Halide methyltransferases (HMTs) provide an effective way to regenerate S‐adenosyl methionine (SAM) from S‐adenosyl homocysteine and reactive electrophiles, such as methyl iodide (MeI) and methyl ...toluene sulfonate (MeOTs). As compared with MeI, the cost‐effective unnatural substrate MeOTs can be accessed directly from cheap and abundant alcohols, but shows only limited reactivity in SAM production. In this study, we developed a dynamic cross‐correlation network analysis (DCCNA) strategy for quickly identifying hot spots influencing the catalytic efficiency of the enzyme, and applied it to the evolution of HMT from Paraburkholderia xenovorans. Finally, the optimal mutant, M4 (V55T/C125S/L127T/L129P), exhibited remarkable improvement, with a specific activity of 4.08 U/mg towards MeOTs, representing an 82‐fold increase as compared to the wild‐type (WT) enzyme. Notably, M4 also demonstrated a positive impact on the catalytic ability with other methyl donors. The structural mechanism behind the enhanced enzyme activity was uncovered by molecular dynamics simulations. Our work not only contributes a promising biocatalyst for the regeneration of SAM, but also offers a strategy for efficient enzyme engineering.
S‐Adenosylmethionine assumes a crucial role in biocatalytic alkylation. To improve the catalytic ability of BxHMT towards methyl toluene sulfonate, a strategy named dynamic cross‐correlation network analysis (DCCNA) was proposed for the identification of potential mutation sites, both distal and proximal. Experimental results proved the efficiency of the approach, which is expected to be a useful tool for other enzyme engineering studies.
The small field inflation (SFI) of Coleman-Weinberg (CW) type suffers from precise tuning of the initial inflaton field value to be away from the true vacuum one. We propose a dynamical trapping ...mechanism to solve this problem: an ultra-supercooling caused by an almost scale-invariant CW potential traps the inflaton at the false vacuum, far away from the true vacuum dominantly created by the quantum scale anomaly, and allows the inflaton to dynamically start the slow-roll down due to a classical explicit-scale breaking effect. To be concrete, we employ a successful CW-SFI model and show that the proposed mechanism works consistently with the observed bounds on the inflation parameters. The proposed new mechanism thus provides new insights for developing small field inflation models.
A RhIII‐catalyzed intramolecular oxidative cross‐coupling between double bonds for the synthesis of macrolides is described. Under the optimized reaction conditions, macrocycles containing a diene ...moiety can be formed in reasonable yields and with excellent chemo‐ and stereoselectivity. This method provides an efficient approach to synthesize macrocyclic compounds containing a 1,3‐conjugated diene structure.
Two pair: A RhIII‐catalyzed intramolecular oxidative cross‐coupling between double bonds for the synthesis of macrolides is described. Under the optimized conditions, macrocycles containing a diene moiety can be formed in reasonable yields and with excellent chemo‐ and stereoselectivity. This provides efficient access to macrocyclic compounds containing 1,3‐conjugated dienes.
The PyProcar Python package plots the band structure and the Fermi surface as a function of site and/or s,p,d,f - projected wavefunctions obtained for each k-point in the Brillouin zone and band in ...an electronic structure calculation. This can be performed on top of any electronic structure code, as long as the band and projection information is written in the PROCAR format, as done by the VASP and ABINIT codes. PyProcar can be easily modified to read other formats as well. This package is particularly suitable for understanding atomic effects into the band structure, Fermi surface, spin texture, etc. PyProcar can be conveniently used in a command line mode, where each one of the parameters define a plot property. In the case of Fermi surfaces, the package is able to plot the surface with colors depending on other properties such as the electron velocity or spin projection. The mesh used to calculate the property does not need to be the same as the one used to obtain the Fermi surface. A file with a specific property evaluated for each k-point in a k−mesh and for each band can be used to project other properties such as electron–phonon mean path, Fermi velocity, electron effective mass, etc. Another existing feature refers to the band unfolding of supercell calculations into predefined unit cells.
Program Title: PyProcar
Program Files doi:http://dx.doi.org/10.17632/d4rrfy3dy4.1
Licensing provisions: GPLv3
Programming language: Python
Nature of problem: To automate, simplify and serialize the analysis of band structure and Fermi surface, especially for high throughput calculations.
Solution method: Implementation of a Python library able to handle, combine, parse, extract, plot and even repair data from density functional calculations. PyProcar uses color maps on the band structures or Fermi surfaces to give a simple representation of the relevant characteristics of the electronic structure.
Additional comments: Features: PyProcar can produce high-quality figures of band structures and Fermi surfaces (2D and 3D), projection of atomic orbitals, atoms, and/or spin components.
Restrictions: Only the VASP package is currently fully supported, the latest version of Abinit is partially supported (it will be fully supported in the Abinit versions 9.x). The PROCAR file format can easily be implemented within any DFT code.
