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排序方式: 共有361条查询结果,搜索用时 15 毫秒
91.
Hao Zhou Yuanyuan Qu E. Shen Chunlei Kong Xuwang Zhang Qiao Ma Jiti Zhou 《Applied microbiology and biotechnology》2013,97(12):5343-5350
meta-Cleavage product (MCP) hydrolases can catalyze relatively low reactive carbon–carbon bond hydrolysis of products, which are derived from the meta-cleavage of catechols. The strict substrate selectivity of MCP hydrolases attracts an interest to understand the determinants of substrate specificity. Compared with conventional site-directed mutagenesis, domain swapping is an effective strategy to explore substrate specificity due to the large-scale reorganization of three-dimensional structure. In the present study, the hybrid MCP hydrolases BphDLidA and MfphALidD were constructed by exchanging the lid domain of two parental enzymes MfphA and BphD. The residues Gly130/Ala196 (MfphA) and Gly136/Ala211 (BphD) were selected as crossover points according to structural disruption score analysis and molecular dynamics simulations. It was shown that the hybrid enzymes exhibited similar substrate selectivity with the parent enzyme providing the lid domain. Docking studies suggested that the lid domain may play a key role in determining substrate specificity by reshaping the active pocket and modulating the orientation of the substrate. 相似文献
92.
Penehyclidine hydrochloride (PHC) can protect against myocardial ischemia/reperfusion (I/R) injury. However, the possible mechanisms of PHC in anoxia/reoxygenation (A/R)‐induced injury in H9c2 cells remain unclear. In the present study, H9c2 cells were pretreated with PI3K/Akt inhibitor LY294002, ATP‐sensitive K+ (KATP) channel blocker 5‐hydroxydecanoate (5‐HD), PHC, or KATP channel opener diazoxide (DZ) before subjecting to A/R injury. Cell viability and cell apoptosis were determined by cell counting kit‐8 assay and annexin V/PI assay, respectively. Myocardial injury was evaluated by measuring creatine kinase (CK) and lactate dehydrogenase (LDH) activities. Intracellular Ca2+ levels, reactive oxygen species (ROS) generation, mitochondrial membrane potential (ΔΨm), and mitochondrial permeability transition pore (mPTP) were measured. The levels of cytoplasmic/mitochondrial cytochrome c (Cyt‐C), Bax, Bcl‐2, cleaved caspase‐3, KATP channel subunits (Kir6.2 and SUR2A), and the members of the Akt/GSK‐3β and Akt/mTOR signaling pathways were determined by western blotting. We found that PHC preconditioning alleviated A/R‐induced cell injury by increasing cell viability, reducing CK and LDH activities, and inhibiting cell apoptosis. In addition, PHC preconditioning ameliorated intracellular Ca2+ overload and ROS production, accompanied by inhibition of both mPTP opening and Cyt‐C release into cytoplasm, and maintenance of ΔΨm. Moreover, PHC preconditioning activated mitochondrial KATP channels, and modulated the Akt/GSK‐3β and Akt/mTOR signaling pathways. Similar effects were observed upon treatment with DZ. Pretreatment with LY294002 or 5‐HD blocked the beneficial effects of PHC. These results suggest that the protective effects of PHC preconditioning on A/R injury may be related to mitochondrial KATP channels, as well as the Akt/GSK‐3β and Akt/mTOR signaling pathways. 相似文献
93.
