bluuebunny/crossref_metadata_2025_split huggingface dataset:
In‐Cell Characterization of the Stable Tyrosyl Radical in E. coli Ribonucleotide Reductase Using Advanced EPR Spectroscopy
Authors: Meichsner Shari L. , Kutin Yury , Kasanmascheff Müge 
Published: April 2021

AbstractThe E. coli ribonucleotide reductase (RNR), a paradigm for class Ia enzymes including human RNR, catalyzes the biosynthesis of DNA building blocks and requires a di‐iron tyrosyl radical (Y122.) cofactor for activity. The knowledge on the in vitro Y122. structure and its radical distribution within the β2 subunit has accumulated over the years; yet little information exists on the in vivo Y122.. Here, we characterize this essential radical in whole cells. Multi‐frequency EPR and electron‐nuclear double resonance (ENDOR) demonstrate that the structure and electrostatic environment of Y122. are identical under in vivo and in vitro conditions. Pulsed dipolar EPR experiments shed light on a distinct in vivo Y122. per β2 distribution, supporting the key role of Y. concentrations in regulating RNR activity. Additionally, we spectroscopically verify the generation of an unnatural amino acid radical, F3Y122., in whole cells, providing a crucial step towards unique insights into the RNR catalysis under physiological conditions.
Scaling and relative size of the human, nonhuman ape, and baboon calcaneus
Authors: Harper Christine M. , Ruff Christopher B. , Sylvester Adam D. 
Published: April 2021

AbstractAmong human and nonhuman apes, calcaneal morphology exhibits significant variation that has been related to locomotor behavior. Due to its role in weight‐bearing, however, both body size and locomotion may impact calcaneal morphology. Determining how calcaneal morphologies vary as a function of body size is thus vital to understanding calcaneal functional adaptation. Here, we study calcaneus allometry and relative size in humans (n = 120) and nonhuman primates (n = 278), analyzing these relationships in light of known locomotor behaviors. Twelve linear measures and three articular facet surface areas were collected on calcaneus surface models. Body mass was estimated using femoral head superoinferior breadth. Relationships between calcaneal dimensions and estimated body mass were analyzed across the sample using phylogenetic least squares regression analyses (PGLS). Differences between humans and pooled nonhuman primates were tested using RMA ANCOVAs. Among (and within) genera residual differences from both PGLS regressions and isometry were analyzed using ANOVAs with post hoc multiple comparison tests. The relationships between all but two calcaneus dimensions and estimated body mass exhibit phylogenetic signal at the smallest taxonomic scale. This signal disappears when reanalyzed at the genus level. Calcaneal morphology varies relative to both body size and locomotor behavior. Humans have larger calcanei for estimated body mass relative to nonhuman primates as a potential adaptation for bipedalism. More terrestrial taxa exhibit longer calcaneal tubers for body mass, increasing the triceps surae lever arm. Among nonhuman great apes, more arboreal taxa have larger cuboid facet surface areas for body mass, increasing calcaneocuboid mobility.
In vitro and in vivo evaluation of a water‐in‐oil microemulsion of platycodin D
Authors: Shen Jinyang , Zhu Yuexia , Zhou Bingxue , Kong Li , Jin Ye , Zhang Di , Cao Zhiling , Ji Jing , Li Jiaojiao 
Published: April 2021

AbstractPlatycodin D (PD) is the active metabolite of Platycodon grandiflorum. The main purpose of this study was to develop and evaluate a water‐in‐oil (W/O) microemulsion formulation of PD (PD‐ME). The PD‐ME was successfully prepared by the water titration method at K
m = 2, to draw the pseudoternary phase diagrams. Physical characterization including the particle size, pH, refractive index, average viscosity, and polydispersity index (PDI) was performed. The in vivo characteristics were evaluated by intestinal permeability and pharmacokinetic studies. The optimized microemulsion formulation consisted of 100 mg/ml PD aqueous solution, soybean phospholipids, ethanol, and oleic acid (27:39:19:15, w/w). The average viscosity, pH, droplet size, PDI, and zeta potential of the PD‐ME were 78.65 ± 0.13 cPa•s, 5.70 ± 0.05, 30.46 ± 0.20 nm, 0.33 ± 0.00, and −3.13 mV, respectively. The drug concentration of the PD‐ME was 26.3 ± 0.6 mg/ml. The PD‐ME showed significantly higher apparent permeability coefficients than PD (p < .01). The pharmacokinetic studies showed that the PD‐ME had significantly higher values of T
1/2 (2.26‐fold), AUC0–24h (area under the curve; 1.65‐fold), and MRT0–24h (1.58‐fold) than PD (p < .01). It can be seen that W/O ME presents a strategy with great promise for enhancing the intestinal permeability and better oral absorption of drugs with high polarity and poor permeability.
Sieving Effect for the Separation of C2H2/C2H4 in an Ultrastable Ultramicroporous Zinc‐Organic Framework
Authors: Chu Qianqian , Zhang Shihui , Li Xiuyuan , Guo Panyue , Fu Aiyun , Liu Bo , Wang Yao‐Yu 
Published: April 2021

