活菌制剂活菌数急剧衰降的原因与减缓衰降的方法

市售活菌制剂口服液活菌数急剧衰降的原因是营养缺乏,特别是缺乏部分氨基酸及某些维生素。增加动物性蛋白胨及强化酵母膏,添加适量维生素可使活菌数一年后保持在１０^６／ｍｌ以上。     

IL1RN promotes osteoblastic differentiation via interacting with ITGB3 in osteoporosis

The occurrence and progress of osteoporosis(OP)are partially caused by impaired osteoblast differentiation.Interleukin-I receptor antagonist(IL1RN)is an immune ...     

A preliminary X-ray study of a refolded PTS EIIBfruc protein from Escherichia coli

The phosphoenolpyruvate-carbohydrate phosphotransferase system (PTS) catalyzes the phosphorylation and transportation of its sugar substrates. A sugar-specific enzyme II complex involved in the PTS finally functions to translocate substrates across the membrane. A PTS EIIB(fruc) protein, a fructose specific EIIB subunit, from Escherichia coli has been cloned, expressed, refolded, purified, and crystallized. The synchrotron data were collected to 2.6 A from the crystal of a selenomethionine substitute PTS EIIB(fruc) protein. The crystal belongs to the primitive trigonal space group P3(1)21, with unit-cell parameters of a = 33.4 A, b = 33.4 A, c = 154.0 A, and beta = 120.0 degrees . A full structure determination is under way to provide insights into the structure-function relationships of this protein.     

Determination of cefazedone in human plasma by high performance liquid chromatography–tandem mass spectrometry: Application to a pharmacokinetic study on Chinese volunteers

A rapid, sensitive and simple high performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) method was developed for determination of cefazedone in human plasma using metronidazole as internal standard (IS). The chromatographic separation was achieved on an Ultimate XB-CN column (2.1 mm × 150 mm, 5 μm) with an isocratic mobile phase of acetonitrile and 20 mM ammonium acetate in 0.1% formic acid in water (15:85, v/v). Detection was performed using electrospray ionization in positive ion multiple reaction-monitoring mode (SRM), monitoring the transitions m/z 548.2 → 344.1 for cefazedone and m/z 172.2 → 128.1 for IS. Calibration curves were linear over a wide range of 0.20–401.12 μg/mL for cefazedone in plasma. The lower limit of quantification (LLOQ) was 0.20 μg/mL. The intra- and inter-day precisions were less than 7.2%. The average recovery of cefazedone was 90.8–91.0%. The validated method was successfully applied to the pharmacokinetic study of cefazedone in Chinese healthy volunteers following intravenous (IV) administration of 500, 1000 and 2000 mg cefazedone injection.     

Invasive alien plant species in China: regional distribution patterns

Plant invasions have been attracting increasing attention from ecologists because of their worldwide environmental impacts and huge economic costs. Research on the characteristics of the recipient regions is essential for understanding the process of plant invasion. However, few previous studies on invasibility of habitats include social factors, although human activities are critical in the process of plant invasion. China is a vast country with high plant species diversity and a long history of introduction of exotic plant species and is particularly vulnerable to invasive plant species. Alien plant species are widespread in the country. Therefore, the study of invasive plants in China is urgent in practice and theoretically important for developing invasion ecology. For the present study, 126 species were selected to represent the major invasive plant species in China. We then collected data on their species richness in 31 provincial administrative units of China and performed Spearman rank correlations between species richness and possible natural and socio‐economic factors. We found that socio‐economic factors, such as human density and GDP, correlated positively with the species richness of invasive plants in China. In conjunction with the natural and socio‐economic correlations in the study of regional distribution pattern of the major invasive plants, we discussed the factors influencing the regional distribution pattern of the major invasive plants in China. We suggest that native plant species richness was mainly determined by the natural conditions of the regions, while invasive species richness was influenced by natural conditions and human disturbance together.     

The C termini of Arabidopsis cryptochromes mediate a constitutive light response

Cryptochrome blue light photoreceptors share sequence similarity to photolyases, flavoproteins that mediate light-dependent DNA repair. However, cryptochromes lack photolyase activity and are characterized by distinguishing C-terminal domains. Here we show that the signaling mechanism of Arabidopsis cryptochrome is mediated through the C terminus. On fusion with beta-glucuronidase (GUS), both the Arabidopsis CRY1 C-terminal domain (CCT1) and the CRY2 C-terminal domain (CCT2) mediate a constitutive light response. This constitutive photomorphogenic (COP) phenotype was not observed for mutants of cct1 corresponding to previously described cry1 alleles. We propose that the C-terminal domain of Arabidopsis cryptochrome is maintained in an inactive state in the dark. Irradiation with blue light relieves this repression, presumably through an intra- or intermolecular redox reaction mediated through the flavin bound to the N-terminal photolyase-like domain.     

融合基因umcel5N-CBM的构建、表达及融合酶性质分析

BM,并实现了融合基因在大肠杆菌BL21(DE3)pLysS中的表达.研究结果表明,融合酶Umcel5N-CBM与结晶纤维素(avicel)以及滤纸粉末的结合能力比原始酶Umcel5N提高了约一倍,但未显示出降解结晶纤维素的新活性,说明在结晶纤维素的降解过程中,纤维素酶的催化功能域起到关键作用.