小鼠肝脏金属硫蛋白Metallothioneins的分离纯化与鉴定

由健康小鼠通过皮下注射一定量的氯化镉,取肝脏匀浆,离心,经SephadexG-50和DEAE-Sephadex A-50柱层析分离,即可获得MT-Ⅰ和MT-Ⅱ两种金属硫蛋白。经鉴定:两个分子各含18个巯基,结合4个Cd原子和3个Zn原子,无金属蛋白质Thionein的分子量约为6kD,半胱氨酸含量约占氨基酸总量的28％,所提取到的MT-Ⅰ和MT-Ⅱ经氨基酸组成,HPLC和PAGE分析皆证明为高度均一的,且与有关文献报道基本相符。其中MT-Ⅱ已获得晶体。     

Conformation and structure of 2-amino-8-(β-d-ribofuranosyl)imidazo [1,2-a]-s-triazin-4-one (5-aza-7-deaza guanosine), a potent antiviral nucleoside

The crystal and molecular structure of one imidazo[1,2-a]-s-triazine nucleoside and its antiviral activity are described. The crystal structure of 2-amino-8-(β-d-ribofuranosyl)imidazo-[1,2-a]-s-triazin-4-one monohydrate (C₁₀H₁₃N₅O₅·H₂O) was solved by X-ray counter data. The compound crystallizes in the monoclinic space group P2₁ with cell dimensions a = 7.353 (1), b = 6.465 (1), c = 13.701 (1) Å, β = 104.64 (1)°. The structure was solved by direct methods and refined by full matrix least-squares technique to a final value of the conventional R-factor of 0.049 using 1998 observed intensities. The orientation of the base relative to the sugar ring defined in terms of rotation about the C(1′)-N(8) glycosyl bond is anti (47.8°). The ribose moiety exhibits C(2′)-endo, ²E conformation. The conformation around C(4′)-C(5′) is gauche^?. Molecular packing is dominated by hydrogen bonds. Base stacking occurs long the b axis. 5-Aza-7-deazaguanosine has shown a marked antiviral activity in vitro against herpes simplex virus despite the fact that N(3) is effective as the hydrogen acceptor only.     

Glucose biosensor based on electrodeposited platinum nanoparticles and three-dimensional porous chitosan membranes

The chitosan with three-dimensional porous structure greatly increased the effective electrode surface for loading of platinum nanoparticles and promoted efficient electron transfer. The resulting biosensor had a response time (within 5 s) and a linear response from 6 μM to 4.2 mM glucose with a detection limit of 2 μM (S/N = 3). Moreover, the methodology can be applied for the immobilization of other enzymes.     

Queuosine Biosynthesis Is Required for Sinorhizobium meliloti-Induced Cytoskeletal Modifications on HeLa Cells and Symbiosis with Medicago truncatula

Rhizobia are symbiotic soil bacteria able to intracellularly colonize legume nodule cells and form nitrogen-fixing symbiosomes therein. How the plant cell cytoskeleton reorganizes in response to rhizobium colonization has remained poorly understood especially because of the lack of an in vitro infection assay. Here, we report on the use of the heterologous HeLa cell model to experimentally tackle this question. We observed that the model rhizobium Sinorhizobium meliloti, and other rhizobia as well, were able to trigger a major reorganization of actin cytoskeleton of cultured HeLa cells in vitro. Cell deformation was associated with an inhibition of the three major small RhoGTPases Cdc42, RhoA and Rac1. Bacterial entry, cytoskeleton rearrangements and modulation of RhoGTPase activity required an intact S. meliloti biosynthetic pathway for queuosine, a hypermodifed nucleoside regulating protein translation through tRNA, and possibly mRNA, modification. We showed that an intact bacterial queuosine biosynthetic pathway was also required for effective nitrogen-fixing symbiosis of S. meliloti with its host plant Medicago truncatula, thus indicating that one or several key symbiotic functions of S. meliloti are under queuosine control. We discuss whether the symbiotic defect of que mutants may originate, at least in part, from an altered capacity to modify plant cell actin cytoskeleton.     

Arabidopsis ADC1 functions as an N~δ-acetylornithine decarboxylase

Polyamines are small aliphatic amines found in almost all organisms, ranging from bacteria to plants and animals. In most plants, putrescine, the metabolic precursor for longer polyamines, such as spermidine and spermine, is produced from arginine, with either agmatine or ornithine as intermediates. Here we show that Arabidopsis thaliana(Arabidopsis) arginine decarboxylase 1(ADC1), one of the two known arginine decarboxylases in Arabidopsis, not only synthesizes agmatine from arginine, but also converts N~δ-acetylornithine to N-acetylputrescine. Phylogenetic analyses indicate that duplication and neofunctionalization of ADC1 and NATA1, the enzymes that synthesize N~δ-acetylornithine in Arabidopsis, co-occur in a small number of related species in the Brassicaceae. Unlike ADC2, which is localized in the chloroplasts, ADC1 is in the endoplasmic reticulum together with NATA1, an indication that these two enzymes have access to the same substrate pool. Together, these results are consistent with a model whereby NATA1 and ADC1 together provide a pathway for the synthesis of N-acetylputrescine in Arabidopsis.     

