G protein-coupled receptors (GPCRs) are the largest class of cell surface drug targets. Advances in stabilization of GPCR:transducer complexes, together with improvements in cryoelectron microscopy ...(cryo-EM) have recently been applied to structure-assisted drug design for GPCR agonists. Nonetheless, limitations in the commercial application of these approaches, including the use of nanobody 35 (Nb35) to aid complex stabilization and the high cost of 300 kV imaging, have restricted broad application of cryo-EM in drug discovery. Here, using the PF 06882961-bound GLP-1R as exemplar, we validated the formation of stable complexes with a modified Gs protein in the absence of Nb35. In parallel, we compare 200 versus 300 kV image acquisition using a Falcon 4 or K3 direct electron detector. Moreover, the 200 kV Glacios-Falcon 4 yielded a 3.2 Å map with clear density for bound drug and multiple structurally ordered waters. Our work paves the way for broader commercial application of cryo-EM for GPCR drug discovery.
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•High-resolution imaging of GPCRs using non-proprietary technologies•3.2 Å structure of a GPCR using a 200 kV microscope•Imaging of small-molecule agonist class B GPCR with no stabilizing nanobodies
Traditionally, G protein-coupled receptors (GPCRs) need to be biochemically stabilized to be studied by cryo-EM. We show that it is possible to obtain high-quality 3D reconstructions without the need for a stabilizing nanobody. We also show that excellent imaging results can be obtained on both 200 and 300 kV microscopes.
This article presents a method for real-time simultaneous measurements of the temperature and soot volume fraction distribution of volatile matter flames, forming during combustion of biomass ...pellets. This method uses flame radiation spectra, captured by a spectrometer, and images, captured by a digital camera, as inputs during combustion of three different types of biomass pellets (pine wood, rice straw, and corn straw). The pellets were ignited and burned in the post-combustion zone of methane gas at 1300 K. The radiation spectrum of the flame in the 500–800 nm wavelength band was selected for spectral analysis, combined with a spectral emissivity model based on polynomial fitting. The flame emissivity was measured at the response wavelengths of a dual band-pass filter (centered at 615 and 517 nm) fitted on the camera, and the resulting emissivity ratio showed the degree of departure from the gray radiation model. The measured emissivity ratio approached unity as the combustion intensity increased. The emissivity ratio of the spectrometer measurement was used to correct the flame temperature measurement obtained by the image method. Upon correction, the maximum relative error of the image temperature measurement was determined to be 2.7% by comparison to thermocouple readings. The experimental results showed that the maximum flame temperatures of pine wood, rice straw, and corn straw pellets were remarkably similar at 1876 ± 2 K. Moreover, the flame burnout durations and the peak soot volume fractions were both positively correlated with the volatile content of biomass pellets; the value of the latter was 1.19 ± 3 ppm. The experimental results measured in this article can provide data for models of the soot generation mechanism of biomass pellet combustion in industrial furnaces.
Direct detector device (DDD) cameras have revolutionized electron cryomicroscopy (cryoEM) with their high detective quantum efficiency (DQE) and output of movie data. A high ratio of camera frame ...rate (frames per second) to camera exposure rate (electrons per pixel per second) allows electron counting, which further improves the DQE and enables the recording of super-resolution information. Movie output also allows the correction of specimen movement and compensation for radiation damage. However, these movies come at the cost of producing large volumes of data. It is common practice to sum groups of successive camera frames to reduce the final frame rate, and therefore the file size, to one suitable for storage and image processing. This reduction in the temporal resolution of the camera requires decisions to be made during data acquisition that may result in the loss of information that could have been advantageous during image analysis. Here, experimental analysis of a new electron-event representation (EER) data format for electron-counting DDD movies is presented, which is enabled by new hardware developed by Thermo Fisher Scientific for their Falcon DDD cameras. This format enables the recording of DDD movies at the raw camera frame rate without sacrificing either spatial or temporal resolution. Experimental data demonstrate that the method retains super-resolution information and allows the correction of specimen movement at the physical frame rate of the camera while maintaining manageable file sizes. The EER format will enable the development of new methods that can utilize the full spatial and temporal resolution of DDD cameras.
