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91.
A novel protein from Gluconobacter oxydans DSM2003 which shows 60–70% similarity with members of aldo–keto reductase (AKR) superfamily was overexpressed in Escherichia coli BL21 (DE3) and purified by one step affinity chromatography with a Ni-NTA agarose column. The recombinant protein (named GOX0644) consists of 279 amino acids with an apparent molecular mass of 32 kDa in the soluble fraction, and the gene sequence encoding the protein GOX0644 is 100% identical to the ORF of gox0644 in G. oxydans 621H (DSM2343). For a detailed analysis of its enzymatic activity, the substrate specificity of the recombinant protein GOX0644 was determined. With NADPH as a cofactor, GOX0644 exhibited better activity to aromatic aldehydes, especially o-chlorobenzaldehyde, compared to aliphatic aldehydes. It showed almost no activity toward glyceraldehyde, xylose, glucose, and ketones. The protein was unable to oxidize primary- or secondary alcohols. Based on these results, GOX0644 was defined as a novel NADPH-dependent aldehyde reductase. Kinetic parameters of the protein and the dependence of its activity on temperature and pH were also determined.  相似文献   
92.
神经节苷脂对细胞膜损伤的保护作用   总被引:6,自引:0,他引:6  
观察了神经节苷脂对去垢剂Triton—X—100损伤大鼠红细胞膜的影响。适量的红细胞与16μg/ml至5×104μg/ml范围内不同浓度的神经节苷脂于37℃孵育1小时后,加入TritonX-100在室温下作用3分钟。离心,取上清液在540nm测溶液透光率,取沉淀部分的红细胞在扫描电镜下观察红细胞及其膜的形态变化。实验结果显示,在神经节苷脂浓度为104μ/ml时,对红细胞膜的保护作用最好,上清液透光率为正常值的85.4%;细胞形态虽有改变,但仍的部分接近正常的细胞存在。而损伤对照组上清透光度仅为正常值的13.4%,红细胞胞体缩小,成为棘形红细胞。结果表明,神经节苷脂对红细胞膜化学损伤有良好的保护作用。  相似文献   
93.
新生大鼠脑低氧缺血早期对纹状体胆碱能系统的影响   总被引:1,自引:0,他引:1  
采用7日龄大鼠右侧颈总动脉结扎合并高温、低氧环境制作新生动物脑低氧缺血模型,观察了脑低氧缺血对新生动物纹状体胆碱能系统的影响。乙酰胆碱(ACh)放射免疫测定结果表明,低氧缺血损伤后24h,两侧纹状体ACh含量均比正常对照组明显下降。乙酰胆碱酯酶(AChE)组织化学图象定量提示,脑低氧缺血后24h,纹状体内拟胆碱能神经元数量未见减少,而胞体内AChE染色强度略有下降。胆碱能递质和该标志酶在新生鼠脑低氧缺血早期的一致改变,证明发育中纹状体胆碱能系统对低氧缺血敏感。鉴于动物不结扎动脉仅作低氧处理者双侧纹状体ACh含量出现与低氧缺血组相同的改变,故提示缺氧可能是造成胆碱能系统早期损伤的直接原因。  相似文献   
94.
An undescribed xanthone dimer, 1,3,5,8-tetrahydroxy-7-(1′,5′,8′-trihydroxy-3′-methoxy-2′-xanthonyl)xanthone ( 1 ) was separated together with eleven known compounds ( 2 – 12 ) from the dried whole herb of Swertia pseudochinensis. It was the first time that the compounds 8 – 12 were isolated from the Swertia genus. The structure of compound 1 was illuminated based on chemical evidence and spectral data analysis (UV, 1D and 2D-NMR, HR-ESI-MS). Moreover, the inhibitory effects of all compounds on NO production in LPS-induced RAW 264.7 cells were tested, compounds 8 , 9 , 10 , 11 and 12 showing significant inhibition. The IC50 value of compound 12 was 3.05±1.10 μM. Using target screening and molecular docking, we hypothesized that compound 12 may bind neutrophil elastase to exert its anti-inflammatory effects.  相似文献   
95.
