USP25 deubiquitinating enzyme is a key member of the ubiquitin system, which acts as a positive regulator of the Wnt/β-catenin signaling by promoting the deubiquitination and stabilization of tankyrases. USP25 is characterized by the presence of a long insertion in the middle of the conserved catalytic domain. The crystal structure of USP25 displays an unexpected homotetrameric quaternary assembly that is directly involved in the inhibition of its enzymatic activity. The tetramer is assembled by the association of two dimers and includes contacts between the coiled-coil insertion domain and the ubiquitin-binding pocket at the catalytic domain, revealing a distinctive autoinhibitory mechanism. Biochemical and kinetic assays with dimer, tetramer and truncation constructs of USP25 support this mechanism, displaying higher catalytic activity in the dimer assembly. Moreover, the high stabilization of tankyrases in cultured cells by ectopic expression of a constitutive dimer of USP25 supports a biological relevance of this tetramerization/inhibition mechanism.

Background: USP28 is a deubiquitinating enzyme implicated in the DNA damage response, Myc stabilization, and cancer progression. Results: USP28 activity is regulated by SUMO conjugation on the N-terminal region. Conclusion:The N-terminal ubiquitin-binding domains of USP28 are not required for polyubiquitin processing. Significance: Cross-talk exists between SUMO and ubiquitin in the regulation of USP28 enzymatic activity.

Modeling the electrophoretic mobility of peptides is examined in this study using a "coarse grained" bead model, or B model for short 8 and also a simpler "effective sphere" (ES) model. A comparison between the B and ES models is carried out for peptide models covering a broad range of ionic strength, peptide charge, and peptide length. At ionic strengths lower than approximately 0.013 M, the B and ES models agree to within a few percent. The ES model is much simpler than the B model and is of particular value in certain applications such as complex formation between peptide and other species in the BGE. The mobility behavior of oligoglycine in a borate buffer at high pH can be accounted for when complex formation is included in modeling.

(-)-Epingaione demonstrated broad-spectrum inhibitory activity against plant pathogenic fungi and is promising for exploitation as a fungicide.

Co-crystal technology has effectively improved the safety of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12hexaazaisowurtzitane (CL20) and retained high detonation velocity, detonation pressure and other properties of CL20. To study why thermal sensitivity of CL20/1,3-dinitrobenzene (DNB) co-crystal can be effectively reduced, simulations of the pyrolysis process of CL20/DNB co-crystal, CL20/TNT co-crystal, CL20 crystal and DNB crystal system were made with ReaxFF/lg force field reactive molecular dynamics in this paper. This paper provides from atomic level detailed information on thermal decomposition processes of CL20, DNB, CL20/DNB co-crystal and CL20/TNT co-crystal such as reaction pathway, contributing to a better understanding of differences between co-crystal and pure crystal. The results show that CL20/DNB co-crystal has lower thermal sensitivity than CL20 and CL20/TNT co-crystal, but has higher thermal sensitivity than DNB, which is consistent with experimental data. Besides, the initial reaction pathways of CL20 and CL20/DNB were found, which reveals the reasons why co-crystal can effectively reduce CL20 thermal sensitivity. CL20 and CL20/DNB have similar initial reaction pathways: N-NO 2 bond of CL20 molecules breaks, working as a dominant role in the initial stage of thermal decomposition under the condition of different temperatures, followed by cage skeleton structure breaking reaction. We found two reasons for the decrease rate of CL20 in CL20/DNB co-crystal decomposition: (A) The huge number of DNB molecules in the initial reaction stage prevents effective collision between CL20 and the intermediate reactants, thus lowering the speed of CL20 thermal decomposition. (B) Part of DNB molecules react with CL20 molecules and the intermediate products, producing C 6 H 4 N 3 O 6 , C 6 H 4 N 4 O 8 and C 10 H 10 N 14 O 16 etc., which decrease concentration of CL20. Both are explanations from microscopic mechanism on why the thermal sensitivity of CL20/DNB co-crystal is lower than that of CL20 crystal. In addition, CL20/DNB co-crystal and CL20 have similar main reactants, such as NO 2 , NO 3 , N 2 , N 2 O 2 , HNO, H 2 O, CO 2 , and HONO etc. Through the analysis of the reaction kinetics, we obtain activation barrier of CL20 system and CL20/DNB system. This study confirms the fact that co-crystallization is an effective way to decrease the thermal sensitivity for CL20 while retaining high detonation performance.

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For plasma source, the extraction of negative ions is quite different from that of positive ions. To understand the effect of extraction field on plasma, the time-dependent behavior of negative hydrogen ion extraction from a negative ion source has been studied by particle-in-cell simulation in the collisionless limit. The simulations have shown that, due to the difference in dynamics between electrons and ions, the imbalance of the numbers of charged particles occurs in the source, results in the broadening of plasma sheath and the great increase of plasma potential. The resultant high sheath field and the ambipolar electric field in plasma make the negatively charged particles congregate inside the sheath and move toward the extraction outlet. The emission area of negative ions is much smaller than that of the extraction aperture, which is in sharp contrast to the case of positive ion extraction.

To study the mechanical damage characteristics of layered composite rocks, sandstones, and mudstones of deep tight reservoirs were used as the research objects, and layered composite class rocks were prepared by similar material model tests. Uniaxial compression tests were conducted and supplemented with AE (Acoustic Emission) system and DIC (Digital Image Correlation) system to obtain the physical and mechanical parameters such as strength and elastic modulus of the layered composite rocks. The corresponding law of AE ringing count and rock damage evolution was studied and the damage process of layered composite rock under uniaxial loading was divided into three stages: initial damage, stable damage development, and damage acceleration. Analysis of strain cloud diagrams of the DIC system revealed that the deformation characteristics of the layered composite rock under uniaxial were mainly tensile-shear-slip damage. Based on the internal damage evolution characteristics of AE and the surface damage evolution characteristics of DIC, a damage constitutive model of layered composite rocks based on the dual damage factor characterization was established, which reasonably revealed the damage evolution mechanism of internal structure development and external crack germination, extension and penetration of layered composite rocks under uniaxial compression.