AbstractThe separation of C2H2 from C2H4 is one of the most challenging tasks due to the similarity of their physical properties. In addition, green synthetic protocol and adsorbent's stability are also the major concerns during the separation. Herein, under hydrothermal green synthesis conditions, an ultrastable ultramicroporous Zn‐MOF was designed and synthesized with a high yield. The pore diameter of the Zn‐MOF is 3.6 Å, which lies in between the diameters of C2H2 (3.3 Å) and C2H4 (4.2 Å) molecules, leading to an efficient separation of the C2H2/C2H4 mixtures by the sieving effect. The practical separation performance of C2H2/C2H4 was confirmed by the dynamic breakthrough experiments. Moreover, the high stability enables the adsorption capacity of the Zn‐MOF to C2H2, which can be maintained under a wide range of pH (1–13). Molecular simulations were also performed to identify the different C2H2‐ and C2H4‐binding sites in Zn‐MOF.
Technical‐scale biophotovoltaics for long‐term photo‐current generation from Synechocystis sp. PCC6803
Authors: Lai Bin , Schneider Hans , Tschörtner Jenny , Schmid Andreas , Krömer Jens O. 
Published: April 2021

AbstractA carbon‐free energy supply is essential to sustain our future. Biophotovoltaics (BPV) provides a promising solution for hydrogen supply by directly coupling light‐driven water splitting to hydrogen formation using oxygenic photoautotrophic cyanobacteria. However, BPV is currently limited by its low photon‐to‐current efficiency, and current experimental setups at a miniaturized scale hinder the rational investigation of the process and thus system optimization. In this article, we developed and optimized a new technical‐scale (~250 ml working volume) BPV platform with defined and controllable operating parameters. Factors that interfered with reproducible and stable current output signals were identified and adapted. We found that the classical BG11 medium, used for the cultivation of cyanobacteria and also in many BPV studies, caused severe interferences in the bioelectrochemical experiments. An optimized nBG11 medium guaranteed a low and stable background current in the BPV reactor, regardless of the presence of light and/or mediators. As proof‐of‐principle, a very high long‐term light‐dependent current output (peak current of over 20 µA) was demonstrated in the new set‐up over 12 days with living Synechocystis sp. PCC6803 cells and validated with appropriate controls. These results report the first reliable BPV platform generating reproducible photocurrent while still allowing quantitative investigation, rational optimization, and scale‐up of BPV processes.
Molecular dynamics simulations and analysis for bioinformatics undergraduate students
Authors: Justino Gonçalo C. , Nascimento Catarina P. , Justino Marta C. 
Published: April 2021

AbstractA computational biochemistry laboratory, fitted for bioinformatics students, is presented. The molecular dynamics package GROMACS is used to prepare and simulate a solvated protein. Students analyze the trajectory with different available tools (GROMACS and VMD) to probe the structural stability of the protein during the simulation. Students are also required to make use of Python libraries and write their own code to probe non‐covalent interactions between the amino acid side chains. Based on these results, students characterize the system in a qualitatively approach but also assess the importance of each specific interaction through time. This work mobilizes biochemical concepts and programming skills, fostering critical thinking and group work and developing presenting skills.
Keep a journal for reflection and responsibility
Authors: Hodges Dawn Z. 
Published: April 2021

While scrolling through LinkedIn recently, I happened upon an article from Harvard Business Review titled “The More Senior Your Job Title, the More You Need to Keep a Journal.” Dan Ciampa wrote, “Journal entries should provide not only a record of what happened but how we reacted emotionally; writing it down brings a certain clarity that puts things in perspective.” He added, “A personal journal should be part of any leader's toolkit.”
Esterification of Succinic Acid Using Sulfated Zirconia Supported on SBA‐15
Authors: Aguzín Federico L. , Martínez María L. , Beltramone Andrea R. , Padró Cristina L. , Okulik Nora B. 
Published: April 2021

