism and intermediates in the conversion of 1,4-cyclohexadiene derivatives to β-keto esters
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Conditions for the preparation of β-keto esters directly from 1,4-cyclohexadiene derivatives are described. This procedure is a further step in the application of the synthetic methodology, which consists of the combination of Birch reduction of available benzene derivatives followed by ozonolysis. In this work, the syntheses of derivatives of dimethyl γ-keto-α-aminoadipate and dimethyl β-keto glutamate from the corresponding 1,4-cyclohexadiene derivatives are described. The latter compounds are prepared from phenylalanine and phenylglycine, respectively. The study of the ozonolysis of simple alkyl derivatives of 1,4-cyclohexadiene in the presence of methanol, both in the presence and absence of acid, helped to establish the mechanism of this reaction. The proximity of the two double bonds, which are cleaved, leads to the intermediate formation of 1,2-dioxolane derivatives that could be identified by NMR spectroscopy. It is shown that regardless of the regioselectivity of the cleavage of the primary ozonide, which is formed, all 1,2-dioxolane derivatives can lead to β-keto esters. This is due to the equilibrium between these dioxolanes in the presence of methanol and acid.
- Gbara-Haj-Yahia, Isra,Zvilichovsky, Gury,Seri, Noa
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p. 4135 - 4139
(2007/10/03)
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- Antioxidation properties of rhodanine and its analogs and derivatives
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A study is made of the antioxidation and antiradical activities of 5-substituted derivatives of rhodanine and a number of its analogs in liquid-phase oxidation of two model compounds, ethylbenzene and Tween-80. Kinetic parameters of inhibited oxidation are determined.
- Epishina,Filippenko,Nikolaevskii,Artemova,Marshtupa
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- High fluorescence specific immune enhancing factor and methods of use for same
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PCT No. PCT/US96/17240 Sec. 371 Date May 27, 1997 Sec. 102(e) Date May 27, 1997 PCT Filed Oct. 25, 1996 PCT Pub. No. WO97/15324 PCT Pub. Date May 1, 1997The present invention relates to a malondialdehyde-acetaldehyde adduct which acts as a specific immune-enhancing factor. In addition to its highly specific and immunogenic properties, the factor is highly fluorescent. It has an excitation frequency of about 398 nanometers and an absorbance of about 460 nanometers. The factor is also highly reactive and is also adducted to antigens including complex proteins, lipids, carbohydrates or DNA.
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- Spectrofluorimetric quantification of malondialdehyde for evaluation of cyclooxygenase-1/Thromboxane synthase inhibition
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The in vitro assay developed by Hartmann and Ledergerber (1995) utilizing the spectrofluorimetric quantification of malondialdehyde after reaction with thiobarbituric acid was modified and used for further investigations. The human whole blood was replaced by a platelet suspension of pig blood, and calcium ionophore A23187 was used instead of collagen for inducing the arachidonic acid cascade. The modified assay represents a simple, time and cost saving method for the evaluation of cyclooxygenase- 1/thromboxane synthase inhibition. The reproducibility and comparability of results is given. Additional experiments allow classification of selective phospholipase A2, cyclooxygenase-1, and thromboxane synthase inhibitors. Further studies of malondialdehyde formation show that the cyclooxygenase and/or the thromboxane synthase are competitively inhibited by reaction products of the cyclooxygenase pathway by a negative feedback mechanism.
