73,560 research outputs found
CHO microRNA engineering is growing up : recent successes and future challenges
Full text linkmicroRNAs with their ability to regulate complex pathways that control cellular behavior and phenotype have been proposed as potential targets for cell engineering in the context of optimization of biopharmaceutical production cell lines, specifically of Chinese Hamster Ovary cells. However, until recently, research was limited by a lack of genomic sequence information on this industrially important cell line. With the publication of the genomic sequence and other relevant data sets for CHO cells since 2011, the doors have been opened for an improved understanding of CHO cell physiology and for the development of the necessary tools for novel engineering strategies. In the present review we discuss both knowledge on the regulatory mechanisms of microRNAs obtained from other biological models and proof of concepts already performed on CHO cells, thus providing an outlook of potential applications of microRNA engineering in production cell lines
Site-selective enzymatic C‒H amidation for synthesis of diverse lactams
Full text linkPlease note that this work has been retracted by the authors.After publication of the Report “Site-selective enzymatic C‒H amidation for synthesis of diverse lactams” in Science (1, also linked in metadata), efforts to reproduce the work showed that the enzymes do not catalyze the reactions with the activities and selectivities claimed. Careful examination of the first author’s lab notebook then revealed missing contemporaneous entries and raw data for key experiments. The authors therefore have retracted the article from Science and are now retracting the preprint from ChemRxiv. The original paper can be accessed by selecting “Version 1” of the preprint below, or by accessing https://doi.org/10.26434/chemrxiv.7711418.v1. Inha Cho, Zhi-Jun Jia, Frances H. Arnold*Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA.*Corresponding author. Email: [email protected]. I. Cho, Z.-J. Jia, F. H. Arnold, Science 364, 575 (2019). DOI: 10.1126/science.aaw9068*******************************************************************************************Directed evolution of cytochrome P450 enzymes fine-tunes site selectivity of new-to-nature C‒H amidation for modular, sustainable and scalable preparation of enantio-enriched β-, γ- and δ-lactams.</p
Development and growth of the foot lumbricalis muscle: a histological study using human foetuses
No full textBackground: Our group has shown early development of the hand lumbricalis and hypothesized that, at midterm, the lumbricalis (LU) bundles flexor tendons to provide a configuration of "one tendon per one finger" (Cho K.H. Folia Morphol. 2012; 71, 3: 154-163). However, the study concentrated on the hand and contained no sections of near-term foetuses.
Materials and methods: The present examination of paraffin-embedded tangential sections along the planta from 25 embryos and foetuses at 6-40 weeks (15-320 mm crown-rump length) demonstrated that, at 8 weeks, the initial foot LU appeared in the proximal side of the common tendinous plate of all five deep tendons.
Results: After midterm, a drastic three-phase change occurred at the muscle origin: 1) the LU originated from each of the flexor digitorum longus tendon (FDLT), but abundant tenocyte candidates separated the muscle fibre from the tendon collagen bundle; 2) the LU arose from the covering fascia depending on increased thickness of the muscle; and 3) the LU muscle fibres intermingled with tendon collagen bundles and partly surrounded the tendon. Simultaneously, a dividing site of the FDLT migrated distally to accelerate the changes at the LU origin. These phases did not always correspond to the size of foetus after 30 weeks.
Conclusions: Consequently, in contrast to the hand LU, the delayed changes in the foot were characterised by involvement of the LU origin into a single common part of the FDLT. The quadratus plantae muscle fibres did not attach to the LU at any phase, and connected with the fourth and fifth toe tendons.Depto. de Anatomía y EmbriologíaFac. de MedicinaTRUEpu
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
The ALMA-PILS survey: First detection of the unsaturated 3-carbon molecules Propenal (CHCHO) and Propylene (CH) towards IRAS 162932422 B
Full text linkAccepted for publication in A&A. 24 pages, 17 figuresInternational audienceComplex organic molecules with three carbon atoms are found in the earliest stages of star formation. In particular, propenal (CHCHO) is a species of interest due to its implication in the formation of more complex species and even biotic molecules. This study aims to search for the presence of CHCHO and other three-carbon species such as propylene (CH) in the hot corino region of the low-mass protostellar binary IRAS 16293--2422 to understand their formation pathways. We use ALMA observations in Band 6 and 7 from various surveys to search for the presence of CH and CHCHO towards the protostar IRAS 16293--2422 B (IRAS 16293B). We report the detection of both CH and CHCHO towards IRAS 16293B, however, no unblended lines were found towards the other component of the binary system, IRAS 16293A. We derive column density upper limits for CH, HCCCHO, n-CHOH, i-CHOH, CO, and cis-HC(O)CHO towards IRAS 16293B. We then use a three-phase chemical model to simulate the formation of these species in a typical prestellar environment followed by its hydrodynamical collapse until the birth of the central protostar. Different formation paths, such as successive hydrogenation and radical-radical additions on grain surfaces, are tested and compared to the observational results. The simulations reproduce the abundances within one order of magnitude from those observed towards IRAS 16293B, with the best agreement found for a rate of cm s for the gas-phase reaction C + O C + CO. Successive hydrogenations of C, HC(O)CHO, and CHOCHO on grain surfaces are a major and crucial formation route of complex organics molecules, whereas both successive hydrogenation pathways and radical-radical addition reactions contribute to the formation of CHCHO
