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21.
热休克蛋白gp96是热休克蛋白90家族成员,能够引起非特异性和特异性免疫反应。得到大量高纯度的蛋白质是研究开发gp96的关键。然而重组的gp96容易在E.coli中降解,并在一定条件下形成多聚体。实验先将人gp96基因克隆到pET-30a载体上并在E.coli Blstar中表达,再经过亲和层析、阴离子交换、分子筛分别纯化gp96。最终去掉了大部分的降解片段和多聚体,得到一定量的可溶性gp96,为进一步研究其结构和功能打下一定的基础。  相似文献   
22.
Ovarian clear cell adenocarcinoma (CCC) is the second most common subtype of ovarian cancer after high-grade serous adenocarcinomas. CCC tends to develop resistance to the standard platinum-based chemotherapy, and has a poor prognosis when diagnosed in advanced stages. The ANXA4 gene, along with its product, a Ca++-binding annexin A4 (ANXA4) protein, has been identified as the CCC signature gene. We reported two subtypes of ANXA4 with different isoelectric points (IEPs) that are upregulated in CCC cell lines. Although several in vitro investigations have shown ANXA4 to be involved in cancer cell proliferation, chemoresistance, and migration, these studies were generally based on its overexpression in cells other than CCC. To elucidate the function of the ANXA4 in CCC cells, we established CCC cell lines whose ANXA4 expressions are stably knocked down. Two parental cells were used: OVTOKO contains almost exclusively an acidic subtype of ANXA4, and OVISE contains predominantly a basic subtype but also a detectable acidic subtype. ANXA4 knockdown (KO) resulted in significant growth retardation and greater sensitivity to carboplatin in OVTOKO cells. ANXA4-KO caused significant loss of migration and invasion capability in OVISE cells, but this effect was not seen in OVTOKO cells. We failed to find the cause of the different IEPs of ANXA4, but confirmed that the two subtypes are found in clinical CCC samples in ratios that vary by patient. Further investigation to clarify the mechanism that produces the subtypes is needed to clarify the function of ANXA4 in CCC, and might allow stratification and improved treatment strategies for patients with CCC.  相似文献   
23.
The DNA replicase activity of the complex between bovine thymus DNA polymerase alpha and RNA primase was markedly decreased after the purification by ssDNA-cellulose column chromatography. In an attempt to restore the activity by supplementing some fractions eliminated from the purified enzyme, we found that a fraction eluted from the column by increasing salt concentration and 30% ammonium sulfate precipitates of the phosphocellulose-step enzyme possessed a high ability to restore the replicase activity. Thus, the factors were purified to near homogeneity from the two sources and the properties were examined. Both factors were heat-labile and trypsin-sensitive, possessed a native molecular mass of approximately 150-200 kDa as judged by Sephacryl S-200 column chromatography, and were composed of two polypeptides of 146 kDa and 47 kDa on SDS/polyacrylamide gel electrophoresis, indicating that they were an identical protein. The factor, which did not show any DNA polymerase or primase activities by itself, stimulated approximately 20-fold the replicase activity of purified DNA-polymerase-alpha-primase at a very low concentration (10 ng/50 microliter). The factor did not affect the deoxyribonucleotide polymerizing activity of the enzyme complex at all, but specifically stimulated the primase activity only. Thus, we designated the factor as primase-stimulating factor. Although varying the template concentration did not significantly affect the mode of stimulation, increasing the concentration of substrate for primer synthesis (ATP) markedly decreased the extent of stimulation. Thus, the stimulating factor seems to decrease the substrate concentration required for the primase reaction as well as increasing threefold the maximum activity attained by varying the substrate concentration. So far, no ATPase activity has been detected in the factor.  相似文献   
24.
Two compounds were isolated from alfalfa. Their structures were determined as benzoyl meso-tartaric acid (I) and benzoyl (S), (–)-malic acid (II) respectively. They were found in nature for the first time.  相似文献   
25.
毛乌素沙地南缘沙丘生物结皮对凝结水形成和蒸发的影响   总被引:5,自引:0,他引:5  
在水分极度匮乏的荒漠生态系统,凝结水是除降雨之外最重要的水分来源之一,它对荒漠生态系统结构、功能和过程的维持产生重要的影响。为探明半干旱沙区生物结皮表面的凝结水形成和蒸发特征,采用自制的微型蒸渗计(直径7 cm、高5 cm的PVC管)实验观测了不同类型地表(裸沙、浅灰色藻类结皮、黑褐色藻类结皮和苔藓结皮)对凝结水形成和蒸发的影响。结果表明:(1)观测期间共有20次凝结水形成记录,除降雨天气外,几乎每天都能观测到水分凝结现象;(2)不同类型地表凝结水总量依次为(1.998±0.075),(2.326±0.083),(2.790±0.058)和(3.416±0.068) mm,生物结皮表面的凝结水总量显著大于裸沙(P < 0.05);随生物结皮的发育,不同类型生物结皮表面的凝结水总量呈增加的趋势,凝结水总量之间差异显著(P < 0.05);观测期间不同类型地表日平均凝结水量依次为(0.100±0.003),(0.116±0.004),(0.140±0.002)和(0.171± 0.003) mm,不同类型地表日平均凝结水量之间差异极显著(P < 0.01);(3)凝结水形成过程的观测结果显示,凝结水19:00开始形成,23:00-凌晨1:00形成不明显,1:00-7:00继续形成,除浅灰色藻类结皮外,太阳升出后在黑褐色藻类结皮和苔藓结皮表面继续形成少量的凝结水;凝结水7:30开始蒸发,10:30到11:00之间结束蒸发,凝结水在裸沙和浅灰色藻类结皮中的保持时间显著大于黑褐色藻类结皮和苔藓结皮中的保持时间(P < 0.05);(4)凝结水的形成受大气温度、地表温度、空气相对湿度和大气地表温度差等气象因素的影响,但其形成过程不与某一个气象因素呈简单的线性关系。  相似文献   
26.