- Dannhardt, Gerd,Flemmer, Linda,Hartmann, Rolf W.,Kleber, Alice,Schulze, Elfriede
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p. 359 - 364
(2007/10/03)
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- 1H and 13C NMR spectra and isomerism of 3-aminoacroleins
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A set of 3-alkylaminoacroleins (R1NHCH=CHCH=O, R1 = alkyl) were studied by 13C and 1H NMR spectroscopy in solutions of different solvents and, for the simplest representative of the series, 3-methylaminoacrolein, at different temperatures. The equilibrium solutions of these compounds consists of mixtures of the chelated ZZE form (Z geometry around the =C - C=O single bond and the C=C bond, and E geometry around the C - N bond) and the two E configurational isomers having the E disposition around the =C - C=O single bond and differing in the disposition around the C - N bond (EEZ and EEE forms). The relative proportions of the three isomers depend on solvent polarity, concentration, bulk of substituent R1 and temperature. The EEZ isomer is the most abundant in polar solvents, while the concentration of the ZZE form increases in non-polar solvents and when increasing the bulk of R1. A lineshape 1H NMR study for 3-methylaminoacrolein in CDCl3 gave a ΔG? value of 66.0 kJ mol-1 at 303 K for the EEZ → EEE conversion. The presence of other tautomeric forms was not observed.
- Gomez-Sanchez, Antonio,Paredes-Leon, Rocio,Campora, Juan
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p. 154 - 162
(2007/10/03)
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- New evidence against hydroxyl radicals as reactive intermediates in the thermal and photochemically enhanced fenton reactions
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During the oxidative degradation of 2,4-dimethylaniline (2,4-xylidine) by means of the H2O2/UV method, a series of hydroxylated aromatic amines are formed, this result confirming the role of the hydroxyl radical as an initiator of the oxidative chain reaction. Thermal or photochemically enhanced Fenton reactions in the presence of 2,4-dimethylaniline (2,4-xylidine) yield primarily 2,4-dimethylphenol as an intermediate product, the genesis of which may only be explained by an electron transfer mechanism. Experimental evidence for such a mechanism is presented, and values for the quantum yields of the photochemically enhanced reduction of iron(III) to iron(II) in aqueous solutions of 2,4-xylidine are given.
- Bossmann, Stefan H.,Oliveros, Esther,Goeb, Sabine,Siegwart, Silvia,Dahlen, Elizabeth P.,Payawan Jr., Leon,Straub, Matthias,Woerner, Michael,Braun, Andre M.
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p. 5542 - 5550
(2007/10/03)
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- Liposomes encapsulating doxorubicin
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Liposomes encapsulating doxorubicin, which contain, incorporated into them, a protector compound of general formula A or B, in order to reduce the toxicity of the drug when it is administered in intravenous form, and in which formulas R1 and R2, are the same or different, independently represented by HO--, CH3 O-- or CF3 CH2 O-- STR1
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- STUDIES ON NITROGEN-CONTAINING HETEROCYCLIC COMPOUNDS. SYNTHESES AND REACTIONS OF BENZOQUINOLINE
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The authors devised a new convinient synthesis of benzoquinoline (2) through the condensation of β-naphthylamine with malondialdehyde (MDA) followed by cyclization in polyphosphoric acid.The reactivity of 2 toward N-oxidation, Reissert reaction and methylation with methylsulfinylmethyl carbanion was investigated.
- Takeuchi, Isao,Ushida, Makoto,Hamada, Yoshiki,Yuzuri, Tomoaki,Suezawa, Hiroko,Hirota, Minoru
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p. 2221 - 2232
(2007/10/03)
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- Acyl Migration in the Production of Thymine Propenal from 3'-O-Benzoyl-5'-deoxy-4'-hydroperoxythymidine: A Reinterpretation of a Putative Model for Bleomycin-Mediated DNA Degradation
