• Title/Summary/Keyword: A321

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Improving amber suppression activity of an orthogonal pair of Saccharomyces cerevisiae tyrosyl-tRNA synthetase and a variant of E. coli initiator tRNA, fMam tRNACUA, for the efficient incorporation of unnatural amino acids (효율적인 비천연 아민노산 도입을 위한 효모균 타이로신-tRNA 합성효소와 대장균 시작 tRNA 변이체의 엠버써프레션 활성증가)

  • Tekalign, Eyob;Oh, Ju-Eon;Park, Jungchan
    • Korean Journal of Microbiology
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    • v.54 no.4
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    • pp.420-427
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    • 2018
  • The orthogonal pair of Saccharomyces cerevisiae tyrosyl-tRNA synthetase (Sc YRS) and a variant of E. coli initiator tRNA, fMam $tRNA_{CUA}$ which recognizes the amber stop codon is an effective tool for site-specific incorporation of unnatural amino acids into the protein in E. coli. To evolve the amber suppression activity of the orthogonal pair, we generated a mutant library of Sc YRS by randomizing two amino acids at 320 and 321 which involve recognition of the first base of anticodon in fMam $tRNA_{CUA}$. Two positive clones are selected from the library screening with chloramphenicol resistance mediated by amber suppression. They showed growth resistance against high concentration of chloramphenicol and their $IC_{50}$ values were approximately 1.7~2.3 fold higher than the wild type YRS. In vivo amber suppression assay reveals that mutant YRS-3 (mYRS-3) clone containing amino acid substitutions of P320A and D321A showed 6.5-fold higher activity of amber suppression compared with the wild type. In addition, in vitro aminoacylation kinetics of mYRS-3 also showed approximately 7-fold higher activity than the wild type, and the enhancement was mainly due to the increase of tRNA binding affinity. These results demonstrate that optimization of anticodon recognition by engineered aminoacyl tRNA synthetase improves the efficiency of unnatural amino acid incorporation in response to nonsense codon.

Sensing Period Adaptation using the Cost Function in the Cognitive Radio Networks (인지 무선 네트워크에서 시스템 비용함수를 이용한 적응적 센싱주기)

  • Gao, Xiang;Park, Hyung-Kun
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.61 no.2
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    • pp.321-323
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    • 2012
  • Cognitive radio has been recently proposed to dynamically access unused-spectrum. Since the spectrum availability for opportunistic access is determined by spectrum sensing, sensing is identified as one of the most crucial issues of cognitive radio networks. The PHY-layer sensing, as a part of spectrum sensing in cognitive radio, concerns the sensing mechanism to determine channel to be sensed and to access. One of the important issues in the PHY-layer sensing control is to find an available sensing period and trade-off between spectrum sensing and data transmission. In this paper, we show the relationship between spectrum sensing and data transmission according to the sensing period. We analyze and propose the new scheme to evaluate optimal sensing period.

Cherry Tomato Supplementation Reduces Cardiovascular Risk

  • Koh, Jong-Ho;Lim, Young-Hee;Hwang, Dahyun
    • Biomedical Science Letters
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    • v.23 no.4
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    • pp.321-326
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    • 2017
  • Tomatoes are rich in nutrients and have many beneficial advantages on human health. Four cherry tomato supplementation diets (CTSDs) were prepared from the juice and cake of fresh and processed (heat-treated) cherry tomatoes. Rats were fed CTSDs for 28 days and the changes in health indices in the serum were analyzed. CTSDs significantly decreased (P < 0.05) food efficiency ratio compared with the control. CTSD feeding significantly increased (P < 0.05) the high-density lipoprotein cholesterol level compared with the control, which resulted in a significant (P < 0.05) decrease in coronary artery risk index and atherogenic index. Furthermore, CTSD feeding increased serum serotonin level. These results indicate that CTSD shows antihyperlipidemic effect.