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关键词： Cytochrome c   Protein dynamics   Conformationally-gated electron transfer   Alkaline conformational transition   Apoptosis  

摘要： Cytochrome c (Cytc) contains two Ω-loops (C, residues 40–57 and D, residues 70–85) that control access of Cytc to alternate conformers needed to convert it from an electron transfer (ET) protein to an enzyme with peroxidase activity. As a peroxidase, Cytc oxygenates the mitochondrial lipid cardiolipin, which is an early signal in apoptosis. We probe the role of Pro76, a highly conserved residue in Ω-loop D, in controlling the access to alternate conformers of Cytc. We introduce histidines into Ω-loop D as specific probes of the alkaline conformational transition. We replaced Pro76 with His in the presence of a K72A mutation (A72H76 variant). Variants with K73H and P76G mutations (A72H73G76) and a K79A mutation added (A72H73G76A79) were also prepared. pH titrations monitored in the visible region show that, unlike the previously studied K73H variant, the native state (Met80 ligation) of Cytc is not populated between pH 2 and 11 for the A72H73G76 and A72H73G76A79 variants, indicating that the P76G mutation strongly destabilizes the native conformer. The A72H76 variant fully populates the native conformer near pH 5. GdnHCl unfolding studies and characterization of the alkaline transition by pH jump and gated ET kinetic studies were used to construct an energy landscape for the A72H76 variant. Comparison to other Ω-loop D histidine variants shows that the P76H mutation strongly destabilizes the native state and that Pro76 contributes to a native-like transition state. Both observations indicate that Pro76 is critical for controlling access to alternate conformers needed for peroxidase activity.

关键词： Secant varieties   Segre-Veronese varieties   Non-defectivity  

摘要： We prove that for any $m\ge 3$, $n\gg m^3$, all secant varieties of the Segre-Veronese variety ${\mathbb{P}}^m\times {\mathbb{P}}^n$ have the expected dimension. This was already proved by Abo and Brambilla in the subabundant case, hence we focus on the superabundant case. We generalize an approach due to Brambilla and Ottaviani into a construction we call the inductant. With a combinatorial investigation of these constructions, the proof of non-defectivity reduces to checking a finite collection of base cases, which we verify using a computer-assisted proof.

关键词： APE1/Ref-1   Carotid artery ligation   KLF4   Oxidative stress   Phenotypic switching   Vascular smooth muscle cell  

摘要： APE1/Ref-1, a multifunctional protein with redox activity, plays a pivotal role in maintaining cellular redox homeostasis and regulating gene expression. This study explored the role of APE1/Ref-1 deficiency on vascular smooth muscle cell (VSMC) phenotypic switching and its underlying mechanisms. Aorta with heterozygous APE1/Ref-1 deficiency (APE1/Ref-1^+/−) exhibited increased oxidative stress and impaired antioxidant defenses, as indicated by elevated reactive oxygen species (ROS) levels, significant 8-hydroxy-2′-deoxyguanosine (8-OHdG) accumulation and reduced expression of antioxidant enzymes. APE1/Ref-1^+/− VSMCs showed a significant reduction in contractile markers (SM22α and α-SMA), alongside an increase in Kruppel-like factor 4 (KLF4) and the proliferative marker PCNA. Treatment with hydrogen peroxide (H₂O₂) increased KLF4 expression and decreased contractile marker expression in VSMC. Furthermore, KLF4 knockdown restored the expression of contractile markers in VSMC. Chemical inhibition of KLF4 using kenpaullone also reversed the downregulation of contractile markers in APE1/Ref-1^+/− VSMCs. Overexpression of wild-type APE1/Ref-1, but not a redox-deficient mutant, rescued contractile marker expression and reduced KLF4 levels. In vivo, APE1/Ref-1^+/− mice displayed enhanced neointimal formation after carotid artery ligation. These findings suggest that APE1/Ref-1 deficiency promotes VSMC phenotypic switching and pathological vascular remodeling via oxidative stress-mediated KLF4 upregulation, and suggesting the critical role of APE1/Ref-1's redox function in vascular homeostasis.

关键词： Diels-Alder reaction   (E)-1,1,1,4,4,4-hexafluoro-2-butene   (Z)-1,1,1,4,4,4-hexafluoro-2-butene   Furan   2,3-Dimethyl-buta-1,3-diene   2-Methyl-buta-1,3-diene   Cyclohexane-1,3-diene  

摘要： The stereochemistry of the Diels-Alder reactions between (E)- and (Z)-1,1,1,4,4,4-hexafluoro-2-butene, and various dienes such as furan, 2,3-dimethyl-buta-1,3-diene, 2-methyl-buta-1,3-diene, and cyclohexa-1,3-diene, was investigated. Conducting these reactions at 100-140 °C in a solvent-free environment within an autoclave facilitated the synthesis of adducts in moderate yields, preserving the geometry of trifluoromethyl groups according to the Diels-Alder stereochemistry rules.

关键词： Backward evolution equations   Controllability   Fixed point theorem   Fractional derivative   Measure of non-compactness  

摘要： This paper investigates the approximate and exact controllability of a class of fractional backward evolution equations with order $1<\alpha <2$ in Hilbert spaces. First, by employing the Tikhonov-type regularization method to construct an approximate control function, we establish sufficient conditions for the approximate controllability of the system via Schauder${}^{\prime }$s fixed point theorem. Subsequently, the exact controllability of the system is systematically studied under two distinct cases: the compact semigroup case and the noncompact semigroup case. In particular, for the noncompact case, the controllability results are derived by utilizing the Mönch${}^{\prime }$s fixed point theorem combined with the technique of measures of non-compactness. Finally, an example is provided to verify the validity of the proposed theoretical results.