Although microstrip reflectarrays/transmitarrays have been extensively studied in the past decades, most previous designs were confined to monofunctional operations based on either transmission or ...reflection. In this communication, we propose a scheme to design multifunctional arrays that can simultaneously exhibit the functionalities of a reflectarray and a transmitarray on the basis of the appealing feature of a polarizer we discovered (i.e., constant phase difference between its cross-polarization transmission and copolarization reflection within a broadband). To demonstrate the proposed scheme, we designed and fabricated a multifunctional device comprising a 15 × 15 array of twisted complementary dual-split ring resonators, each carefully designed to exhibit the desired transmission phase satisfying a parabolic distribution. Feeding the device by a Vivaldi antenna at its focus, we numerically and experimentally demonstrated that our system functioned as a directive emitter working in a transmission/reflection mode for cross-polarization/copolarization radiation at low/high frequencies, and it can radiate directively in both directions with different polarizations at intermediate frequencies. The half-power beamwidth of the array antenna was ~15°, which is 40° narrower than that of a bare Vivaldi antenna. Moreover, the gain was higher than 13 dB in all cases studied, which is at least 7 dB higher than that of the Vivaldi antenna.
Achieving flexible and highly directive emissions toward pre‐designed directions has intrigued long‐held interest in both science and engineering community, but most available efforts suffer the ...issues of bulky size, limited functionalities, and low efficiency. Here, we propose a general strategy to efficiently and flexibly control the emission beams with dual functionalities realized independently by orthogonal excitations. To overcome the polarization cross‐talking, a novel planar multi‐mode anisotropic meta‐atom is designed by incorporating the screening effect of a surrounding wire loop. As the result, we can design the polarization‐dependent phase profile under certain polarization, without worrying about their influences on the other polarization. As an illustration, two proof‐of‐concept metasurfaces are actualized at microwave frequencies, of which one combines the functionalities of focused‐beam and large‐angle multibeam emissions while another hybrids the functionalities of beam‐steering and small‐angle multibeam emissions. Theoretical, full‐wave simulation, and experimental results are in excellent agreement with each other, which collectively demonstrate the desired performances of our bifunctional devices. Our proposed strategy paves the way to realize high‐performance multifunctional optical devices with high integration and complex wavefront manipulations.
Flexible control on directive emissions toward pre‐designed directions has attracted long‐term interest, but available devices suffer from bulky size, limited functionalities, and low efficiencies. Here, a novel anisotropic meta‐atom exhibiting low polarization cross‐talking was proposed, based on which high‐efficiency metasurfaces with arbitrary polarization‐dependent phase profiles can be easily designed to realize desired beam‐control functionalities. The strategy paves the way to realize high‐performance multifunctional optical devices with high integration.
The Global Positioning System (GPS) is widely used in outdoor environmental positioning. However, GPS cannot support indoor positioning because there is no signal for positioning in an indoor ...environment. Nowadays, there are many situations which require indoor positioning, such as searching for a book in a library, looking for luggage in an airport, emergence navigation for fire alarms, robot location, etc. Many technologies, such as ultrasonic, sensors, Bluetooth, WiFi, magnetic field, Radio Frequency Identification (RFID), etc., are used to perform indoor positioning. Compared with other technologies, RFID used in indoor positioning is more cost and energy efficient. The Traditional RFID indoor positioning algorithm LANDMARC utilizes a Received Signal Strength (RSS) indicator to track objects. However, the RSS value is easily affected by environmental noise and other interference. In this paper, our purpose is to reduce the location fluctuation and error caused by multipath and environmental interference in LANDMARC. We propose a novel indoor positioning algorithm based on Bayesian probability and
-Nearest Neighbor (BKNN). The experimental results show that the Gaussian filter can filter some abnormal RSS values. The proposed BKNN algorithm has the smallest location error compared with the Gaussian-based algorithm, LANDMARC and an improved KNN algorithm. The average error in location estimation is about 15 cm using our method.
In this article, by deliberately controlling multiple resistive electric and magnetic resonances in terms of dispersion and dissipation, a low-profile, wideband, microwave metamaterial absorber with ...wide-angle and polarization-independent responses is proposed. The proposed absorber comprises a planar array with resistance-loaded metallic cross patterns, and a vertical periodic crossed mesh array with resistance-loaded metallic ring patterns. The vertical periodic crossed mesh array was inserted between the planar array and the metal ground to improve the wide-angle polarization-independent absorption. The involved dispersion-engineered design strategy for angular- and polarization-insensitive responses is described with numerical evidences and electromagnetic response behaviors. A proof-of-concept absorber was fabricated and measured for verification. At quasi-normal incidence, the measured bandwidth characterized by more than 90% absorption was 2.11-3.89 GHz, i.e., a fractional bandwidth (FBW) of 59.3%. At the incident angle of 50°, the FBW of the absorption larger than 90% was 48.6%. The absorber was thin with a thickness of 13 mm, corresponding to 0.09λ 0 at the lowest operating frequency. The numerical and experimental results demonstrated that our proposed strategy provides an effective way to achieve wide-angle and polarization-independent responses in a broadband; these responses are very promising for most strategic applications.
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