Search

The proteolytic active sites of the 26S proteasome are sequestered within the catalytic chamber of its 20S core particle (CP). Access to this chamber is through a narrow channel defined by the outer α subunits. Free 20S CP is found in a latent state in which the N-termini of neighboring α subunits form a gate blocking access to the channel. Entry of substrates can be facilitated by the attachment of the activators or regulatory particles, which can rearrange the blocking α subunit N-terminal residues. In order to determine the specific physiological role of individual elements working in concert within the gate, we constructed a set of truncations or single-site mutations in each of the participating α N-terminal tails. We report herein that whereas only a few N-termini are important for maintaining a closed gate, all seven N-termini participate in the open gate. Specifically, an invariant tyrosine (Y) in each subunit forms a hydrogen bond with a conserved aspartate (D) in the N-terminal tail of its counterclockwise neighbor, with the exception of the α1-α2 pair leaving a gap in the ring circumference. A third residue (X) of this YD(X) motif aligns the open channel; specifically, the phenylalanine (F) at this position of the α2 subunit comes in direct contact with the translocating substrate. Consequently, deletion of this α2 N-terminal tail slows down proteolysis despite the appearance of an open gate state. We conclude that the YD(X) motif in N-terminal tail of α subunits plays an important role in gating the proteasome and in processing the substrate.

The development of environmentally friendly, simple process and low cost synthesis methods for preparing graphene nanosheets (GNs) has attracted global interest. In this work, a simple and efficient method to synthesize GNs deriving from coal-tar pitch has been proposed from both experimental and theoretical point of views. The XRD, TEM and Raman results demonstrate that precursor Al4C3 could provide a growth environment for the final product of GNs. Innovatively, we have unraveled the microscopic origin for the decomposition of Al4C3 based on density functional theory calculations. It is highlighted that the surface energies and the analysis of elastic constants indicate the fact that the chemical etching process in Al4C3 can happen, which is similar to the exfoliation of well-known transition metal carbides MXenes. Furthermore, different bond breaking mechanisms have been found in Al4C3 at applied tensile and shear strains from the electron localization functions and stress–strain results. Our study not only offers an efficient method to synthesize GNs, but also to unravel the microscopic mechanism of fabrication by theoretical calculations.

With the increasingly close relationship between renewable energy and the distribution network, this article proposes a reactive power distribution network based on a series of problems such as reactive power fluctuations, network loss increases, and voltage fluctuations in the distribution network. The optimization method is to establish a distribution network reactive power optimization model with the goal of minimizing the new function formed by the entire system loss and the absolute value of the voltage fluctuation; then, the algorithm is optimized by the method proposed in this paper, and then the optimized algorithm is used to The model is solved; finally, the IEEE-33 node system with some nodes connected to renewable energy is used for simulation verification. The simulation results show that the model proposed in the article can greatly reduce the network loss, the total voltage fluctuation is smaller, the compensation amount of the reactive power compensation device is less, and the construction of related devices can be reduced, thereby reducing the investment cost of the distribution network.

This paper proposes a research method for the location and capacity planning of regional substations. This method mainly studies and analyzes the active distribution network space based on load forecasting to complete the location and capacity analysis of regional substations. Combining the GIS information system and the power sensor network, based on the spatial load prediction results, and combined with the regional distributed power planning results, the location and capacity planning of the regional substations are carried out, and finally based on the location selection and capacity results, the power supply range of the substation and Economic calculation indicators have formed a set of technologically advanced, comprehensive and practical planning schemes, which can not only meet the needs of the distribution network at all levels in Xiongan New District for substation location and capacity, but also can be extended to urban areas of six cities, such as A, It is used in Class B areas to provide data support and scientific basis for the location and capacity of substations in the power grid, realize accurate planning, and assist relevant technical personnel in making decisions.

Aiming at the problem that it is difficult to consider the interaction between distributed power sources and network structures of active power distribution systems in the process of collaborative planning, a mathematical model and solution algorithm considering the balance of multi-agent interests and alternate optimization of planning and operation are proposed. Firstly, a three-tier optimization framework and mathematical model are established that aim at the optimal cost-benefit of distributed power sources and distribution networks, and embedded demand response and operation strategies; secondly, a simplified network structure based on the principle of topology equivalence is proposed. Based on the method, combined with the in-depth analysis of the topological structure change characteristics during the grid generation process, a rapid generation method of single-contact network based on the breaking method is proposed, and the encoding/decoding scheme of the particle swarm optimization algorithm combined with it is formulated; again, Based on the characteristics of network load and user demand response willingness, the dynamic time-of-use electricity price optimization method and operation strategy of active distribution network are proposed, and the source network collaborative planning and solving process with built-in refined operation is established; finally, it is verified by an example The rationality and effectiveness of the method are described.

Currently, building energy consumption accounts for 30-45% of global energy consumption, and the energy flexibility of the building provides it with controllable potential. In view of the lack of existing research on the overall controllable ability of building energy system from upper energy supply system. This paper defines controllable ability of building energy system, and proposes a unified dynamic evaluation model. Firstly, the impact of each influencing factor on the controllable ability is quantified, including virtual energy storage, electrical appliances, HVAC system, CCHP system, and occupants’ demand response. Secondly, analytical method and optimization method are used to evaluate the controllable ability. Then, based on the division of initial states, a sequential recurrence method is proposed to realize the dynamic evaluation of controllable ability. Finally, a practical case is used to verify the effectiveness and practicability of this method.