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941.
Formation and movement of Fe(III) in horse spleen, H- and L-recombinant ferritins. A fluorescence study. 下载免费PDF全文
S. Cavallo G. Mei S. Stefanini N. Rosato A. Finazzi-Agr E. Chiancone 《Protein science : a publication of the Protein Society》1998,7(2):427-432
Iron oxidation and incorporation into apoferritins of different subunit composition, namely the recombinant H and L homopolymers and the natural horse spleen heteropolymer (10-15% H), have been followed by steady-state and time-resolved fluorescence. After aerobic addition of 100 Fe(II) atoms/polymer, markedly different kinetic profiles are observed. In the rL-homopolymer a slow monotonic fluorescence quenching is observed which reflects binding, slow oxidation at the threefold apoferritin channels, and diffusion into the protein cavity. In the rH-homopolymer a fast fluorescence quenching is followed by a partial, slow recovery. The two processes have been attributed to Fe(II) binding and oxidation at the ferroxidase centers and to Fe(III) released into the cavity, respectively. The fluorescence kinetics of horse spleen apoferritin is dominated by the H chain contribution and resembles that of the H homopolymer. It brings out clearly that the rate of the overall process is limited by the rate at which Fe(III) leaves the ferroxidase centers of the H chains where binding of incoming Fe(II) and its oxidation take place. The data obtained upon stepwise addition of iron and the results of optical absorption measurements confirm this picture. The correspondence between steady-state and time-resolved data is remarkably good; this is manifest when the latter are used to calculate the change in fluorescence intensity as apparent in the steady-state measurements. 相似文献
942.
Amino acid starvation‐induced LDLR trafficking accelerates lipoprotein endocytosis and LDL clearance
Ye Chen Xiao Wu Jing Zhang Guopin Pan Xiaoyun Wang Xiaosun Guo Jianli Wang Xiaopei Cui Haiqing Gao Mei Cheng Jingwen Yang Cheng Zhang Fan Jiang 《EMBO reports》2022,23(3)
Mammalian cells utilize Akt‐dependent signaling to deploy intracellular Glut4 toward cell surface to facilitate glucose uptake. Low‐density lipoprotein receptor (LDLR) is the cargo receptor mediating endocytosis of apolipoprotein B‐containing lipoproteins. However, signaling‐controlled regulation of intracellular LDLR trafficking remains elusive. Here, we describe a unique amino acid stress response, which directs the deployment of intracellular LDLRs, causing enhanced LDL endocytosis, likely via Ca2+ and calcium/calmodulin‐dependent protein kinase II‐mediated signalings. This response is independent of induction of autophagy. Amino acid stress‐induced increase in LDL uptake in vitro is comparable to that by pravastatin. In vivo, acute AAS challenge for up to 72 h enhanced the rate of hepatic LDL uptake without changing the total expression level of LDLR. Reducing dietary amino acids by 50% for 2 to 4 weeks ameliorated high fat diet‐induced hypercholesterolemia in heterozygous LDLR‐deficient mice, with reductions in both LDL and VLDL fractions. We suggest that identification of signaling‐controlled regulation of intracellular LDLR trafficking has advanced our understanding of the LDLR biology, and may benefit future development of additional therapeutic strategies for treating hypercholesterolemia. 相似文献
943.
Liu Yang Lingyang Xu Yang Zhou Mei Liu Lei Wang James W. Kijas Hongping Zhang Li Li George E. Liu 《Genomics》2018,110(3):143-148
Copy number variation (CNV) represents a major source of genomic variation. We investigated the diversity of CNV distribution using SNP array data collected from a comprehensive collection of geographically dispersed sheep breeds. We identified 24,558 putative CNVs, which can be merged into 619 CNV regions, spanning 197 Mb of total length and corresponding to ~ 6.9% of the sheep genome. Our results reveal a population differentiation in CNV between different geographical areas, including Africa, America, Asia, Southwestern Asia, Central Europe, Northern Europe and Southwestern Europe. We observed clear distinctions in CNV prevalence between diverse groups, possibly reflecting the population history of different sheep breeds. We sought to determine the gene content of CNV, and found several important CNV-overlapping genes (BTG3, PTGS1 and PSPH) which were involved in fetal muscle development, prostaglandin (PG) synthesis, and bone color. Our study generates a comprehensive CNV map, which may contribute to genome annotation in sheep. 相似文献
944.
磷对土壤中砷吸附的影响 总被引:32,自引:1,他引:32
在黄壤、红壤和褐土中进行As的等温吸附实验表明,在不添加P的情况下,3种土壤对As的吸附能力随土壤pH的升高而降低,随土壤粘粒含量的降低而减弱,3种土壤吸附能力为黄壤>红壤>褐土,As在土壤中的吸附受P存在的影响,60mg·kg-1的P可以降低黄壤和红壤对As最大吸附量.吸附质中P:As的比例不同,P对土壤吸附As的影响差异很大:吸附质中P:As=1:2时,土壤对As的吸附能力均强于P:As=1:1和P:As=2:1,后两者差异不显著,表明土壤中的吸附点位对As和P的亲和性具有一定的差异,Languir方程能很好地拟合所测得的土壤平衡溶液中As浓度。 相似文献
945.
