In Silico Screening of Potential Inhibitors against dPLA2 from Named Chinese Herbs for Identification of Compounds with Antivenom Effects Due to Deinagkistrodon acutus Snake Bites

Phospholipase A2 (PLA2) is the key enzyme to the venom from Deinagkistrodon acutus which is one of the highly venomous snakes in China. In addition to being a catalyst for the hydrolysis of phospholipases A2 from snake venom, its well known that it possesses a broad spectrum of pharmacological activities, such as myotoxicity, neurotoxicity, cardiotoxicity, and hemolytic, anticoagulant and antiplatelet activities. However, snakebites are not efficiently treated by conventional serum therapy. Acute wounds can still cause poisoning and death. In order to find effective inhibitors of Deinagkistrodon venom acid phospholipase A2 (dPLA2), we obtained 385 compounds in 9 Chinese herbs from the TCMSP. These compounds were further performed to virtual screen using in silico tools like ADMET analysis, molecular docking and molecular dynamics (MD) simulation. After Pharmacokinetics analysis, we found 7 candidate compounds. Besides, analysis of small molecule interactions with dPLA2 confirmed that the amino acid residues HIS47 and GLY29 are key targets. Because they bind not only to the natural substrate phosphatidylcholine and compounds known for having inhibitory functions, but also for combining with potential antidote molecules in Chinese herbal medicine. This study is the first to report experience with virtual screening for possible inhibitor of dPLA2, such as the interaction spatial structure, binding energy and binding interaction analysis, these experiences not only provide reference for further experimental research, but also have a guideline for the study of drug molecular mechanism of action.

Low-loss chip-scale programmable silicon photonic processor

Chip-scale programmable optical signal processors are often used to flexibly manipulate the optical signals for satisfying the demands in various applications,such as lidar,radar,and artificial intelligence.Silicon photonics has unique advantages of ultra-high integration density as well as CMOS compatibility,and thus makes it possible to develop large-scale programmable optical signal processors.The challenge is the high silicon waveguides propagation losses and the high calibration complexity for all tuning elements due to the random phase errors.In this paper,we propose and demonstrate a programmable silicon photonic processor for the first time by introducing low-loss multimode photonic waveguide spirals and low-random-phase-error Mach-Zehnder switches.The present chip-scale programmable silicon photonic processor comprises a 1×4 variable power splitter based on cascaded Mach-Zehnder couplers(MZCs),four Ge/Si photodetectors,four channels of thermally-tunable optical delaylines.Each channel consists of a continuously-tuning phase shifter based on a waveguide spiral with a micro-heater and a digitally-tuning delayline realized with cascaded waveguide-spiral delaylines and MZSs for 5.68 ps time-delay step.Particularly,these waveguide spirals used here are designed to be as wide as 2μm,enabling an ultralow propagation loss of 0.28 dB/cm.Meanwhile,these MZCs and MZSs are designed with 2-μm-wide arm waveguides,and thus the random phase errors in the MZC/MZS arms are negligible,in which case the calibration for these MZSs/MZCs becomes easy and furthermore the power consumption for compensating the phase errors can be reduced greatly.Finally,this programmable silicon photonic processor is demonstrated successfully to verify a number of distinctively different functionalities,including tunable time-delay,microwave photonic beamforming,arbitrary optical signal filtering,and arbitrary waveform generation.

Porous polymer microsphere functionalized with benzimidazolium based ionic liquids as effective solid catalysts for esterification

To prepare polymer supported ionic liquids(PSILs)as effective catalysts for esterification,the free radical suspension copolymerization of vinylbenzyl chloride(VBC,monomer),styrene(St,monomer)and divinylbenzene(DVB,crosslinker)with the addition of n-heptane(porogen)was carried out for the fabrication of the porous polymer(PVD)microsphere as support,followed by the immobilization of sulfonic acid-functionalized ionic liquids by the successive treatment of benzimidazole(BIm),1,3-propane sultone and sulfuric acid(H2SO4)or trifluoromethanesulfonic acid(CF3SO3H).The effects of the compositions of DVB and n-heptane on the internal structure of the polymer supports were investigated,and it was found that the support with 40 wt%DVB and 60 wt%n-heptane(with relative to the monomer)could endow the final PSILs with the relatively optimal catalytic performance.The preliminary experiment in the batch reactor indicated that PSILs herein exhibited higher catalytic activities than commercial Amberlyst 46 resin for the esterification of propanoic acid(PROAc)with n-propanol(PROOH).Consequently,the optimal PSILs catalyst,PVD-[Bim-SO3H]HSO4,was selected for further study in the batch reactive distillation column because of low cost and its ease of preparation.The yield of propyl ropionate(PROPRO)could reach up to 97.78%at the optimized conditions of PROOH/PROAc molar ratio(2:1)and catalyst dosage(2.0 wt%).The investigation of the reaction kinetic manifested that the calculated results of second order pseudo-homogeneous kinetic model were in good agreement with experimental values.The pre-exponential factor and activation energy were 4.12×107 L·mol-1·min-1 and 60.57 k J·mol-1,respectively.It is worth noting that the PSILs catalyst could be simply recovered and reused with relatively satisfactory decrease in the catalytic activity,which made it an environmental friendly and promising catalyst in the industrial application.