AbstractCatalytic esterification of succinic acid with ethanol to obtain diethyl succinate (DES), a nontoxic plasticizer, is reported. Three sulfated zirconias supported on SBA‐15 [SZ‐SBA‐15(X)] with Si/Zr molar ratios (X) of 10, 20, and 30 were synthesized and characterized. N2adsorption/desorption isotherms and X‐ray diffraction patterns evidenced preservation of the ordered mesoporous structure of the catalysts after incorporation of Zr. Yields of DES greater than 85 % were obtained at the final reaction time by using SZ‐SBA‐15(10) and SZ‐SBA‐15(20) catalysts, which were higher than those achieved with Amberlyst 36. Reuse of the SZ‐SBA‐15(20) catalyst showed that, even though the structure of the support was preserved, decreases in sulfur concentration and in the DES yield occurred.
Construction of a Poly(anthraquinone Sulfide)/Carbon Nanotube Composite with Enhanced Li‐ion Storage Capacity
Authors: Mao Wutao , Ding Yiming , Li Maolong , Ma Chao , Cao Zhixiang , He Chang , Bao Keyan , Qian Yitai 
Published: April 2021

AbstractQuinone compounds are among the most promising candidate organic materials for energy storage due to advantages such as their higher theoretical energy density. In the present paper, a one‐step condensation method is described for connecting anthraquinone units via thioether bonds to generate a poly(anthraquinone sulfide) (PAQS) material as a promising lithium energy‐storage system. Poly(anthraquinone sulfide)/carbon nanotube (PAQS/CNT) frameworks are then prepared via an in‐situ chemical solution method. The good electrochemical performance of the PAQS/CNT composite with 2 wt % carbon nanotubes is then demonstrated, with a significantly higher discharge specific capacity (187.2 mA h g−1) than that of a pure PAQS electrode (101.0 mA h g−1). Moreover, the specific capacity remains at 168.4 mA h g−1 after 200 cycles, with a retention rate of 90.0 %. It is confirmed that CNTs play a number of roles in the composite polymer material, such as stabilizing the material structure during battery charging and discharging, improving the electronic conductivity, and alleviating the dissolution of the components of the organic electrolyte.
Sandwich Structure of 3D Porous Carbon and Water‐Pillared V2O5 Nanosheets for Superior Zinc‐Ion Storage Properties
Authors: Shao Yalong , Zeng Jing , Li Junjie , Ren Honglin , Zhang Zhonghua , Liu Jing , Mao Changming , Guo Xiaosong , Li Guicun 
Published: April 2021

AbstractVanadium oxides are promising cathode materials for rechargeable aqueous zinc‐ion batteries (RAZIBs). However, the self‐agglomeration and poor ion/electron conductivity of vanadium oxides in the charge/discharge process usually lead to low capacity and capacity attenuation, which limits their commercial application. Herein, we report a facile and mass‐production method for fabricating 3D porous carbon/water‐pillared V2O5 nanosheet composites with sandwich structure (PC/V2O5 ⋅ nH2O), which can further reduce the preparation cost of vanadium‐oxide‐based cathodes. Moreover, the excellent structural characteristics of PC/V2O5 ⋅ nH2O not only effectively inhibits the aggregation and stacking of V2O5 ⋅ nH2O but also increases the contact area between the active substance and the electrolyte, which is conducive to the transport of zinc ions and improves the electrochemical performance of RAZIBs. The PC/V2O5 ⋅ nH2O cathode displays an excellent rate performance (325.3 mAh g−1 at high current density 20 A g−1), a high specific discharge capacity of 415.4 mAh g−1 at 0.5 A g−1, an outstanding cyclic stability, and capacity retention (after 1000 cycles the capacity retention rate about 97.1 %). Ex situ XRD patterns reveal that the charge/discharge process of the PC/V2O5 ⋅ nH2O electrode undergoes a reversible intercalation and conversion process. The method used in this work provides an idea for large‐scale synthesis of vanadium‐based cathode materials for multivalent batteries.
Facile Preparation of CuCo2S4/Cu7.2S4 Nanocomposites as High‐Performance Cathode Materials for Rechargeable Magnesium Batteries**
Authors: Zhang Qin , Hu Yaobo , Wang Jun , Dai Yuanxiao , Pan Fusheng 
Published: April 2021

AbstractRechargeable magnesium batteries (RMBs) have been considered a promising energy‐storage device due to their high energy density and high safety, but they still suffer from a lack of high‐rate performance and cycle performance of the cathode. Nanosized CuCo2S4/Cu7.2S4 composites have been synthesized for the first time by a facile solvothermal method. Herein, the magnesium ion storage behavior when applied in the cathode for RMBs is discussed. Electrochemical results demonstrated that the CuCo2S4/Cu7.2S4 composites exhibit a high initial discharge capacity of 256 mAh g−1 at 10 mA g−1 and 123 mAh g−1 at 300 mA g−1 at room temperature and an outstanding long‐term cyclic stability over 300 cycles at 300 mA g−1. Furthermore, the electrochemical storage mechanism demonstrated that the storage process of magnesium ion in the CuCo2S4/Cu7.2S4 cathode is mainly driven by strong pseudocapacitive effects.
Ruthenium‐Catalyzed Deuteration of Aromatic Carbonyl Compounds with a Catalytic Transient Directing Group
Authors: Kopf Sara , Ye Fei , Neumann Helfried , Beller Matthias 
Published: April 2021

