Search

Amino acids have a multi-billion-dollar market with rising demand, prompting the development of high-performance microbial factories. However, a general screening strategy applicable to all proteinogenic and non-proteinogenic amino acids is still lacking. Modification of the critical structure of tRNA could decrease the aminoacylation level of tRNA catalyzed by aminoacyl-tRNA synthetases. Involved in a two-substrate sequential reaction, amino acids with increased concentration could elevate the reduced aminoacylation rate caused by specific tRNA modification. Here, we developed a selection system for overproducers of specific amino acids using corresponding engineered tRNAs and reporter genes. As a proof-of-concept, overproducers of five amino acids such as L-tryptophan were screened out by growth-based and/or fluorescence-activated cell sorting (FACS)-based screening from random mutation libraries ofEscherichia coliandCorynebacterium glutamicum, respectively. This study provided a universal strategy that could be applied to screen overproducers of proteinogenic and non-proteinogenic amino acids in amber-stop-codon-recoded or non-recoded hosts.

The anthocyanin-rich litchi shell extract (LE) was mixed with the matrix to prepare active/intelligent food packaging composite films. The microstructure and properties of composite films were characterized. The results showed that the composite films incorporated with LE had texture-oriented layered, compact, uniform cross-sections. The composite films with LE showed different degrees of red. The composite films had similar water vapor transmission rates (1.62-1.65 × 10

Extracellular vesicles (EVs) derived from living cells play important roles in donor cell-induced recipient tissue regeneration. Although numerous studies have found that cells undergo apoptosis after implantation in an ischemic-hypoxic environment, the roles played by the EVs released by apoptotic cells are largely unknown. In this study, we obtained apoptotic vesicles (apoVs) derived from human deciduous pulp stem cells and explored their effects on the dental pulp regeneration process. Our work showed that apoVs were ingested by endothelial cells (ECs) and elevated the expression of angiogenesis-related genes, leading to pulp revascularization and tissue regeneration. Furthermore, we found that, at the molecular level, apoV-carried mitochondrial Tu translation elongation factor was transported and regulated the angiogenic activation of ECs via the transcription factor EB-autophagy pathway. In a beagle model of dental pulp regeneration in situ, apoVs recruited endogenous ECs and facilitated the formation of dental-pulp-like tissue rich in blood vessels. These findings revealed the significance of apoptosis in tissue regeneration and demonstrated the potential of using apoVs to promote angiogenesis in clinical applications.

A paralytic shellfish toxin binding protein (PST-BP) was extracted and purified from the viscera of oyster (Crassostrea hongkongensis) that accumulates paralytic shellfish toxin (PST), and the amino acid sequence of the protein was detected via HPLC-MS-MS. The structure of the PST-BP was built by homology modeling, and the interaction between PST and PST-BP was studied using molecular docking. The results showed that the purity of PST-BP was more than 99.8% after the purification. The PST-BP carried a molecular weight of 33.5 kDa and sequence alignment revealed its high sequence similarities with glyceraldehyde-3-phosphate-dehydrogenase (GAPDH). It has been shown that 99.9% of the amino acid residues in the PST-BP homology model are within a reasonable range, which exceeds the 90% threshold requirement for residuals in high-quality model structures. The molecular docking results revealed that Arg, Asp, Lys, Ala, Ser, Gln, Gly, Trp, Asn, Met, and Pro were identified as the major interacting amino acids residues between PST-BP and PST.

Unified pixel-based (PB) beamforming has been implemented for ultrasound imaging, offering significant enhancements in lateral resolution compared to the conventional dynamic focusing. However, it still suffers from clutter and off-axis artifacts, limiting the contrast resolution. This paper proposes an efficient method to improve image quality by integrating filtered delay multiply and sum (F-DMAS) into the framework. This hybrid strategy incorporates the spatial coherence of the received data into the beamforming process to improve contrast resolution and clutter rejection in the generated image. We also integrate a Wiener filter to suppress the spatiotemporal spreading using signals echoed from a single scatterer at the transmit focus as a kernel for the deconvolution. The Wiener filter is applied to the received waveforms before performing the hybrid strategy. The Wiener filter is shown to reduce interference due to the interaction between the excitation pulse and the transfer functions of the transducer elements, thus benefiting the axial resolution of the generated images. We validate the proposed method and compare it with other beamforming strategies through a series of experiments, including simulation, phantom, and in vivo studies. The results show that our approach can substantially improve both spatial resolution and contrast over the unified PB algorithm, while still maintaining the good features of this beamformer. The simplicity and good performance of our method show its potential for use in clinical applications.

Identification of the factors controlling the migration of hexavalent chromium (Cr (VI)) in soil can provide valuable information for pollution control and risk assessment. In this study, we assessed the processes of transportation and migration of Cr (VI) in soil by batch and column experiments. Breakthrough curves were used to examine the mobility of Cr (VI) in soil columns. Most of them could be described by a typical S-shaped curve. The Yoon–Nelson model and Thomas model were applied to predict the behavior of Cr (VI) in soil and obtained parameters to characterize the rate and capacity of adsorption. It was observed that all obtained parameters changed along with soil properties. Moreover, stepwise multiple regression and grey correlation analysis were used to determine the main control factors by evaluating the relationship between soil properties and dynamic or static parameters. The results showed Fe oxide content was the key factor no matter in static or dynamic adsorption while soil texture had a great influence on the transportation of Cr (VI) in soil columns. Also, in the actual situation, the external input condition should not be ignored. Our research provides meaningful information for authorities to develop better soil management and remediation strategies.

Streptomycin (STR) plays an essential role in bacterial infection treatments. Selectivity and sensitivity of photoelectrochemical (PEC) sensors are the two most important parameters, which can be measured using the photosensitivity of its active material. We prepared a novel PEC sensor to detect STR using Bi/BiVO4/LDH (layered double hydroxides) heterostructures as an active material, which is photoactive in the visible light wavelength range. The simultaneous presence of LDH and Bi/BiVO4 enhanced the material photocurrent response, which was linear to the STR concentrations in the 0.01–500 nmol/L range. The STR detection limit by this sensor was 0.0042 nmol/L. Our novel PEC-based sensing strategy includes using an ultra-sensitive and highly selective sensor for STR detection. Additionally, the two-pot synthesis of Bi/BiVO4/LDH developed in this work is environmentally friendly.