• Journal of Photoscience
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• 제10권1호
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• pp.9-20
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• 2003

Recent studies on the photoreactivity of l,4-unsaturated systems have changed some ideas that were firmly established in this area of research for many years. Thus, we have described the first examples of 2-aza-di-$\pi$-methane (2-ADPM) rearrangements promoted by triplet-sensitization and by single electron transfer (SET) using electron-acceptor sensitizers. These reactions afford N-vinylaziridine and cyclopropylimine photoproducts in the first examples of di-$\pi$-methane processes that yield three-membered ring heterocycles. l-Aza-1,4-dienes also undergo SET-promoted l-aza-di-$\pi$-methane (l-ADPM) rearrangements via radical-cation intermediates using electron acceptor sensitizers. In some cases, alternative cyclizations yielding different carbocycles and heterocycles have been observed. The l-ADPM and di-$\pi$-methane (DPM) reactions also occur via radical-anion intermediates on irradiation using electron donor sensitizers. On the other hand, the photoreactivity reported for $\beta$,${\gamma}$-unsaturated aldehydes for many years was decarbonylation to the corresponding alkenes. However, our studies demonstrate that these compounds undergo the oxa-di-$\pi$-methane (ODPM) rearrangement with high chemical and quantum efficiency. A comparison of the photochemical reactivity of $\beta$,${\gamma}$-unsaturated aldehydes and corresponding methyl ketones has shown that the ketones do not undergo the ODPM rearrangement while the corresponding aldehydes are reactive by this pathway. Monosubstituted $\beta$,${\gamma}$-unsaturated aldehydes at C-2 undergo the ODPM rearrangement yielding the corresponding cyclopropane carbaldehydes diastereoselectively. Finally, we have described the first examples of reactions, similar to the well know Norrish Type I process, which take place in the triplet excited state of $\beta$,${\gamma}$-unsaturated carbonyl compounds by excitation of the C-C double bond instead of the carbonyl group.

• Molecular & Cellular Toxicology
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• 제1권2호
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• pp.111-115
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• 2005

Ultraviolet (UV) radiation to mammalian skin is known to alter cellular function via generation of Reactive Oxygen Species (ROS), DNA damage and DNA lesions, such as pyrimidine dimmers and photoproducts, which could lead to DNA mutation if they are not repaired. In this study, we have investigated the reduction of DNA damage and of apoptosis with a particular attention to genetic effect of paeoniflorin in Normal Human Epidermal Keratinocytes (NHEK). After UVB irradiation from $10\;to\;500mJ/cm^{2}$ to NHEK, Mean Tail Moments (MTM) were increased with UVB dose increase. The greatest amount of strand breaks was induced at $500mJ/cm^{2}$ of UVB. Even at the lowest dose of UVB ($10mJ/cm^{2}$), change in MTM was detected (P<0.0001). Pretreated cell with 0.1% paeoniflorin maximally reduced the level of DNA damage to about 21.3%, compared to untreated cell. In the lower concentrations less than 0.01% of paeoniflorin, MTM had a small increase but paeoniflorin still had reductive effects of DNA damage. We measured the apoptosis suppression of paeoniflorin with annexin V flous staining kit. As we observed under the fluorescence microscopy to detect apoptosis in the irradiated cell, the fluorescence intensity was clearly increased in the untreated cell, but decreased in treated cells with paeoniflorin. These results suggest that paeoniflorin reduces the alteration of cell membranes and prevents DNA damage. Therefore, the use of paeoniflorin as a free radical scavenger to reduce the harmful effects of UV lights such as chronic skin damage, wrinkling and skin cancer can be useful to prevent the formation of photooxidants that result in radical damage.