Zhenfang Liu Fanghui Ye Haiying Zhang Yong Gao Aihua Tan Shijun Zhang Qiang Xiao Bing Zhang Lulu Huang Bingbing Ye Xue Qin Chunlei Wu Zheng Lu Youjie Zhang Ming Liao Xiaobo Yang Zengnan Mo 《PloS one》2013,8(10)
Background
The ferritin is an important participant of iron-storage but its regulation and related factors were not well defined. The present objective was to explore the potential association between serum ferritin levels and sex hormones.Methods
1999 Chinese men in the Fangchenggang Area Male Health and Examination Survey (FAMHES) were recruited in this cross-sectional study. Levels of serum ferritin, total testosterone (free testosterone was calculated from the total one), estradiol and sex hormone-binding protein were detected in venous blood samples. The effects of age, BMI, smoking as well as alcohol consumption were analyzed on ferritin levels, respectively, and then the Pearson’s correlation analysis was used to evaluate the association between ferritin levels and sex hormones adjusting for the above factors.Results
The age, BMI and alcohol consumption significantly affected serum ferritin levels, but there was no significant difference between smokers and nonsmokers. Ferritin levels were significantly and negatively associated with total testosterone (R = −0.205, P< 0.001), sex hormone-binding protein (R = −0.161, P<0.001) and free testosterone (R = −0.097, P<0.001). After age and alcohol consumption were adjusted, the above associations were still significant (R = −0.200, −0.181 and −0.083, respectively, all P<0.001). However, there was only borderline negative association between ferritin levels and estradiol (adjusted R = −0.039, P = 0.083).Conclusion
The large scale of epidemic results showed the significantly negative associations between serum ferritin levels and sex hormones, which may provide more clues to explore the potential regulation and biological mechanism of ferritin. 相似文献94.
The potential of aptamers as ligand binding molecule has opened new avenues in the development of biosensors for cancer oncoproteins. In this paper, a label-free detection strategy using signaling aptamer/protein binding complex for platelet-derived growth factor (PDGF-BB) oncoprotein detection is reported. The detection mechanism is based on the release of fluorophore (TOTO intercalating dye) from the target binding aptamer's stem structure when it captures PDGF. Amino-terminated three-dimensional carbon microarrays fabricated by pyrolyzing patterned photoresist were used as a detection platform. The sensor showed near linear relationship between the relative fluorescence difference and protein concentration even in the sub-nanomolar range with an excellent detection limit of 5pmol. This detection strategy is promising in a wide range of applications in the detection of cancer biomarkers and other proteins. 相似文献
95.
Ji Chunlei Bu Ye Tian Chunyuan Fan Lijun Liu Shoujun Liu Ying Sun Dianjun 《Biological trace element research》2020,193(1):36-43
Biological Trace Element Research - The objectives of this study were to explore reference intervals of ratios of concentrations of urinary iodine to creatinine (UIC/UCr) in pregnant women, to... 相似文献
96.
Chunlei Li Hongmei Xu Jing Xu Xiaoya Chun Dejiang Ni 《Acta Physiologiae Plantarum》2011,33(3):973-978
Seedlings of Camellia sinensis (L.) were grown hydroponically to study the effect of aluminium (Al) on leaf antioxidant defence system and cell ultrastructure.
We found that malondialdehyde (MDA) content decreased at 0–0.32 mM Al, but increased significantly at 0.53 mM Al. Like MDA,
hydrogen peroxide (H2O2) content increased at 0.53 mM Al; however, no differences were observed at 0–0.32 mM Al. Superoxide dismutase (SOD, EC1.15.1.1)
activity remained practically constant at 0–0.32 mM Al, but increased sharply at 0.53 mM Al; catalase (CAT, EC1.11.1.6) and
guaiacol peroxidase (GPX, EC1.11.1.7) activities decreased following an initial increase, reaching their peaks at 0.32 mM
Al. Ascorbate peroxidase (APX, EC 1.11.1.11) activity increased and glutathione (GR, EC 1.6.4.2) level fluctuated with increasing
Al concentrations. Transmission electron microscope analysis of Al-treated leaves showed that although cell ultrastructural
integrity was maintained at 0–0.32 mM, significant membrane damage was observed at 0.53 mM. Our results suggest that at low
Al concentrations, the leaf antioxidant defence system can scavenge reactive oxygen species and sufficiently protect cells
from free radical injury. However, at higher Al concentrations (0.53 mM), the balance between formation and detoxification
of ROS is lost, resulting in the destruction of cell ultrastructure. 相似文献
97.
98.