Ultrahigh-Q silicon racetrack resonators

An ultrahigh-Q silicon racetrack resonator is proposed and demonstrated with uniform multimode silicon photonic waveguides.It consists of two multimode straight waveguides connected by two multimode waveguide bends(MWBs).In particular,the MWBs are based on modified Euler curves,and a bent directional coupler is used to achieve the selective mode coupling for the fundamental mode and not exciting the higher-order mode in the racetrack.In this way,the fundamental mode is excited and propagates in the multimode racetrack resonator with ultralow loss and low intermode coupling.Meanwhile,it helps achieve a compact 180°bend to make a compact resonator with a maximized free spectral range(FSR).In this paper,for the chosen 1.6μm wide silicon photonic waveguide,the effective radius Reffof the designed 180°bend is as small as 29μm.The corresponding FSR is about 0.9 nm when choosing 260μm long straight waveguides in the racetrack.The present high-Q resonator is realized with a simple standard single-etching process provided by a multiproject wafer foundry.The fabricated device,which has a measured intrinsic Q-factor as high as 2.3×10~6,is the smallest silicon resonator with a>106Q-factor.

Wavelength-selective 2 × 2 optical switch based on a Ge2Sb2Te5-assisted microring

A novel wavelength-selective 2×2 optical switch based on a Ge2Sb2Te5(GST)-assisted microring-resonator(MRR)is proposed.The present GST-assisted MRR consists of two access optical waveguides and an MRR coupled with a bent GST-loaded silicon photonic waveguide.The 2×2 optical switch is switched ON or OFF by modifying the GST state to be crystalline or amorphous.In particular,the microring waveguide and the bent GST-loaded waveguide are designed to satisfy the phase-matching condition when the GST is crystalline.As a result,the MRR becomes highly lossy and the resonance peak is depressed significantly.On the other hand,when it is off,there is little coupling due to the significant phase mismatching.Consequently,one has a low-loss transmission at the drop port for the resonance wavelength.In this paper,the simulation using the three-dimensional finite-difference method shows that the extinction ratio of the designed photonic switch is^20 d B at the resonance wavelength,while the excess losses at the through port and drop port are 0.9 d B and 2 d B.In particular,the resonance wavelength changes little between the ON and OFF states,which makes it suitable for multichannel wavelength-division-multiplexing systems.

Ultralow-loss compact silicon photonic waveguide spirals and delay lines

Low-loss and compact optical waveguides are key for realizing various photonic integrated circuits with long onchip delay lines,such as tunable optical delay lines,optical coherence tomography,and optical gyroscopes.In this paper,a low-loss and compact silicon photonic waveguide spiral is proposed by introducing broadened Archimedean spiral waveguides with a tapered Euler S-bend.A 100-cm-long waveguide spiral is realized with a minimal bending radius as small as 10 μm by using a standard 220-nm-thick silicon-on-insulator foundry process,and the measured propagation loss is as low as 0.28 dB/cm.Furthermore,the present waveguide spirals are used to realize a 10-bit tunable optical delay line,which has a footprint as small as 2.2 mm × 5.9 mm and a dynamic range of 5120 ps with a fine resolution of 10 ps.

Sub-nanosecond-speed frequency-reconfigurable photonic radio frequency switch using a silicon modulator

Radio frequency(RF)switches are essential for implementing routing of RF signals.However,the increasing demand for RF signal frequency and bandwidth is posing a challenge of switching speed to the conventional solutions,i.e,the capability of operating at a sub-.nanosecond speed or faster.In addition,signal frequency reconfigurability is also a desirable feature to facilitate new innovations of flexible system functions.Utilizing microwave photonics as an alter-native path,we present here a photonic implementation of an RF switch providing not only the capability of switching at a sub-nanosecond speed but also options of frequency doubling of the input RF signals,allowing for flexible output waveforms.The core device is a traveling wave silicon modulator with a device size of0.2 mm × 1.8 mm and a modu-lation bandwidth of 10 GHz.Using microwave frequencies,i.e.,15 GHz and 20 GHz,as two simultaneous RF input signals,we experimentally demonstrated their amplitude and frequency switching as well as that of the doubled frequencies,ie,30 GHz and 40 GHz,at a switching frequency of 5 GHz.The results of this work point to a solution for creating high speed RF switches with high compactness and flexibility.

Silicon nonlinear switch as a conditional circulator for monostatic LiDAR systems

All-optical silicon-photonics-based LiDAR systems allow for desirable features in scanning resolution and speed,as well as leverage other advantages such as size, weight, and cost. Implementing optical circulators in silicon photonics enables bidirectional use of the light path for both transmitters and receivers, which simplifies the system configuration and thereby promises low system cost. In this work, to the best of our knowledge, we present the first experimental verification of all-passive silicon photonics conditional circulators for monostatic LiDAR systems using a nonlinear switch. The proposed silicon nonlinear interferometer is realized by controlling signal power distribution with power-splitting circuits, allowing the LiDAR transmitter and receiver to share the same optical path. Unlike the traditional concept requiring a permanent magnet, the present device is implemented by using common silicon photonic waveguides and a standard foundry-compatible fabrication process. With several additional phase shifters, the demonstrated device exhibits considerable flexibility using a single chip, which can be more attractive for integration with photodetector arrays in LiDAR systems.