• Bulletin of the Korean Chemical Society
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• 제31권9호
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• pp.2453-2458
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• 2010

Photochemical studies of N-[(trimethylsilyl)alkyl]saccharins were carried out to investigate their photochemical behavior. Depending on the nature of the substrate and the solvent system employed, reactions of these substances can take place by either SET-promoted silyl migration from carbon to either the amide carbonyl or sulfonyl oxygen or by a N-S homolysis route. The results of the current studies show that an azomethine ylide, arising from a SET-promoted silyl migration pathway, is generated in photoreactions of N-[(trimethylsilyl)methyl]saccharin and this intermediate reacts to give various photoproducts depending on the conditions employed. In addition, irradiation of N-[(trimethylsily)ethyl]saccharin produces an excited state that reacts through two pathways, the relative importance is governed by solvent polarity and protic nature. Finally, photoirradiation of N-[(trimethylsilyl)propyl]saccharin in a highly polar solvent system comprised of 35% aqueous MeOH gives rise to formation of a tricyclic pyrrolizidine and saccharin that generated via competitive SET-promoted silyl transfer and $\gamma$-hydrogen abstraction pathways.

• Toxicological Research
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• 제31권2호
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• pp.97-104
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• 2015

The skin exposure to solar irradiation and photoreactive xenobiotics may produce abnormal skin reaction, phototoxicity. Phototoxicity is an acute light-induced response, which occurs when photoreacive chemicals are activated by solar lights and transformed into products cytotoxic against the skin cells. Multifarious symptoms of phototoxicity are identified, skin irritation, erythema, pruritis, and edema that are similar to those of the exaggerated sunburn. Diverse organic chemicals, especially drugs, are known to induce phototoxicity, which is probably from the common possession of UV-absorbing benzene or heterocyclic rings in their molecular structures. Both UVB (290~320 nm) and UVA (320~400 nm) are responsible for the manifestation of phototoxicity. Absorption of photons and absorbed energy (hv) by photoactive chemicals results in molecular changes or generates reactive oxygen species and depending on the way how endogenous molecules are affected by phototoxicants, mechanisms of phototoxcity is categorized into two modes of action: Direct when unstable species from excited state directly react with the endogenous molecules, and indirect when endogeneous molecules react with secondary photoproducts. In order to identify phototoxic potential of a chemical, various test methods have been introduced. Focus is given to animal alternative test methods, i.e., in vitro, and in chemico assays as well as in vivo. 3T3 neutral red uptake assay, erythrocyte photohemolysis test, and phototoxicity test using human 3-dimensional (3D) epidermis model are examples of in vitro assays. In chemico methods evaluate the generation of reactive oxygen species or DNA strand break activity employing plasmid for chemicals, or drugs with phototoxic potential.

• 한국환경농학회지
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• 제40권1호
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• pp.13-19
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• 2021

BACKGROUND: Chemicals such as antibiotics and surfactants can enter agricultural environment and they can be degraded by natural processes such as photolysis. These chemicals exist in mixtures in the environment, but studies on degradation of the mixtures are limited. This study compares the photodegradation of Triton X-100 (TX) and antibiotics [tetracycline (TC) and sulfathiazole (STH)] when they are in a single solution or in mixtures. METHODS AND RESULTS: TC, STH, and TX solutions were exposed to UV-A for the photodegradation tests for 14 days. The residual TC, STH, and TX concentrations were analyzed by using HPLC. The TC degradation was similar regardless of the presence of TX, while the TX degradation was lower in the presence of TC. The STH degradation was similar regardless of the presence of TX, while the TX degradation was greater in the presence of STH. However, the STH degradation was slower in the TC-STH-TX mixture than in the STH-TX mixture. Also, the TX degradation was negligible in the TC-STH-TX mixture. The results show that the photodegradation of TC, STH, and TX can be different in mixtures. This can be attributed to the different emission and absorption wavelengths of each compound and interaction between these compounds and photoproducts. CONCLUSION: Overall, this study emphasizes that photodegradation of single chemicals and chemical mixtures can be different, and more studies on single compounds as well as mixtures are required to understand the fate of chemicals in the environment in order to manage them properly.