The Escherichia coli heat-labile enterotoxin B subunit (HLT-B) is one of the most powerful mucosal immunogens and known mucosal adjuvants. However, the induction of high levels of HLT-B expression in E. coli has proven a difficult proposition. Therefore, in this study, the HLT-B gene was cloned from pathogenic E. coli and expressed as a fusion protein with GST (glutathione S-transferase) in E. coli BL21 (DE3), in an attempt to harvest a large quantity of soluble HLT-B. The culture conditions, including the culture media used, temperature, pH and the presence of lactose as an inducer, were all optimized in order to obtain an increase in the expression of soluble GST-rHLT-B. The biological activity of the purified rHLT-B was assayed in a series of GM1-ELISA experiments. The findings of these trials indicated that the yield of soluble recombinant GST-rHLT-B could be increased by up to 3-fold, as compared with that seen prior to the optimization, and that lactose was a more efficient alternative inducer than IPTG. The production of rHLT-B, at 92% purity, reached an optimal level of 96 mg/l in a 3.7 L fermentor. The specific GM1 binding ability of the purified rHLT-B was determined to be almost identical to that of standard CTB.  相似文献   
96.
Exendin-4 is a 39 amino acid peptide isolated from the Gila monster salivary gland. It is 53% homologous to GLP-1 and exhibits similar glucoregulatory activities. In this study, exendin-4 dimer (D-Ex4) was constructed, cloned into plasmid pET32a(+) and expressed in E. coli BL21(DE3). The fusion protein with His-tag at the N-terminus was purified with a Ni-NTA-agarose column. After proteolytic cleavage, D-Ex4 peptide with high purity was obtained by HPLC. The results obtained by chemical cross-linking showed that D-Ex4 maintained affinity to GLP-1 receptor.  相似文献   
97.
The modeled structure of penicillin acylase from Alcaligenes faecali (AFPGA) was constructed by comparative modeling with the Modeller program. Candidate positions that could be replaced with cysteine were estimated by scanning the modeled structure of AFPGA with the program MODIP (modeling disulfide bond in protein). The mutant Q3C/P751C had a higher optimum temperature by three degrees than that of the wild type AFPGA. The half life of the double mutant Q3C/P751C at 55 degrees C was increased by 50%. To our knowledge, this was the first structure-based genetic modification of AFPGA.  相似文献   
98.
由于存在基因工程微生物(GEMs)不受控制地在环境中释放的风险, 利用GEMs的生物降解能力治理环境污染的方法受到了限制。在大肠杆菌JM109中构建了一个受环境污染物调控的细菌遏制系统, 该系统是由杀伤元件和调控元件组成的双质粒体系, 使细菌的存活受环境中水杨酸盐浓度的调控。当培养基含水杨酸盐时, 阻遏蛋白LacI合成, 阻止自杀基因gef表达, 细菌快速繁殖; 当水杨酸盐不存在时, 自杀基因gef的表达导致细胞杀伤, 菌体大量死亡。该遏制系统可作为模型用于具有生物修复功能的基因工程菌的构建。  相似文献   
99.
假型病毒是包被其它囊膜病毒糖蛋白的病毒颗粒.由于假型病毒具有宿主嗜性广、生物安全性高和稳定性强的优点,所以成为基因治疗中向靶细胞呈递治疗基因的有效工具,引起了广泛关注.假型病毒载体将会给基因治疗研究带来新的机遇.因此,将就假型病毒载体的最新研究进展作以综述.  相似文献   
100.
Exendin-4 is a 39 amino acid peptide isolated from salivary secretions of Gila monster (Heloderma suspectum). It shows 53% sequence similarity to glucagon-like peptide-1 (GLP-1), which is evaluated for the regulation of plasma glucose in type 2 diabetes. Exendin-4 is a potent and long-acting agonist of GLP-1 receptor. In the present study, the exendin-4 gene obtained by PCR with an enterokinase site at N-terminus and a termination codon at C-terminus was expressed in Escherichia coli strain BL21 (DE3) harboring pET32a(+). The fusion protein was purified by chromatography on Ni-NTA-agarose column. Recombinant exendin-4 was obtained by enterokinase cleavage of the fusion protein and subsequent purification. The yield of recombinant exendin-4 was 3.15mg/10g bacteria. The obtained recombinant exendin-4 shows glucose-lowering action in vivo.  相似文献   
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