This paper aims to investigate the effects of graphene oxide (GO) on the microstructure and micromechanical properties of ultra-high performance concrete (UHPC) matrix and interfacial transition zone ...(ITZ) around the embedded steel fiber, and to reveal the working mechanism of GO, so as to fully understand the mesoscopic and macroscopic mechanical behaviors of GO reinforced UHPC. Mercury intrusion porosimetry (MIP) and backscattered electron microscopy (BSEM) were used to systematically study the microstructure evolution, and nanoindentation test was used to quantitatively characterize the microscale fracture toughness of UHPC matrix and ITZ. The results showed that GO induced more calcium-silicate-hydrate generation, which significantly reduced the porosity of the ITZ between steel fiber and matrix from 7.5-13.4% to 5.3%–10.5%, and promoted the homogenization of the microstructure. Due to the decrease of porosity and the bridge effect of GO nanosheets, the microscale fracture toughness in ITZ increases by 24.9% from 0.994 MPa m1/2 to 1.241 MPa m1/2 at the critical dosage of 0.04% GO, which is conducive to the improvement of the interface bonding between steel fibers and matrix, and thus increasing the macroscopic flexural strength of straight steel fiber UHPC and hooked-end fiber UHPC by 14.7% and 13.9% respectively.
•Both GO and GO-nanoSiO2 improves the fracture property of cementitious materials and GO-nanoSiO2 is more effective.•GO-nanoSiO2 improves the roughness of mortar fracture surface, changes the ...propagation mode of cracks.•NanoSiO2 on GO surface has pozzolanic activity and forms a covalent interlock between cement matrix and GO.
This study aims to improve the fracture properties of cementitious materials by adding graphene oxide (GO) and graphene oxide–silica nanocomposites (GO-nanoSiO2). The pristine GO was coated with nano-silica to form GO-nanoSiO2 composites. Based on the three-point bending test, the fracture toughness and fracture energy of cementitious materials were calculated to provide comprehensive fracture mechanics characterization. The fracture surface morphology and the crack development in mortar were detected by ultra-depth microscopy and scanning electron microscopy. The results demonstrate that the addition of GO-nanoSiO2 is more beneficial to improve the fracture properties of cementitious materials than pristine GO and the amount of nano-silica grafted on GO surface affects its enhancement effect. The initial fracture toughness, unstable fracture toughness and fracture energy of mortar reinforced by GO-nanoSiO2 (0.05 wt% GO and the mass ratio of nano-SiO2/GO is 2.8) are increased by 92.2%, 64.7% and 77.5%, respectively. GO-nanoSiO2 improves the roughness of mortar fracture surface, changes the propagation mode of cracks, and makes the crack propagate along a more tortuous path which contributes to energy dissipation.
•The combination of GO and steel fiber makes UHPC have the best fracture property.•GO improves the pull-out property of steel fiber by reinforcing the UHPC matrix.•The prediction model of UHPC ...fracture energy based on micromechanics is established.
This paper aims to achieve multi-scale crack control of concrete by using graphene oxide (GO) and macroscopic steel fiber in combination, and to reveal the multi-scale collaborative reinforcement mechanism of GO and steel fiber. A three-point bending fracture mechanics test was employed to analyze the macroscopic fracture properties of ultra-high performance concrete (UHPC) reinforced by GO, and a single fiber pull-out test was utilized to assess the impact of GO on the fiber–matrix interface properties. The results showed that 0.04% GO reinforced UHPC had the best fracture property, and steel fiber and GO showed good synergistic crack control effect. GO directly acted on controlling the cracking of concrete matrix at the nanoscale, thus improving the fracture energy of UHPC matrix by 14% from 73.08 N/mm to 83.39 N/mm. This micro-scale matrix reinforcement provided by GO further improved the pull-out property of steel fibers, and the pull-out energy dissipation of straight steel fibers and hook-end fibers was increased by 43.7% and 31.5%. A micromechanical prediction model for fracture energy of straight steel fiber UHPC was established, which could construct the quantitative relationship between UHPC fracture energy and micromechanical parameters. The model showed that the initial fiber–matrix bond strength (τ0) and slip hardening coefficient (k0) had a powerful influence on the UHPC fracture energy.
