• Mass Spectrometry Letters
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• v.9 no.1
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• pp.37-40
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• 2018

Farinomalein is a maleimide-bearing compound well known for its anti-fungal activity. In the present study, synthesis of farinomalein is achieved via Stobbe condensation followed by Haval-Argade contrathermodynamic rearrangement. Kinetically driven Stobbe condensation followed by condensation with beta-alanine reveals formation of two isomers of farinomalein. This article describes application of LC-MS/MS in structure elucidation of farinomalein 1 and its isomers 2 and 3 encountered in its synthesis. The proposed distinct fragmentation pathway is supported by rational organic reaction mechanism. These fragmentation pathways are significant for analytical method development of farinomalein in near future. The structures of farinomalein 1 and its isomers 2 and 3 have been assigned undisputedly.

• Preventive Nutrition and Food Science
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• v.2 no.4
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• pp.360-367
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• 1997

The chemistry background of the Maillard reaction focused on pyrazines and factors affecting the reaction products were reviewed. The Maillard reaction, also called a non-enzymatic browning reaction, is quite complex and generates numerous reaction products. In processed foods, it is generally accepted as a key reaction to produce flavor components. Specially, pyrazines possess an important impact character on the roasted foods with other heterocyclic compounds. The Maillard reaction is initiated by condensation between reducing sugar and amino group, and N-glycosylamines are produced via Schiff base with dehydration of water. After the rearrangement of the N-glycosylamines, they follow transformation into deoxyhexosones which are reactive intermediates. Degradation and fragmentation are facilitated by rearranged compounds. By condensation, pyrazine, one of the final Maillard products, is generated as a relatively stable form to provide specific aromas. During the processes of the reaction, chemical or physical environmental parameters affect the formation of the products.

• Mass Spectrometry Letters
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• v.6 no.3
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• pp.65-70
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• 2015

N-Alkyl/benzyl substituted isatin derivatives are intermediates and synthetic precursors for the preparation of biological active heterocycles. N-alkyl/benzyl isatins have showed various biological activities, such as cytotoxicity, antiviral, caspase inhibition, cannabinoid receptor 2 agonists for the treatment of neuropathic pain, etc. In this study, N-alkyl/benzyl isatin derivatives were synthesized from isatin and alkyl/benzyl halides in presence of K₂CO₃ in DMF and excellent to quantitative yields (~95%) were obtained. Isatins and benzyl-isatins were condensed with fluorescein hydrazide to form fluorescein hydrazone. All the compounds were subjected to their fragmentation behavior study using LC/MSⁿ. N-Alkyl substituted isatin derivatives fragmented at nitrogen-carbon (N-C) bond, hence gave daughter ion as [RN+H]⁺. Whereas, N-benzyl substituted isatin derivatives fragmented at carbon-carbon (C-C) bond of alkyl chain which linked with nitrogen molecules, therefore gave N-methyl fragments [RNCH₂]⁺. This study demonstrated that, isatin moiety present in a small/large molecule or in a matrix of reaction mixture with/without N-alkyl/benzyl substituents can be identified by mass spectroscopic fragmentation behavior study.

• Archives of Pharmacal Research
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• v.3 no.2
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• pp.87-88
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• 1980

The goal of this research is to provide information that will lead to the development of new non-phototoxic antimalarial compounds. The goal was approached by first learning the chemical mechanism of phototoxicity of six representative compounds 1a-f: a[(diethyl-, -dihexyl-, and -dioctyl- aminomethyl)]-2-(3', 4' -dichlorophenyl)-6-methoxy-4-quinolinemethanol (1a, 1b, and 1c) and .alpha. [(diethyl-, -dibutyl-, and -dihexyl-aminomethyl)]-2-(-4'-methoxyphenyl-6-methoxy-7-chloro-4-quinolinemethan ol (1d, 1e, and 1f). The photochemical reaction of these compounds was investigated in 2-propanol. Similar photochemical fragmentation reactions accurred in all compounds.

• Clinical and Experimental Reproductive Medicine
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• v.29 no.2
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• pp.105-115
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• 2002

Objective : To evaluate the effects of the reactive oxygen species (ROS) generated with a xanthine (X) and xanthine oxidase (XO) system on sperm function, the change of sperm characteristics, lipid peroxidation, and DNA fragmentation in bovine spermatozoa. Materials and Methods: ROS were produced using a combination of 1000 uM X and 50 mU/ml XO. The ROS scavengers: superoxide dismu tase (SOD) (200 U/ml) and catalase (500 U/ml) were also tested. Spermatozoa were incubated for 2 hours in BWW medium with a combination of X-XO supplemented with or without ROS scavengers at $37^{circ}C$ under 5% $CO_2$ incubator. Sperm movement characteristics by CASA (computer-aided sperm analysis), HOST (hypoosmotic swelling test), Caionophore induced acrosome reaction, malondialdehyde formation for the analysis of lipid peroxidation, the percentage of DNA fragmentation using the method of TdT-mediated nick end labelling (TUNEL) by flow cytometry were determined after 2 hours incubation. Results: The action of ROS on bovine spermatozoa resulted in a decreased in capacity for sperm motility, Ca-ionophore induced acrosome reaction and membrane integrity, an increased in malondialdehyde formation and the percentage of sperm with DNA fragmentation. In the effects of antioxidant, catalase completely alleviated the toxic effects induced by the ROS in terms of sperm function and characteristics, however SOD exhibited no capacity to reduce the toxic effects. Conclusion: The ROS can induce significant damages to sperm functions and characteristics. The useful ROS scavengers can minimized the defects of sperm function and various damages of spermatozoa.