• Journal of Veterinary Science
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• 제23권4호
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• pp.62.1-62.10
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• 2022

Background: The corneal and limbal morphology relevant to corneal epithelial maintenance in ten different species was examined using histological methods. Objectives: The presence of a Bowman's layer, limbal epithelial cell, and superficial stromal morphology was examined in the following species to evaluate the differences in corneal thickness and epithelium: Java sparrows, frogs, macaws, spoonbills, red pandas, penguins, horses, Dobermans, orangutans, and humans. Methods: Corneal sections (4 ㎛) were obtained from ten ocular globes from three different animal classes: Aves, Amphibia, and Mammalia. All sections were stained with hematoxylin and eosin and periodic acid-Schiff reaction. After microscopy, all stained slides were photographed and analyzed. Results: Significant morphological differences in the corneal and limbal epithelia and their underlying stroma between species were observed. The number of corneal epithelial cell layers and the overall corneal epithelial thickness varied significantly among the species. The presence of a Bowman's layer was only observed in primates (orangutans and humans). Presumed supranuclear melanin caps were noted in four species (orangutans, macaws, red pandas, and horses) in the limbal basal epithelial layer (putative site of corneal epithelial stem cells). The melanin granules covered the apex of the cell nucleus. Conclusions: Supranuclear melanin capping has been described as a process within the epidermis to reduce the concentration of ultraviolet-induced DNA photoproducts. Similarly, there may be a relationship between limbal stem cell melanin capping as a protective mechanism against ultra-violet radiation.

• Applied Biological Chemistry
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• 제18권1호
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• pp.30-41
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• 1975

환경요인(環境要因)으로서 일광(日光), 미생물(微生物), 그리고 벼의 추출액(抽出液)에 존재(存在)하는 조효소(粗酵素)에 의(依)한 치환(置換) Diphenyl Ether계(系) 제초제(除草劑)의 일종(一種)인 MC-4379를 분해(分解)하여 그 분해산물(分解産物)을 TLC, GLC, IR등으로 분석확인(分析確認)하고 모화합물(母化合物)과 분해산물(分解産物)의 식물생육(植物生育)에 대(對)한 조해력(阻害力)을 시험(試驗) 하였다. 그 결과(結果)를 요약(要約)하면 다음과 같다. 1. MC-4379는 광분해(光分解) 결과(結果) amino-MC-4379, 2,4-dichloro-3'-carboxyl-4'-nitro-diphenyl ether, Nitrofen, 2,4-dichloro-3'-carboxyl-4'-amino-diphenyl ether, amino-Nitrofen, 3-carboxymethyl-4-nitrophenel, p-nitrophenol, p-aminophenol과 소량(少量)의 미지화합물(未知化合物)이 생성(生成) 되었고 모화합물(母化合物)은 대부분(大部分) 작용(作用)을 받지 않은 채로 남아 있었다. 또한 photosensitizer로 알려진 benzophenone을 가(加)하면 광분해(光分解)가 더욱 촉진(促進)됨을 확인(確認)하였다. 2. 조효소액(粗酵素液)에 의(依)한 MC-4379의 분해시(分解時)에는 Nitrofen과 소량(少量)의 미지화합물(未知化合物)이 확인(確認)되었으며 대부분(大部分)의 모화합물(母化合物)은 작용(作用)을 받지 않은 채로 존재(存在)하고 있음을 알 수 있었다. 3. Pseudomonas cruciviae와 Aspergillus ustus에 의(依)한 분해시(分解時)에는 Nitrofen과 amino-MC-4379 및 소량(少量)의 미지화합물(未知化合物)이 생성(生成)되었으며 대부분(大部分)은 작용(作用)을 받지않은 모화합물(母化合物)의 형태(形態)로 존재(存在)하였다. 4. MC-4379와 그 분해산물(分解産物) 및 타종(他種) Diphenyl Ether제초제(除草劑)가 식물(植物)의 생육(生育)에 미치는 조해력(阻害力)을 시험(試驗)한 결과(結果) 벼에 있어서는 이들 각화합물(各化合物)(1,000 ppm 유화액(乳化液))의 생육조해력(生育阻害力)은 p-nitrophenol> C-6989 > Nitrofen> amino-nitrofen> MC-4379의 순위(順位)이었고 대두(大豆)에 있어서는 Nitrofen> amino-Nitrofen>MC-4379 의 순위(順位)였다. 잡초중(雜草中) 비름(Amantus blitum)과 강아지풀(Setaria viridis)의 발아(發芽)된 종자(種子)를 사용(使用)하여 이들 화합물(化合物)(500ppm)의 현탁액중(懇濁液中)에서 생육(生育)시켜본 결과(結果) 3일후(日後)에 모두 고사(枯死)하는 현상(現象)을 관찰(觀察)할 수 있었다.