关键词： TASK-1   Cellular stress   Protein kinase C   Dynamin  

摘要： TASK-1 channel is important for regulating membrane potential. However, its response to pathological conditions remains unknown. In this study, we investigated the effects of hypoxia on the recombinant TASK-1 channel localization at the surface of HEK293T cells. The hypoxic condition was induced via sodium cyanide (NaCN) treatment. Exposure to NaCN led to a significant decrease in TASK-1 levels at the cell surface. This reduction was blocked by pre-exposure to a selective protein kinase C (PKC) inhibitor bisindolylmaleimide. Additional experiments demonstrated that blocking dynamin function or depleting cellular cholesterol prevented TASK-1 from the reduction at the cell surface. Fluorescence microscopic analysis further showed a selective reduction in cell surface wild type TASK-1 under hypoxic conditions, while double-leucine mutant TASK-1 remained unchanged. These results reveal a novel mechanism by which TASK-1 channel localization is modulated by chemical hypoxia, highlighting the importance of PKC, dynamin, and cholesterol in regulating TASK-1 trafficking.

关键词： Human mesenchymal stem cells (MSCs)   Bone marrow MSCs (BMMSCs)   Placental MSCs (PMSCs)   3D spheroid   Immunomodulation   Intercellular adhesion molecule-1 (ICAM-1)   Whole transcriptome profiling  

摘要： Three-dimensional (3D) in vitro culture systems may better mimic in vivo physiological conditions, and are easily accessible methods to improve therapeutic effectiveness of human mesenchymal stem cells (MSCs), which with its many sources appear to harbor clinically relevant functional differences. We therefore investigated the impact and elucidated the mechanism(s) of 3D culture on the immunomodulatory capacity of two commonly used MSC sources, bone marrow (BM) and placental (P). In 3D conditions, PMSCs (PMSC 3D) form larger spheroids than BMMSCs (BMMSC 3D), with whole transcriptome profiling revealing significant enrichment of cell adhesion and immunomodulatory pathways. qPCR and functional validation demonstrated the highest expression of numerous key immunomodulatory factors and strongest capacity to inhibit T cell proliferation with PMSC 3D. Bioinformatics analyses predicted Intercellular Adhesion Molecule 1 (ICAM-1) as crucial for both PMSC 3D spheroid formation and enhanced immunomodulatory capacity, which was validated with flow cytometric analyses and further delineated with single-cell RNA sequencing data. To assess mechanistic involvement, we performed knockdown of ICAM-1 which significantly reduced PMSC 3D spheroid size as well as both in vitro and in vivo immunomodulatory capacity. These findings demonstrate that 3D culture significantly enhances the immunomodulatory potential of PMSCs, and reveal ICAM-1 as having a dual role in spheroid formation as well as modulation of immune responses. Our study also highlights the importance of understanding source-specific differences as well as the profound influence of 3D in vitro systems on MSC functions.

关键词： 大鼠   椎间盘   前屈   姿势   生物力学   有限元   X射线   椎间盘角  

摘要： 背景:作者课题组前期构建了一种新型大鼠腰椎力学模型,该模型通过特定装置将大鼠腰椎长期固定于异常前屈姿势,成功诱导L_(6)-S_(1)节段退变。然而,目前尚缺乏对该模型的生物力学相关评估。目的:通过X射线片验证和有限元模型分析,评估大鼠异常前屈姿势下L_(6)-S_(1)节段的生物力学特性。方法:基于课题组前期建立的SD大鼠异常前屈姿势模型,选取3只健康雌性SD大鼠,在未麻醉捆绑和麻醉放松状态下拍摄侧位X射线片,测量L_(6)-S_(1)椎间盘角,分析L_(6)-S_(1)节段在不同姿势下的椎间盘角变化;基于1只健康雌性SD大鼠的Micro-CT扫描数据,利用Mimics、Geomagic Wrap和SolidWorks重建L_(6)-S_(1)节段三维模型,并在ANSYS Workbench中进行网格划分、材料赋值及前屈加载模拟,计算L_(6)-S_(1)椎间盘各组织结构的应力分布。结果与结论:①L_(6)-S_(1)椎间盘角在放松、捆绑姿势下平均值分别为(12.16±0.57)°,(1.26±0.26)°;②在L_(6)-S_(1)椎间盘前屈10°姿势下,椎间盘上终板、下终板、纤维环、髓核的最大等效应力分别为10.398,19.928,6.819,0.104 MPa,其中,上下终板最大von-Mises应力明显高于纤维环和髓核;③提示在L_(6)-S_(1)椎间盘前屈10°造模姿势下,L_(6)-S_(1)椎间盘角减小,致使L_(6)-S_(1)椎间盘形态及受力负荷发生显著变化;构建的有限元模型模拟了大鼠异常前屈姿势下L_(6)-S_(1)椎间盘的生物力学环境,该姿势下的上下终板承受较大等效应力,可能是此模型中理论上最早出现退行性改变的结构。