•0.05 wt% GO-nanoSiO2 improves the mechanical properties and chloride penetration resistance of mortar most effectively.•GO-nanoSiO2 reduces the total porosity of mortar and optimizes the pore ...structure.•GO-nanoSiO2 decreases the porosity and Ca(OH)2 enrichment in ITZ between aggregate and matrix and makes the microstructure of ITZ more uniform.
The purpose of this work is to study the effect of graphene oxide-silica nanocomposites on the mechanical properties, transport properties and microstructure of mortar, to reveal the working mechanism of GO-nanoSiO2 to improve the properties of mortar, so as to fully understand the mechanical and physical behavior of GO-nanoSiO2 reinforced mortar. The macroscopic test results showed that adding 0.05 wt% GO could improve the compressive strength, fracture toughness and chloride penetration resistance of mortar most effectively. The compressive strength, initial fracture toughness and unstable fracture toughness increased by 15.1%, 92.2%, and 64.7%, and the non-steady state chloride migration coefficients decreased by 49.6%. The microstructure of mortar was studied by MIP, SEM and multifractal analysis. The results showed that the addition of GO-nanoSiO2 reduces the total porosity and optimizes the pore structure of mortar, resulting in the reduction of large pores, the improvement of the homogeneity of pore distribution, and the formation of pores with poor pore connectivity, which is conducive to improving the impermeability of mortar. In the interface transition zone between aggregate and matrix, the addition of GO-nanoSiO2 decreases the porosity and Ca(OH)2 enrichment. The decrease of ITZ porosity and the presence of GO-nanoSiO2 nanosheets in ITZ can inhibit the crack propagation, thus contributing to the improvement of macroscopic fracture properties of mortar.
•An experimental design was used to investigate the effects of different torrefaction conditions on the properties of biomass.•Two spectrometers were simultaneously used to capture high SNR signals ...of continuous spectrum and characteristic spectrum.•In-situ detection of the temperature and K release concentration of torrefied biomass pellet combustion was achieved.•Changes in combustion characteristics and K release characteristics of torrefied biomass were evaluated.
The orthogonal experiment designed in this paper investigated the effect of changes in experimental parameters such as biomass species, torrefaction temperature, torrefaction time, torrefaction oxygen concentration on the physicochemical properties and combustion characteristics of the torrefaction products. Two optical fiber spectrometers were used to capture the spontaneous emission spectra of the combustion flame of compressed pellets of torrefied biomass, and the in-situ measurement of pellet combustion temperature and K release concentration at high heating rate was realized by multi-spectral analysis algorithm. The experimental results indicate that for biomass, torrefaction will lead to a decrease of volatile and moisture content and an increase of fixed carbon and ash content in components, a decrease of O and H and an increase of C content in elements, a certain loss of biomass quality, an increase of high heat value, and each indicator move closer to coal. The effects of various experimental parameters on the volatile content, mass yield, high heat value increase rate and energy yield in biomass torrefaction products have similar laws, i.e., biomass species / torrefaction oxygen concentration > torrefaction temperature > torrefaction time. The mild torrefaction product pellets have a shorter ignition delay, increased volatile combustion flame height and peak temperature, longer volatile and char combustion duration, but lower peak char combustion temperature, among which the selected torrefaction products of rice straw and pine wood showed an increase in peak temperature of 0.56 % (11 K) and 0.61 % (12 K) for the volatile stage respectively, and a decrease of and 1.29 % (20 K) and 1.29 % (21 K) for the char stage respectively. In addition, the peak K release concentration during combustion of the mild torrefaction product pellets was reduced, among which the peak K release concentrations during the volatile and char stage were reduced by 43.22 % (3.89 ppm) and 52.93 % (51.55 ppm) of the rice straw torrefaction product respectively, and by 73.14 % (1.28 ppm) and 62.08 % (15.01 ppm) for the pine wood torrefaction product respectively. Biomass torrefaction products have fuel properties closer to coal, less K released from the combustion process, which have the potential to become an alternative to coal.