This study shows that both length and distribution of lipopolysaccharide (LPS) are important for Shigella flexneri invasion and virulence. Mutants were generated in the chromosomal LPS synthesis genes rfa , rfb , and rol , and in a plasmid-encoded O-antigen chain-length regulator, cld pHS-2 . LPS analysis showed that mutations in rfb genes and in a candidate rfaL gene either eliminated the entire O-antigen side chains or produced chains of greatly reduced length. Mutation in a previously unidentified gene, rfaX , affected the LPS core region and resulted in reduced amounts of O-antigen. Mutants defective in cld pHS-2 or rol had different distributions of O-antigen chain lengths. The results of tissue-culture cell invasion and plaque assays, the Serény test, and serum-sensitivity assay suggested roles for the different LPS synthesis genes in bacterial survival and virulence; rfaL, rfaX and rfb loci are required for serum resistance and intercellular spread, but not for invasion; cld pHS-2 is required for resistance to serum killing and for full inflammation in the Serény test, but not for invasion or intercellular spread, while rol is required for normal invasiveness and plaque formation, but not for serum resistance. Thus, O-antigen synthesis and chain-length regulation genes encoded on both the chromosome and the small plasmid pHS-2 play important roles in S. flexneri invasion and virulence. 相似文献
946.
Jimei Yu Xin Li Jiezhao Zhou Xiangyang Xie Meiling Chen Xinhua He Yang Yang Youzhi Zhang Aiping Zheng Xingguo Mei Ying Li 《Chirality》2017,29(5):193-201
Ammuxetine (AMT), a novel chiral antidepressant candidate compound, exhibits better antidepression effects than duloxetine in different animal models. In this article, a chiral derivatization method, combined with online solid phase extraction (online SPE) and liquid chromatography–tandem mass spectrometry (LC–MS/MS), was developed for the chiral separation of AMT enantiomers after administration of racemic AMT to dogs. The derivatization reaction employed 2,3,4,6‐tetra‐O‐acetyl‐b‐glucopyr‐anosyl isothiocyanate (GITC) as a precolumn chiral derivatization reagent. A SPE column Retain PEP Javelin (10 × 2.1 mm) was used to remove proteins and other impurities in plasma samples. The enantiomeric derivatives were separated on a ZORBAX SB‐C18 column (50 × 2.1 mm × 3.5 μm) with an isocratic elution procedure. The selected multiple reaction monitoring mode of the positive ion was performed and the parent to the product transitions m/z 681.0/543.1 and m/z 687.4/543.1 were used to measure the derivatives of AMT and duloxetine (internal standard) with electrospray ionization. The method was validated in terms of specificity, linearity, sensitivity, precision, accuracy, matrix effect, and stability. The method was applied to a pharmacokinetics study of AMT racemate in dogs. The results suggested that the pharmacokinetic of AMT enantiomers might be stereoselective in dogs. 相似文献
947.
人肝刺激因子对大鼠实验性慢性肝损伤的保护作用 总被引:3,自引:0,他引:3
从健康孕妇水囊引产4─6个月龄的胎儿取肝,采用LaBrecque方法提取人肝刺激因子(hHSS)。经3H-胸腺嘧啶核苷参入肝DNA法测定其生物活性。表明此hHSS可刺激肝细胞DNA合成。采用皮下注射CCl4和饮用10%乙醇来制备慢性肝损伤动物模型,观察了hHSS的保护肝脏作用。结果表明:hHSS可使CCl4-乙醇所致慢性肝损伤大鼠的死亡率、血清谷丙转氨酶水平、肝组织中羟脯氨酸含量的升高以及肝组织中丙二醛的含量降低。肝组织切片表明:hHSS能减轻肝组织的损伤程度,促进肝细胞再生,并能明显防止肝纤维化的形成和发展。可见,hHSS对CCl4-乙醇所致的慢性肝损伤大鼠有明显的保护作用,其机制可能与促进肝细胞再生及抑制肝细胞膜的脂质过氧化有关。 相似文献
948.
949.
Comparison between the adhesion to solid substrata of Streptococcus mitis and that of polystyrene particles. 下载免费PDF全文
The adhesion of Streptococcus mitis to solid substrata from phosphate suspensions with various ionic strengths was studied and compared with the adhesion of polystyrene particles. At all ionic strengths, the interfacial free energy of adhesion governed the relative number of bacteria or polystyrene particles adhering at equilibrium, except that in a low-ionic-strength buffer, adhesion occurred less frequently because of increased electrostatic repulsion. Large differences between bacterial and polystyrene particle adhesion were observed, as indicated by the ratio of bacteria to polystyrene particles adhering, which decreased from 30 to 4 with a change from low to high ionic strength. 相似文献
950.
SHP2, a protein tyrosine phosphatase with two SH2 domains, has been implicated in regulating acetylcholine receptor (AChR) gene expression and cluster formation in cultured muscle cells. To understand the role of SHP2 in neuromuscular junction (NMJ) formation in vivo, we generated mus cle-specific deficient mice by using a loxP/Cre strategy since Shp2 null mutation causes embryonic lethality. Shp2(floxed/floxed) mice were crossed with mice expressing the Cre gene under the control of the human skeletal alpha-actin (HSA) promoter. Expression of SHP2 was reduced or diminished specifically in skeletal muscles of the conditional knockout (CKO) mice. The mutant mice were viable and fertile, without apparent muscle defects. The mRNA of the AChR alpha subunit and AChR clusters in CKO mice were localized in a narrow central region surrounding the phrenic nerve primary branches, without apparent change in intensity. AChR clusters colocalized with markers of synaptic vesicles and Schwann cells, suggesting proper differentiation of presynaptic terminals and Schwann cells. In comparison with age-matched littermates, no apparent difference was observed in the size and length of AChR clusters in CKO mice. Both the frequency and amplitude of mEPPs in CKO mice were similar to those in controls, suggesting normal neurotransmission when SHP2 was deficient. These results suggest that Shp2 is not required for NMJ formation and/or maintenance. 相似文献