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Studies of Saito et al. (Saito, I.; Morii, T.; Matsuura, T.J.Org.Chem. 1987, 52, 1008) analyzing the decomposition of 3'-O-benzoyl-5'-deoxy-4'-hydroperoxythymidine (7) claimed to model the decomposition of the putative 4'-hydroxyperoxynucleotide intermediate in the bleomycin (BLM) mediated production of base propenal, 3'-phosphoglycolate, and 5'-phosphate termini from double-stranded DNA.A number of puzzling observations reported in this paper prompted a reinvestigation of this model system in detail. 18O2>-7 and its 4'-epimer 8 were prepared and their fate in aqueous solution as a function of pH was examined.Compound 7 decompos ed in aqueous solution to produce thymine propenal accompanied by stoichiometric formation of benzoate containing 1 atom of 18O.In addition, thymine accompanied by stoichiometric amounts of malondialdehyde and 18O>benzoate was also observed.Acetate containing 1 atom of 18O accompanied production of both thymine and thymine propenal.The ratio of thymine propenal to thymine varied as a function of pH and temperature.Production of 18O>benzoate and a detailed kinetic analysis of the decomposition of 7 unequivocally demonstrated that conversion of 7 to thymine propenal required the intermediacy of a 4'-perbenzoate ester.This perester produced by migration of the 3'-benzoyl blocking group of 7 to the terminal oxygen of its 4'-hydroperoxy moiety would then greatly facilitate heterolytic cleavage of the oxygen-oxygen bond.For stereochemical reasons a similar intramolecular benzoyl migration cannot occur with 8, explaining its lack of reactivity.These results call into question the relevance of the Model proposed by Saito et al. to understanding the base propenal pathway in the BLM-catalyzed degradation of DNA.In addition, preparation of a second model of a putative intermediate in the base propenal pathway, oxy>-3-oxopropyl>thymine (12) is reported.The detailed kinetics of its decomposition as well as identification of the products accompanying ist decomposition are reported.The relevance of these two model systems to the mechanism of degradation of DNA by BLM is discussed.
- McGall, Glenn H.,Stubbe, JoAnne,Kozarich, John W.
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- Ruthenium(II)-Catalyzed Reactions of 1,4-Epiperoxides
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The behavior of 1,4-epiperoxides in the presence of transition-metal complexes is highly dependent on the structures of the substrates and the nature of the metal catalysts.Reaction of saturated epiperoxides such as 1,3-epiperoxycyclopentane, 1,4-epiperoxycyclohexane, or dihydroascaridole catalyzed by RuCl2(PPh3)3 in dichloromethane gives a mixture of products arising from fragmentation, rearrangement, reduction, disproportionation, etc.Prostaglandin H2 methyl ester undergoes clean and stereospecific fragmentation to afford methyl(5Z,8E,10E,12S)-12-hydroxy-5,8,10-heptadecatrienoate and malonaldehyde.Bicyclic 2,3-didehydro 1,4-epiperoxides give the syn-1,2:3,4-diepoxides by the same catalyst.The monocyclic analogues are transformed to a mixture of diepoxides and furan products.The stereochemical outcome of the epoxide formation reflects unique differences in the ground-state geometry of the starting epiperoxide substrates.FeCl2(PPh3)2 serves as a useful catalyst for the skeletal change of sterically hindered bicyclic 2,3-didehydro 1,4-epiperoxides to the syn-diepoxides.In addition, the Fe complex best effects the conversion of 1,4-unsubstituted 2,3-didehydro epiperoxides to furans.The Ru-catalyzed reactions are interpreted in terms of the intermediacy of inner-sphere radicals formed by atom transfer of the Ru(II) species to peroxy substrates, in contrast to the Fe-catalyzed reactions proceeding via free, outer-sphere radicals generated by an electron-transfer mechanism.
- Suzuki, Masaaki,Ohtake, Hiroaki,Kameya, Yoshimi,Hamanaka, Nobuyuki,Noyori, Ryoji
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p. 5292 - 5302
(2007/10/02)
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- SYNTHESIS OF A PROSTAGLANDIN ENDOPEROXIDE MODEL COMPOUND AND ITS REACTION WITH ELECTRON TRANSFER REAGENTS
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5-Exo-phenyl-2,3-dioxabicycloheptane (4c) was synthesized as a model compound of prostaglandin endoperoxide (PGH) to mimic the bioconversion of PGH into thromboxane (TX).The reaction of (4c) with various electron transfer reagents was investigated.With the aid of a catalytic amount of ferrous ion, (4c) was successfully converted into the thromboxane B (TXB) skeleton.