Wangping Yue Xingtang Fang Chunlei Zhang Yonghong Pang Haixia Xu Chuanwen Gu Ruying Shao Chuzhao Lei Hong Chen 《Molecular biology reports》2011,38(5):2927-2932
The ATP-binding cassette transporter ABCG2 (also known as breast cancer resistance protein, BCRP) belongs to the ATP-binding cassette (ABC) family of transmembrane drug transporters, playing a crucial role in the protection
of various cells and tissues against xenotoxins and/or endotoxins. Recently, several studies have proposed it as the potential
gene underlying the QTL on bovine chromosome 6. Hence, in this study, the PCR-SSCP method was applied to detect two polymorphisms
(A → C and A → G) in the target sequence coding nucleotide-binding domain (NBD) region of ABCG2 and evaluate its associations with milk production traits and mastitis-related traits among Chinese Holsteins. In the analyzed
population, the allelic frequencies for the A and B alleles were 0.5990 and 0.4010, respectively and the genotypic frequencies
were in Hardy–Weinberg disequilibrium (P < 0.01). Moreover, significant statistical relationships between the polymorphisms of ABCG2 gene and following traits, including milk yields, milk protein percentage and somatic cell scores (SCS), were found (P < 0.05). When compared with AA genotype, BB genotype was associated with higher milk yields during 1st and 2nd lactations,
as well as lower milk protein percentage and SCS. Thus, BB genotype is suggested to be a molecular marker for superior milk
performance. 相似文献
99.
Ferreira IM Vidal JE de Mattos Cde C de Mattos LC Qu D Su C Pereira-Chioccola VL 《Experimental parasitology》2011,129(2):190-195
This study investigated the genetic characteristics of Toxoplasma gondii samples collected from 62 patients with toxoplasmosis in Sao Paulo State, Brazil. DNA samples were isolated from blood, cerebrospinal fluid and amniotic fluids of 25 patients with cerebral toxoplasmosis and AIDS, two patients with acute toxoplasmosis, 12 patients with ocular toxoplasmosis, six newborns with congenital toxoplasmosis and 17 pregnant women with acute infection. Diagnosis of toxoplasmosis was based in clinical, radiological and laboratory features. Genotyping was performed using multilocus PCR–RFLP genetic markers including SAG1, SAG2, 5′- and 3′-SAG2, alt.SAG2, SAG3, BTUB, GRA6, C22-8, c29-2, L358, PK1 and Apico. Among the 62 clinical samples, 20 (32%) were successfully genotyped at eight or more genetic loci and were grouped to three distinct genotypes. Eighteen samples belonged to ToxoDB Genotype #65 and the other two samples were identified as ToxoDB Genotypes #6 and #71, respectively (http://toxodb.org/toxo/). Patients presenting Genotypes #6 and #71 had severe and atypical cerebral toxoplasmosis, characterized by diffuse encephalitis without extensive brain lesions. These results indicate that T. gondii Genotype #65 may have a high frequency in causing human toxoplasmosis in Sao Paulo State, Brazil. This unusual finding highlights the need to investigate the possible association of parasite genotypes with human toxoplasmosis. 相似文献
100.
DNA/DNA duplex formation is the basic mechanism that is used in genome tiling arrays and SNP arrays manufactured by Affymetrix. However, detailed knowledge of the physical process is still lacking. In this study, we show a free energy analysis of DNA/DNA duplex formation these arrays based on the positional-dependent nearest-neighbor (PDNN) model, which was developed previously for describing DNA/RNA duplex formation on expression microarrays. Our results showed that the two ends of a probe contribute less to the stability of the duplexes and that there is a microarray surface effect on binding affinities. We also showed that free energy cost of a single mismatch depends on the bases adjacent to the mismatch site and obtained a comprehensive table of the cost of a single mismatch under all possible combination of adjacent bases. The mismatch costs were found to be correlated with those determined in aqueous solution. We further demonstrate that the DNA copy number estimated from the SNP array correlates negatively with the target length; this is presumably caused by inefficient PCR amplification for long fragments. These results provide important insights into the molecular mechanisms of microarray technology and have implications for microarray design and the interpretation of observed data. 相似文献