• Journal of Embryo Transfer
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• v.25 no.2
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• pp.111-116
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• 2010

Sperm chromatin integrity is essential for successful fertilization and development of an embryo. Reported here is a quantification of DNA fragments which is intimately associated with reproductive potential to provide one of criteria for sperm chromatin integrity. Three sperm populations were considered: CONTROL (no treatment), UV irradiation (48mW/$cm^2$, 1h) and $H_2O_2$ (oxidative stress induced by hydrogen peroxide, 10 mM, 50 mM and 100 mM). DNA fragments in boar sperm were evaluated by using ligation-mediated quantitative real-time polymerase chain reaction (LM-qPCR) assay, which relies on real-time qPCR to provide a measure of blunt 5' phosphorylated double strand breaks in genomic DNA. The results in agarose gel electrophoresis showed no significant DNA fragmentation and no dose-dependent response to $H_2O_2$. However, the remarkable difference in shape and position was observed in melting curve of LM-qPCR. This result supported that the melting curve analysis of LM-qPCR presented here, could be more sensitive and accurate than previous DNA fragmentation assay method.

• Clinical and Experimental Reproductive Medicine
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• v.49 no.4
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• pp.270-276
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• 2022

Objective: The present study assessed the biological characteristics of human spermatozoa at different time intervals (0, 1, 1.5, and 2 hours) after incubation at 37℃. Methods: Twenty-five normozoospermic semen samples were incubated at 37℃. Incubation was performed at four time intervals of 0 (after liquefaction), 1, 1.5, and 2 hours. The samples were evaluated for sperm parameters at each time interval. Results: The rate of sperm progressive motility decreased at 1.5 hours compared to 0 hours as well as 2 hours compared to 1 hour and 0 hours. The rate of non-motile spermatozoa also decreased after 2 hours compared to after 0 hours. No significant changes were observed in sperm viability (p=0.98) and non- progressive motility (p=0.48) at any time intervals. Abnormal sperm morphology increased at 1.5 hours of incubation time (p<0.001). No significant changes were observed in DNA fragmentation at 1 hour compared to 0 hours (median [interquartile range]: 19.5 [4] vs. 19 [4]), as well as at 1.5 hours compared to 1 hour (20 [5]). However, a significant increase in DNA fragmentation was observed at 1.5 hours compared to 0 hours. The mitochondrial membrane potential decreased remarkably after 1 hour of incubation time. No significant differences were observed in the acrosome reaction or malonaldehyde levels at any time point (p=0.34 and p=0.98, respectively). Conclusion: The incubation of normozoospermic samples before use in assisted reproductive technology should be less than 1.5 hours to minimize the destructive effects of prolonged incubation time on general and specific sperm parameters.

• Journal of the Korean Wood Science and Technology
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• v.47 no.4
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• pp.442-450
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• 2019

Despite its potential as a renewable source for fuels and chemicals, lignin valorization still faces technical challenges in many aspects. Overcoming such challenges associated with the chemical recalcitrance of lignin can provide many opportunities to innovate existing and emerging biorefineries. In this work, we leveraged a biomass genetic engineering technology to produce phenolic aldehyde-rich lignin structure via downregulation of cinnamyl alcohol dehydrogenase (CAD). The structurally altered lignin obtained from the Arabidopsis thaliana CAD mutant was pyrolyzed to understand the effect of structural alteration on thermal behavior of lignin. The pyrolysis was conducted at 400 and $500^{\circ}C$ using an analytical pyrolyzer connected with GC/MS and the products were systematically analyzed. The results indicate that aldehyde-rich lignin undergoes fragmentation reaction during pyrolysis forming a considerable amount of C6 units. Also, it was speculated that highly reactive phenolic aldehydes facilitate secondary repolymerization reaction as described by the lower yield of overall phenolic compounds compared to wild type (WT) lignin. Quantum mechanical calculation clearly shows the higher electrophilicity of transgenic lignin than that of WT, which could promote both fragmentation and recondensation reactions. This work provides mechanistic insights toward biomass genetic engineering and its application to the pyrolysis allowing to establish sustainable biorefinery in the future.

• YAKHAK HOEJI
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• v.23 no.3_4
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• pp.167-171
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• 1979

It is knwon that in the reaction of .alpha.-diethylaminoacetophenone with potassium cyanide and ammonium carbonate in dilute alcohol solution, 5-phenylhydantoin is formed. In this study the mechanism of the reaction by which diethylaminomethyl group is eliminated, was investigated with applying GC/MS-system. From the fragmentation pattern of mass spectrum of the unknwon compound, which has mol peak 112, it was identified as diethylaminoacetonitrile. According to our GC/MS study of the reaction mixture, it seems likely that diethylaminomethyl group is eliminated neither through the alkali degradation of .alpha.-diethylaminoacetophenone to aldehyde nor after the anticipated hydantoin formation. But it is believed that in the course of ring formation through an unidentified mechanism diethylaminomethyl group is eliminated.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.4
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• pp.411-420
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• 2018

This study presents a revised crackling core model for the description of $UO_2$ sphere oxidation in air atmosphere. For close reproduction of the sigmoid behavior exhibited in $UO_2$ to $U_3O_8$ conversion, the fragmentation effect contributing to the increased reactive surface area and the concept of variable grain conversion time were considered in the model development. Under the assumptions of two-step successive reaction of $UO_2{\rightarrow}U_3O_7{\rightarrow}U_3O_8$ and final grain conversion time equivalent to ten times the initial grain conversion time, the revised model showed good agreement with the experimental data measured at 599 - 674 K and a lowest deviation when compared with Nucleation and Growth model and AutoCatalytic Reaction model. The evaluated activation energy at 100% conversion to $U_3O_8$, $57.6kJ{\cdot}mol^{-1}$, was found to be closer to the experimentally extrapolated value than to the value determined in AutoCatalytic Reaction model, $48.6kJ{\cdot}mol^{-1}$.