- Takahashi, Kimio,Kishi, Morio
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p. 4737 - 4746
(2007/10/02)
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- An Electron Transfer Model for Thromboxane Biosynthesis
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Conversion of prostaglandin endoperoxide model compound (1) into the thromboxane B ring system (6a) and (7a) was achieved with the aid of the ferrous ion.
- Takahashi, Kimio,Kishi, Morio
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p. 722 - 724
(2007/10/02)
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- Photochemistry and Photophysics of Glycolaldehyde in Solution
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The end products for the photolysis of glycolaldehyde in aqueous solution have been monitored by mass spectrometric, FTIR, 1H NMR, 13C NMR, and UV-vis spectroscopic techniques.Methanol, carbon monoxide, formaldehyde, and malonaldehyde are the major photochemical products and are in accord with earlier CIDNP studies.The quantum yields of fluorescence for glycolaldehyde and a series of related alkanal compounds in solution are reported for the first time; they are all in the range ΦF = 0.71-0.84E-3.The singlet state decay kinetics for glycolaldehyde and ethanal were followed in more detail by measurement of their fluorescence lifetimes in solution with use of a synchrotron radiation source.The results may be explained in terms of emission from "free" and hydrogen-bonded singlet n?* excited states of the carbonyl compounds in water.
- Beeby, Andrew,Mohammed, Dahlan Bin Hj.,Sodeau, John R.
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p. 857 - 861
(2007/10/02)
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- FORMATION AND POLYMERISATION OF MALONALDEHYDE DURING IRRADIATION OF AQUEOUS SOLUTIONS OF D-GLUCOSE AND LACTOSE WITH ULTRASOUND
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Irradiation with ultrasound, vigorous stirring, or vibration of aqueous solutions of D-glucose and lactose can induce chemical reactions.Malonaldehyde has been identified as one product, and the influence of pH and gas atmosphere on its formation by irradiation with ultrasound has been investigated.Only traces were present in neutral solutions, but it was major product in alkaline solutions.Malonaldehyde is unstable, especially in neutral and acidic solutions, and gives 1,3,5-benzenetricarbaldehyde by 1,2-addition and 1 by 1,4-addition.There is evidence that cyclic structures also exist, the ring closure being brought about by an additional hemiacetal bond.To some extent also, 1,3,5-benzenetricarbaldehyde is incorporated into the oligomers.
- Heusinger, Helmut
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- Studies on Paraionic Compounds. Anhydro-1-hydroxy-3-oxopyrazolopyrazolium Hydroxides. Formation and Stability of a Novel Series of 4n? Heterocyclic Betaines.
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Different substituted anhydro-1-hydroxy-3-oxopyrazolopyrazolium hydroxides were prepared by the reaction of 1,3-dicarbonyl compounds with derivatives of 4-phenyl-3,5-dihydroxypyrazole.These diazapentalene derivatives belong to new series of 4n? cyclic betaines which are named "paraionic" heterocycles.The effects of substituents on the stability of both the anionic and the cationic rings were kinetically studied.Selective cleavage of either the anionic or the cationic ring was achieved by varying the conditions of the reaction with morpholine.Electron releasing groups on the cationic ring and electron attracting groups on the anionic ring enhance the stability of the bicyclic system.They also cause a hypsochromic shift of the visible light absorption.
- Zvilichovsky, Gury,David, Mordechai
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p. 295 - 300
(2007/10/02)
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- STRUCTURE OF A NEW MODIFIED NUCLEOSIDE FORMED BY GUANOSINE-MALONALDEHYDE REACTION
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A new modified nucleoside was formed by the reaction of guanosine with malonaldehyde under acidic condition.This compound emitted strong yellow fluorescence and was hydrolyzed by NaOH into guanosine and malonaldehyde.Its structure was determined to be 1,N2-(1-propenyl-3-ylidene)guanosine by the spectroscopic analysis.
- Seto, Hiroshi,Akiyama, Kazuyuki,Okuda, Taisuke,Hashimoto, Tsuyoshi,Takesue, Tomoyuki,Ikemura, Tadashi
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p. 707 - 708
(2007/10/02)
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