Kanglaite (KLT) injection, a kind of Chinese medicine, is considered a promising complementary therapeutic option for malignant cancer treatment. This study aimed to systematically investigate the ...efficacy and safety of the combination of KLT injection and radiochemotherapy for the treatment of advanced pancreatic cancer (PC).
Studies were identified by searching Cochrane Library, Web of Science, PubMed, Embase, China National Knowledge Infrastructure (CNKI), Chinese Biological Medicine Database (CBM), Wanfang database and Chinese Scientific Journal Database (VIP) before October 2018. The primary reported outcomes including efficacy, quality of life (QoL), and adverse events were systematically evaluated.
Data from 16 trials with 960 patients with advanced PC were included. Compared with radiochemotherapy alone, the combination of KLT injection and radiochemotherapy significantly improved the 1-year overall survival (OS, odds ratio OR = 2.58 95% CI: 1.12-5.93 P = .03), overall response (ORR, OR = 2.16 95% CI: 1.58-2.94 P <.00001) and disease control rates (DCR, OR = 2.50 95% CI: 1.84-3.38 P <.00001). The QoL of patients, who received a combination of radiochemotherapy and KLT injection, also improved compared with radiochemotherapy treatment alone as indicated by the increased quality of life improved rate (QIR, OR = 3.68 95%CI: 2.36-5.75 P <.00001), pain relief rate (PRR, OR = 3.70 95% CI: 2.23-6.14 P <.00001) and weight gain rate (WGR, OR = 3.69 95% CI: 2.22-6.13 P <.00001). Adverse events related to radiochemotherapy including gastrointestinal side effects, nephrotoxicity, leukopenia, thrombocytopenia, and myelosuppression were alleviated (P <.05) when KLT was injected to patients with PC.
Evidence from the Meta-analysis suggested that the combinational treatment of radiochemotherapy and KLT injection is more effective in advanced PC treatment than radiochemotherapy alone. Additionally, the combination therapy improved QoL of the patients. KLT injection can alleviate the adverse effects associated with the radiochemotherapy.
•A measurement method of K concentration is proposed based on the emission spectrum.•The temperature affected the radiation intensity of the K characteristic spectra.•The K concentration of biomass ...pellets was measured at different combustion stages.•The peak K release concentration of the rice straw was 110.43 ppm.
Here, a calibration method using the K concentration, temperature and the characteristic spectral line radiation intensity in flame is described. In addition, a radiation function model between these three variables, Iλ766T,CK=0.821·Ib(λ766,T)·CK, was established. A Y-type optical fiber was used to connect the spectral signals from the same direction to two spectrometers. The continuous spectra in the 500–800 nm band were used for multi-spectral temperature measurements. The combination of the measured temperature and the K characteristic spectral line radiation intensity at 766 nm was used for measurements of K concentration. The temperature and equivalent ratio of the heating atmosphere were 1300 K (±20 K) and 0.786, respectively. Compared with rice straw pellet, pine wood pellet had a lower K concentration and higher combustion temperature during the entire combustion process. The peak K release concentrations of the pine wood pellet and the rice straw pellet during the volatile combustion stage were 2.09 ppm and 10.03 ppm, respectively, and the peak flame temperatures were 1774 K and 1756 K, respectively. In the char combustion stage, the peak K release concentrations were 27.83 ppm and 110.43 ppm, respectively, and the peak surface temperatures were 1287 K and 1143 K, respectively. The established function model for measuring K concentration is also applicable to the combustion diagnosis of other K-rich fuels.
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