Negative Transconductance Heterojunction Organic Transistors and their Application to Full-Swing Ternary Circuits
No full textMultivalued logic (MVL) computing could provide bit density beyond that of Boolean logic. Unlike conventional transistors, heterojunction transistors (H-TRs) exhibit negative transconductance (NTC) regions. Using the NTC characteristics of H-TRs, ternary inverters have recently been demonstrated. However, they have shown incomplete inverter characteristics; the output voltage (V-OUT) does not fully swing from V-DD to G(ND). A new H-TR device structure that consists of a dinaphtho[2,3-b:2 ',3 '-f]thieno[3,2-b]thiophene (DNTT) layer stacked on a PTCDI-C13 layer is presented. Due to the continuous DNTT layer from source to drain, the proposed device exhibits novel switching behavior: p-type off/p-type subthreshold region /NTC/ p-type on. As a result, it has a very high on/off current ratio (approximate to 10(5)) and exhibits NTC behavior. It is also demonstrated that an array of 36 of these H-TRs have 100% yield, a uniform on/off current ratio, and uniform NTC characteristics. Furthermore, the proposed ternary inverter exhibits full V-DD-to-G(ND) swing of V-OUT with three distinct logic states. The proposed transistors and inverters exhibit hysteresis-free operation due to the use of a hydrophobic gate dielectric and encapsulating layers. Based on this, the transient operation of a ternary inverter circuit is demonstrated for the first time.11Nsciescopu
Formation of two isomeric C3HO radicals from charged precursors in the gas phase. Potential interstellar molecules
No full textTheoretical calculations of the C3HO potential surface at the CCSD(T)/aug-cc-pVDZ//B3LYP/6-31G* level indicate that the three radicals HCCCO, CCCHO, and (cyclo-C₃H)dO are stable, with HCCCO being the most stable of the three. A fourth isomer, CCHCO, is unstable with respect to cyclization to (cyclo-C₃H)dO. Two isomers have been prepared by neutralization of charged precursors, formed as follows: (i) HCCCO, by HCtCsC(O)-⁺O(H)(Me) → HC₃O+ + MeOH, and (ii) C₂CHO, by (a) Me₃SiC≡C-CHO + HO⁻ → -C≡C-CHO + Me₃SiOH and (b) -C≡C-CH(OH)-C≡CH → ⁻C≡C-CHO + C²H². A comparison of the CR and ⁻NR⁺ spectra of ⁻C₂CHO indicate that C₂CHO is (partially) rearranging to an isomer that shows significant formation of CO°⁺ in the ⁻NR⁺ spectrum of the anion. Ab initio calculations indicate that HCCCO is the product of the isomerism and that a proportion of these isomerized neutrals dissociate to CO and C₂H. The neutral HCCCO may be formed by (i) synchronous rearrangement of C₂CHO and/or (ii) stepwise rearrangement of C₂CHO through (cyclo-C₃H)=O. The second of these processes should have the higher rate, as it has the lower barrier in the rate-determining step and the higher Arrhenius pre-exponential A factor.Salvatore Peppe, Stephen J. Blanksby, Suresh Dua, and John H. Bowi
Scoliosis : density-equalizing mapping and scientometric analysis
No full textBackground: Publications related to scoliosis have increased enormously. A differentiation between publications of major and minor importance has become difficult even for experts. Scientometric data on developments and tendencies in scoliosis research has not been available to date. The aim of the current study was to evaluate the scientific efforts of scoliosis research both quantitatively and qualitatively.
Methods: Large-scale data analysis, density-equalizing algorithms and scientometric methods were used to evaluate both the quantity and quality of research achievements of scientists studying scoliosis. Density-equalizing algorithms were applied to data retrieved from ISI-Web.
Results: From 1904 to 2007, 8,186 items pertaining to scoliosis were published and included in the database. The studies were published in 76 countries: the USA, the U.K. and Canada being the most productive centers. The Washington University (St. Louis, Missouri) was identified as the most prolific institution during that period, and orthopedics represented by far the most productive medical discipline. "BRADFORD, DS" is the most productive author (146 items), and "DANSEREAU, J" is the author with the highest scientific impact (h-index of 27).
Conclusion: Our results suggest that currently established measures of research output (i.e. impact factor, h-index) should be evaluated critically because phenomena, such as self-citation and co-authorship, distort the results and limit the value of the conclusions that may be drawn from these measures. Qualitative statements are just tractable by the comparison of the parameters with respect to multiple linkages. In order to obtain more objective evaluation tools, new measurements need to be developed
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