Temperament differs among individuals both within and between species. Evidence suggests that differences in temperament of group members may parallel differences in social behavior among groups or between species. Here, we compared temperament between three closely related species of monkey—rhesus (Macaca mulatta), long‐tailed (M. fascicularis), and pigtailed (M. nemestrina) macaques—using cage‐front behavioral observations of individually housed monkeys at a National Primate Research Center. Frequencies of 12 behaviors in 899 subjects were analyzed using a principal components analysis to identify temperament components. The analysis identified four components, which we interpreted as Sociability toward humans, Cautiousness, Aggressiveness, and Fearfulness. Species and sexes differed in their average scores on these components, even after controlling for differences in age and early‐life experiences. Our results suggest that rhesus macaques are especially aggressive and unsociable toward humans, long‐tailed macaques are more cautious and fearful, and pigtailed macaques are more sociable toward humans and less aggressive than the other species. Pigtailed males were notably more sociable than any other group. The differences observed are consistent with reported variation in these species’ social behaviors, as rhesus macaques generally engage in more social aggression and pigtailed macaques engage in more male–male affiliative behaviors. Differences in predation risks are among the socioecological factors that might make these species‐typical behaviors adaptive. Our results suggest that adaptive species‐level social differences may be encoded in individual‐level temperaments, which are manifested even outside of a social context. Am. J. Primatol. 75:303‐313, 2013. © 2012 Wiley Periodicals, Inc.  相似文献   
27.
28.
The recruitment of tissue‐resident stem cells is important for wound regeneration. Periodontal ligament cells (PDL cells) are heterogeneous cell populations with stemness features that migrate into wound sites to regenerate periodontal fibres and neighbouring hard tissues. Cell migration is regulated by the local microenvironment, coordinated by growth factors and the extracellular matrix (ECM). Integrin‐mediated cell adhesion to the ECM provides essential signals for migration. We hypothesized that PDL cell migration could be enhanced by selective expression of integrins. The migration of primary cultured PDL cells was induced by platelet‐derived growth factor‐BB (PDGF‐BB). The effects of blocking specific integrins on migration and ECM adhesion were investigated based on the integrin expression profiles observed during migration. Up‐regulation of integrins α3, α5, and fibronectin was identified at distinct localizations in migrating PDL cells. Treatment with anti‐integrin α5 antibodies inhibited PDL cell migration. Treatment with anti‐integrin α3, α3‐blocking peptide, and α3 siRNA significantly enhanced cell migration, comparable to treatment with PDGF‐BB. Furthermore, integrin α3 inhibition preferentially enhanced adhesion to fibronectin via integrin α5. These findings indicate that PDL cell migration is reciprocally regulated by integrin α3‐mediated inhibition and α5‐mediated promotion. Thus, targeting integrin expression is a possible therapeutic strategy for periodontal regeneration.  相似文献   
29.
干扰素研究及应用进展   总被引:3,自引:0,他引:3  
1957年,英国科学家Isaacs和Lindenmann利用鸡胚绒毛尿囊研究流感干扰现象时,发现一种能够干扰病毒繁殖的物质,称之为干扰素(IFN),由于干扰素对许多疾病有很好的治疗作用,一直是医学领域研究的重要物质之一。现在干扰素已成功地用于肝炎、肿瘤治疗等方面。为了充分发挥干扰素的作用,人们稍用基因工程的方法来对干扰素的产量及功效进行改进,已达到更好的应用,因此基因工程干扰素越来越多地成了研究的重点。  相似文献   
30.
The gene, pixJ1 (formerly pisJ1), is predicted to encode a phytochrome-like photoreceptor that is essential for positive phototaxis in the unicellular cyanobacterium Synechocystis sp. PCC 6803 [Yoshihara et al. (2000) Plant Cell Physiol. 41: 1299]. The PixJ1 protein was overexpressed as a fusion with a poly-histidine tag (His-PixJ1) and isolated from Synechocystis cells. A zinc-fluorescence assay suggested that a linear tetrapyrrole was covalently attached to the His-PixJ1 protein as a chromophore. His-PixJ1 showed novel photoreversible conversion between a blue light-absorbing form (Pb, lambdaAmax=425-435 nm) and a green light-absorbing form (Pg, lambdaAmax=535 nm). Dark incubation led Pg to revert to Pb, indicative of stability of the Pb form in darkness. Red or far-red light irradiation, which is effective for photochemical conversion of the known phytochromes, produced no change in the spectra of Pb and Pg forms. Site-directed mutagenesis revealed that a Cys-His motif in the second GAF domain of PixJ1 is responsible for binding of the chromophore. Possible chromophore species are discussed with regard to the novel photoconversion spectrum.  相似文献   
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