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The Chemical Synthesis of Lipid A
Published in Helmut Brade, Steven M. Opal, Stefanie N. Vogel, David C. Morrison, Endotoxin in Health and Disease, 2020
Shoichi Kusumoto, Koichi Fukase, Masato Oikawa
The successful synthetic work during 1982–1987 was of great value in giving the final structural proof for the active entity and opening an entirely new era of endotoxin research (12). The structure proposed for lipid A was chemically constructed de novo as shown in Figure 3 (1,2). It thus became theoretically possible to obtain any related structures as desired. But the synthetic route contained many steps of chemical transformation, and there still remained several important points to be improved in order to make the chemical synthesis a truly efficient and useful tool. The major areas to be improved were (1) selection of protecting groups and their efficient and regioselective introduction onto the carbohydrate or fatty acyl moieties (creation of new protecting procedures was also important), (2) elaboration of efficient and reproducible reaction conditions for glycosyl phosphorylation and the work-up procedure after that step, (3) establishing a method for the purification of the final deprotected products. During the past decade, most of these problems have been greatly resolved by continuous efforts of synthetic chemists. Chemical synthesis has now become a valuable tool in the field.
Dietary Isoflavones-Mechanism and Efficacy in Cancer Prevention and Treatment
Published in Sheeba Varghese Gupta, Yashwant V. Pathak, Advances in Nutraceutical Applications in Cancer, 2019
Richa Dayaramani, Jayvadan K. Patel
The glycoside, acetyl, and malonyl forms of isoflavones get converted into the corresponding aglycone derivatives by degradation into the acidic or alkaline medium. The transformation of acetyl and malonyl esters into the respective glycoside by hydrolysis and decarboxylation of malonyl glycoside into the aglycone are a most common form of chemical transformation. The formation of aglycone isoflavones takes place by degradation of the glycosidic bond (Figure 15.6) [20].
The Molecular Genetics OF DNA Methylation in Colorectal Cancer
Published in Leonard H. Augenlicht, Cell and Molecular Biology of Colon Cancer, 2019
We chose to use C3H 10T1/2 cells as a model system for several reasons. There is a remarkably low background transformation frequency;106 and the cells show a high frequency of transformation by a variety of carcinogens, and for this reason they are widely used as a model system for chemical transformation.59, 107, 108 Transformation by 5-azaCR does not appear to arise by point mutation, in that the measured mutation frequency is several orders of magnitude lower than the transformation frequency.62 Finally, a striking feature of 5-azaCR-induced transformation is the long latency at which the transformed phenotype arises. In particular, when cells are treated with 5-azaCR for 24 hr, washed and allowed to grow to confluence, transformed foci do not appear until several weeks after confluence is reached.59,109
X-ray spectrometry imaging and chemical speciation assisting to understand the toxic effects of copper oxide nanoparticles on zebrafish (Danio rerio)
Published in Nanotoxicology, 2022
Joyce Ribeiro Santos-Rasera, Rafael Giovanini de Lima, Dejane Santos Alves, Regina Teresa Rosim Monteiro, Hudson Wallace Pereira de Carvalho
There are few reports on the chemical transformation of metals in fish. The most studied species in this type of analysis is Oncorhynchus mykiss. Table 3 shows some studies with this species and analyzes of XAS or XANES to determine the chemical environment within the organism. Differently from our study, in all of them, the compound, after the exposure period, was bound to some amino acid, such as cystine, histidine or methionine. However, none of these studies are on zebrafish exposed to a copper source. Our results show that, under the described experimental conditions, no chemical transformation of copper was detected in the zebrafish. This fact may be related to some factors related to ecotoxicology such as exposure time, the source of copper, and the concentration of copper into zebrafish. However, it should be borne in mind that the relatively low sensitivity of the technique will hardly detect compounds whose weight fraction is below 5%. For this, smaller beam size can be an alternative to obtain more detailed data about the chemical environment of these organisms, especially in regions with smaller concentration of the element of interest.
Manganese dioxide nanosheets induce mitochondrial toxicity in fish gill epithelial cells
Published in Nanotoxicology, 2021
Cynthia L. Browning, Allen Green, Evan P. Gray, Robert Hurt, Agnes B. Kane
Chemical transformation and dissolution pathways and kinetics are key determinants of 2D nanomaterial toxicity (Gray et al. 2018, 2020; Tan et al. 2019). The unique structure, shape and high surface area of 2D nanosheets can impact their rate of dissolution in environmental and biological media. A case study of MnO2 nanosheets for example, showed that this nanomaterial is stable in pure water, but undergoes dissolution in the presence of common biological reducing agents, releasing toxic manganese ions (Mn2+) (Gray et al. 2020). The 2D MnO2 nanosheets had significantly faster dissolution kinetics than their MnO2 microparticle counterparts (Gray et al. 2020), exemplifying the importance of shape and/or surface area in determining the dissolution behavior of the 2D nanosheets. Since MnO2 nanosheets undergo reductive dissolution (involving electron donors that convert Mn(IV) to Mn(II)), they are likely to be stable in some aquatic environments, and undergo dissolution after being taken up by a target organism containing physiological reducing agents, both extracellular and intracellular.
Engineering a yeast double-molecule carrier for drug screening
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2018
Qiyun Zhang, Sheng Hu, Ke Wang, Min Cui, Xiaohua Li, Mo Wang, Xuebo Hu
Yeast culture and transformation: Plasmid was transformed into yeast strain S. cerevisiae EBY100 by standard chemical transformation as previously described with a Frozen-EZ yeast transformation kit (Zymo Research, Irvine, CA) [12]. Briefly, transformed colonies were inoculated into SDCAA media (20 g/L dextrose, 6.7 g/L Difco yeast nitrogen base, 5 g/L Bacto casamino acids, 5.4 g/L Na2HPO4 and 8.56 g/L NaH2PO4·H2O) and cultured at 30 °C with shaking. After 24 h of culture in SDCAA, yeast cells were transferred to SGCAA media (20 g/L galactose, 6.7 g/L Difco yeast nitrogen base, 5 g/L Bacto casamino acids, 5.4 g/L Na2HPO4, 8.56 g/L NaH2PO4·H2O) and cultured for another 24 h at 30 °C with shaking to induce protein expression.