AbstractA novel ruthenium‐catalyzed C−H activation methodology for hydrogen isotope exchange of aromatic carbonyl compounds is presented. In the presence of catalytic amounts of specific amine additives, a transient directing group is formed in situ, which directs selective deuteration. A high degree of deuteration is achieved for α‐carbonyl and aromatic ortho‐positions. In addition, appropriate choice of conditions allows for exclusive labeling of the α‐carbonyl position while a procedure for the preparation of merely ortho‐deuterated compounds is also reported. This methodology proceeds with good functional group tolerance and can be also applied for deuteration of pharmaceutical drugs. Mechanistic studies reveal a kinetic isotope effect of 2.2, showing that the C−H activation is likely the rate‐determining step of the catalytic cycle. Using deuterium oxide as a cheap and convenient source of deuterium, the methodology presents a cost‐efficient alternative to state‐of‐the‐art iridium‐catalyzed procedures.
Thiazolidinediones: An In–Depth Study of Their Synthesis and Application to Medicinal Chemistry in the Treatment of Diabetes Mellitus
Authors: Long Nathan , Le Gresley Adam , Wren Stephen P. 
Published: April 2021

Abstract2,4‐Thiazolidinedione (TZD) is a privileged and highly utilised scaffold for the development of pharmaceutically active compounds. This sulfur‐containing heterocycle is a versatile pharmacophore that confers a diverse range of pharmacological activities. TZD has been shown to exhibit biological action towards a vast range of targets interesting to medicinal chemists. In this review, we attempt to provide insight into both the historical conventional and the use of novel methodologies to synthesise the TZD core framework. Further to this, synthetic procedures utilised to substitute the TZD molecule at the activated methylene C5and N3position are reviewed. Finally, research into developing clinical agents, which act as modulators of peroxisome proliferator‐activated receptors gamma (PPARγ), protein tyrosine phosphatase 1B (PTP1B) and aldose reductase 2 (ALR2), are discussed. These are the three most targeted receptors for the treatment of diabetes mellitus (DM).
Tetrahydroquinoline/4,5‐Dihydroisoxazole Molecular Hybrids as Inhibitors of Breast Cancer Resistance Protein (BCRP/ABCG2)
Authors: Vesga Luis C. , Kronenberger Thales , Tonduru Arun Kumar , Kita Diogo Henrique , Zattoni Ingrid Fatima , Bernal Cristian Camilo , Bohórquez Arnold R. Romero , Mendez‐Sánchez Stelia Carolina , Ambudkar Suresh V. , Valdameri Glaucio , Poso Antti 
Published: April 2021

AbstractMultidrug resistance (MDR) is one of the major factors in the failure of many chemotherapy approaches. In cancer cells, MDR is mainly associated with the expression of ABC transporters such as P‐glycoprotein, MRP1 and ABCG2. Despite major efforts to develop new selective and potent inhibitors of ABC drug transporters, no ABCG2‐specific inhibitors for clinical use are yet available. Here, we report the evaluation of sixteen tetrahydroquinoline/4,5‐dihydroisoxazole derivatives as a new class of ABCG2 inhibitors. The affinity of the five best inhibitors was further investigated by the vanadate‐sensitive ATPase assay. Molecular modelling data, proposing a potential binding mode, suggest that they can inhibit the ABCG2 activity by binding on site S1, previously reported as inhibitors binding region, as well targeting site S2, a selective region for substrates, and by specifically interacting with residues Asn436, Gln398, and Leu555. Altogether, this study provided new insights into THQ/4,5‐dihydroisoxazole molecular hybrids, generating great potential for the development of novel most potent ABCG2 inhibitors.
On the Finite Time Blowup of the De Gregorio Model for the 3D Euler Equations
Authors: Chen Jiajie , Hou Thomas Y. , Huang De 
Published: April 2021

