分类: 生物学 >> 生物物理学 >> 生物物理、生物化学与分子生物学 提交时间: 2016-05-11
摘要: It has been established that exposure in the hypomagnetic field (HMF), which is one of the environmental factor of outer space, has adverse effects on animal and human behavior and brain function. Thus, it is necessary to develop appropriate counteract strategy to avoid the HMF-induced risks to the health of the astronauts during long-term and long-distance manned space mission. However, the physical and mental effects of the HMF in details still await systematic evaluation and the underlying mechanism remains elusive, so far. In this study, we constructed an HMF animal rearing system (<500 nT) and examined the effects of one-month HMF exposure on the circadian behavior, pain response and emotions in adult male C57BL/6 mice (4 similar to 6 weeks old, (20 +/- 2) g). The control animals were reared in the geomagnetic field (GMF). The HMF-exposed animals exhibited a prolonged alteration of the circadian drinking rhythm and a decrease in general activity, accompanied with an increase in thermal hyperalgesia. But the HMF did not induce obvious depression-like and anxiety-related behaviors. The serum noradrenalin concentration in HMF-exposed mice significantly decreased. These findings indicate that the HMF disturbs the behavior rhythm and the function of endocrine system, which probably leads to the subsequently weakened activities of the animal.
分类: 生物学 >> 生物物理学 >> 生物物理、生物化学与分子生物学 提交时间: 2016-05-11
摘要: A cinetobacter baumannii is a new threat in intensive care units (ICUs) for its multiresistance to antibiotics, but little is known about this bacterium. Nucleoside diphosphate kinase (NDK) is an evolutionarily conserved enzyme that catalyzes phosphoryl transformation between nucleosides. In our study, the crystal structure of wild type A cinetobacter baumannii NDK along with its mutant generated through truncation of the C-terminal arginine-threonine-arginine (RTR) residues, were solved. In comparison with Myxococcus xanthus NDK structure, we speculated that A cinetobacter baumannii NDK shared a similar catalytic mechanism with Myxococcus xanthus. Activity assay and CD spectra analysis revealed that E28A mutant might interrupt the secondary structure of the protein leading to declined enzymatic activity. Truncation of the C-terminal RTR residues would lead to the instability of the tertiary structure resulting in reduced kinase activity. Lys33 was a key residue for maintaining dimer interaction when RTR residues were truncated but was not sufficient to keep efficient enzymatic reaction. The structural data can provide a potential target to develop novel therapeutic approaches to overcome multiresistance of the bacterium against antibiotics.