Deficiency of Macf1 in osterix expressing cells decreases bone formation by Bmp2/Smad/Runx2 pathway

Microtubule actin cross‐linking factor 1 (Macf1) is a spectraplakin family member known to regulate cytoskeletal dynamics, cell migration, neuronal growth and cell signal transduction. We previously demonstrated that knockdown of Macf1 inhibited the differentiation of MC3T3‐E1 cell line. However, whether Macf1 could regulate bone formation in vivo is unclear. To study the function and mechanism of Macf1 in bone formation and osteogenic differentiation, we established osteoblast‐specific Osterix (Osx) promoter‐driven Macf1 conditional knockout mice (Macf1^f/fOsx‐Cre). The Macf1^f/fOsx‐Cre mice displayed delayed ossification and decreased bone mass. Morphological and mechanical studies showed deteriorated trabecular microarchitecture and impaired biomechanical strength of femur in Macf1^f/fOsx‐Cre mice. In addition, the differentiation of primary osteoblasts isolated from calvaria was inhibited in Macf1^f/fOsx‐Cre mice. Deficiency of Macf1 in primary osteoblasts inhibited the expression of osteogenic marker genes (Col1, Runx2 and Alp) and the number of mineralized nodules. Furthermore, deficiency of Macf1 attenuated Bmp2/Smad/Runx2 signalling in primary osteoblasts of Macf1^f/fOsx‐Cre mice. Together, these results indicated that Macf1 plays a significant role in bone formation and osteoblast differentiation by regulating Bmp2/Smad/Runx2 pathway, suggesting that Macf1 might be a therapeutic target for bone disease.     

Charge Transfer Modulated Activity of Carbon‐Based Electrocatalysts

Electrocatalysis is the most important electrode reactions for many energy storage and conversion devices, which are considered a key part of the resolution of the energy crisis. Toward this end, design of efficient electrocatalysts is of critical significance. While extensive research has been extended to develop excellent electrocatalysts, the fundamental understanding of the relationship between the electronic and structural properties of electrocatalysts and the catalytic activity must remain a priority. In this review, the activity modulation of electrocatalysts by charge transfer effects, including intramolecular and intermolecular charge transfer, is systematically introduced. With suitable charge transfer modification, such as heteroatom doping, defect engineering, molecule functionalization, and heterojunctions, the electrocatalytic activity of carbon‐based electrocatalysts can be significantly boosted. The manipulation of the electronic structure of carbon‐based materials by charge transfer may serve as a fundamental mechanism for performance enhancement. After establishing an understanding of the relationship between catalytic activity and charge transfer, the opportunities and challenges for the design of electrocatalyst with charge transfer effects are discussed.     

NF-κB在幽门螺杆菌感染介导的胃癌发生发展中的作用

目的:探讨核因子-κB(nuclear factor-κB,NF-κB)在幽门螺杆菌感染介导的胃癌发生发展中的作用。方法:选择2016年3月至2019年3月在本院诊治的胃部疾病患者110例,采用qPCR检测NF-κB相对表达情况,采用免疫印记法检测幽门螺杆菌(Helicobacter pylori,Hp)感染情况并进行相关性分析。结果:在110例患者中,病理诊断为胃癌9例(胃癌组)和良性胃部疾病101例(良性组,其中浅表性胃炎52例、萎缩性胃炎26例、不典型增生23例)。胃癌组的幽门螺杆菌感染率为88.9%,显著高于良性组的10.9%(P0.05)。胃癌组的NF-κB表达阳性率为77.8%,显著高于良性组的14.9%(P0.05)。在110例患者中,直线相关性分析显示幽门螺杆菌感染、NF-κB表达阳性与胃癌有显著正相关性(P0.05)。受试者工作特征曲线(receiver operating characteristic curve,ROC)显示幽门螺杆菌感染、NF-κB表达阳性鉴别诊断胃癌的曲线下面积分别为0.669和0.713。结论:NF-κB在胃癌中呈现高表达状况,也多伴随有幽门螺杆菌感染,两者存在显著相关性,共同介导胃癌的发生发展。