AbstractWe present a novel method of analysis and prove finite time asymptotically self‐similar blowup of the De Gregorio model [13, 14] for some smooth initial data on the real line with compact support. We also prove self‐similar blowup results for the generalized De Gregorio model [41] for the entire range of parameter on ℝ or for Hölder‐continuous initial data with compact support. Our strategy is to reformulate the problem of proving finite time asymptotically self‐similar singularity into the problem of establishing the nonlinear stability of an approximate self‐similar profile with a small residual error using the dynamic rescaling equation. We use the energy method with appropriate singular weight functions to extract the damping effect from the linearized operator around the approximate self‐similar profile and take into account cancellation among various nonlocal terms to establish stability analysis. We remark that our analysis does not rule out the possibility that the original De Gregorio model is well‐posed for smooth initial data on a circle. The method of analysis presented in this paper provides a promising new framework to analyze finite time singularity of nonlinear nonlocal systems of partial differential equations. © 2021 Wiley Periodicals LLC.
Can Counter‐Intuitive Halogen Bonding Be Coulombic?
Authors: Murray Jane S. , Politzer Peter 
Published: April 2021

AbstractWe use the term “counter‐intuitive” to describe an intermolecular interaction in which the electrostatic potentials of the interacting regions of the ground‐state molecules have the same sign, both positive or both negative. In the present work, we consider counter‐intuitive halogen bonding with nitrogen bases, in which both the halogen σ‐hole and the nitrogen lone pair have negative potentials on their molecular surfaces. We show that these interactions can be treated as Coulombic despite the apparent repulsion between the ground‐state molecules, provided that both electrostatics and polarization are explicitly taken into account. We demonstrate first that the energies of 20 counter‐intuitive interactions with four nitrogen bases can be expressed very well in terms of just two molecular properties: the electrostatic potential of the halogen σ‐hole and the average polarizability of the nitrogen base. Then we show that the same two properties can also represent the energies of an expanded data base that includes the 20 counter‐intuitive plus an additional 20 weak and moderately‐strong intuitive halogen bonding interactions (in which the σ‐hole potentials are now positive).
Cloning and functional analysis of LH2, a gene controlling late heading in rice
Authors: Dong Shiqing , Sun Dayun , Han Xiaokang , Zhu Yu , Niu Fuan , Liu Yang , Liu Shuang , Sun Xuejun , Ren Ding , Hu Zejun , Wang Ying , Yan Peiwen , Xin Xiaoyun , Yang Jinshui , Luo Xiaojin 
Published: April 2021

AbstractHeading date is an important agronomic trait in rice (Oryza sativa L.). We previously fine‐mapped two complementary genes, Late Heading Date 1 and Late Heading Date 2 (LH2), that control the late heading trait in rice. Here, we cloned and analyzed the function of LH2. LH2 was fine‐mapped to a 53‐kb genomic region. Sequencing analysis revealed that there were differences in the coding sequence of LOC_Os08g07740 between the varieties ‘Bo B’ and ‘Yuefeng B’. Therefore, LOC_Os08g07740 was identified as a candidate gene for LH2 and subsequently determined that LH2 is a Type 3 allele of Days To Heading 8. Transgenic plants of Yuefeng B carrying LH2 from Bo B significantly delayed the heading date under short‐day and long‐day conditions. A yeast two‐hybrid analysis revealed that LH2 physically interacted with Heme Activator Protein (HAP) 5A, ‐H, ‐I, ‐L, ‐K, and HAP5‐LIKE. The HAP5 domain of HAP5 family members has various functions. Further analysis revealed that LH2 represses photoperiodic flowering by controlling the expression of Early Heading Date 1, Heading date 3a, and Rice Flowering Locus T1 in rice.
Symmetrical and asymmetrical microstripline‐based transmit/receive switches for 7‐Tesla magnetic resonance imaging
Authors: Abuelhaija Ashraf , Saleh Gameel , Baldawi Tarik , Salama Sanaa 
Published: April 2021

SummaryThe transmit/receive (T/R) switch is an important device in magnetic resonance imaging scanners whenever T/R radio frequency coils are intended to be used. It is placed between transmit amplifiers and T/R radio frequency coils. The T/R switch adds loss to the radio frequency (RF) transmit chain, reducing the delivered power to the coil and increasing the noise figure of the receive chain. Therefore, T/R switches should be designed for as low insertion loss as possible. In addition, they need to handle high power in transmit. In this article, three T/R switches for 7‐Tesla magnetic resonance imaging scanners are designed using Eagle, and validated by simulation (HFSS & ANSYS) and measurement. Low reflection coefficients (< −20 dB), low insertion loss (≃0.3 dB), and high isolation (>40 dB) were demonstrated for the designed couplers. The fabricated microstripline‐based switches were more robust than a design utilizing commercial couplers in terms of heat dissipation, high power capabilities, and lower insertion loss.