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Ultraviolet and Light Absorption Spectrometry
Published in Adorjan Aszalos, Modern Analysis of Antibiotics, 2020
Zoltan M. Dinya, Ferenc J. Sztaricskai
In contrast to the penam skeleton (22), the 3-cephem skeleton (23) contains a characteristic chromophoric system, and thus cephalosporins show absorption maxima at 260—266 nm [normal cephalosporins (2), R1 = H] or at 240—243 nm and 264—266 nm [7α-methoxycephalosporins (2), R1 = OCH3].
Tebipenem, the first oral carbapenem antibiotic
Published in Expert Review of Anti-infective Therapy, 2018
Akash Jain, Luke Utley, Thomas R. Parr, Thomas Zabawa, Michael J. Pucci
The carbapenems, members of the β-lactam class of antibiotics, are specifically characterized by an all-carbon fused five-membered ring system (as compared to the presence of a sulfur atom in the penam class of molecules), as well as unsaturation in the ring between C2 and C3 (Figure 1). Efficient synthesis of the carbapenem core has proven essential for the development of novel compounds, resulting in a number of new analogs that address significant deficiencies in early carbapenems. Development of a streamlined synthesis of β-methylazetidine-2-one allows for the rapid assembly of carbapenem analogs with methyl-substitution at the 1-position, a key structural feature in carbapenems such as tebipenem as shown compared with other marketed carbapenems in Figure 2. Tebipenem is structurally characterized by a traditional β-methyl carbapenem core, a unique bicyclic azetidine, thiazole moiety at the 2-position, and a prodrug pivoxil ester at the 3-position. The addition of this ester group was determined to greatly improve oral bioavailability [23]. An inexpensive and rapid isocratic LC method has recently been reported for the quantitative determination of tebipenem [24,25].
Effects of spaceflight on the composition and function of the human gut microbiota
Published in Gut Microbes, 2020
Zizhong Liu, Gui Luo, Ruikai Du, Weijia Sun, Jianwei Li, Haiyun Lan, Pu Chen, Xinxin Yuan, Dengchao Cao, Yuheng Li, Caizhi Liu, Shuai Liang, Xiaoyan Jin, Ruifu Yang, Yujing Bi, Yanping Han, Ping Cao, Wei Zhao, Shukuan Ling, Yingxian Li
Recent studies on microbiology in space have revealed that spaceflight has an important influence on bacterial resistance genes. The results of this study showed that the only unique enzyme reactions affected by spaceflight were those involved in biosynthesizing antibiotics. Thus, we analyzed the resistance genes in the gut microbiotas from missions one and two. The total resistance genes in the gut microbiota were no significant differences between R + 1 and R + 28D in mission one (Figure 4a). We also showed the top twenty abundances of antibiotic resistance ontologies (AROs) in the gut microbiota (Figure 4b). Some AROs had altered markedly after spaceflight; for example, the abundance of evgS, which is related to macrolide, fluoroquinolone, penam, and tetracycline resistance, was increased in R + 1 compared with that in R + 28 in mission one (Supplementary figure 12a and 12b). The total number of resistance genes in the gut microbiota was increased in R + 1 compared with that in L-7 in mission two (Figure 4c) and was also increased compared with that of R + 28 except in subject S2.02. The top twenty ARO abundances in the gut microbiota are shown (Figure 4d). Some of these AROs were also influenced markedly by spaceflight, but the fluctuation trend was inconsistent between the two subjects. For example, the abundance of evgS in the gut microbiota of subject S2.02 was increased in R + 1 compared with L-7 and R + 28, while in subject S2.01 was decreased (Supplementary figure 12c). LEfSe analysis was used to obtain the difference AROs, and we compared the ARO abundance of R + 1 with that of R + 28 from mission one. The LDA score of the AROs above 2 and the distribution diagram of the AROs and the cluster heat map are shown (Figure 4e,f). The abundances of 5 AROs were increased, and those of 3 AROs were decreased in R + 1 compared with that in R + 28.