Adaptation of class-13 alpha-amylases to diverse living conditions

There are currently 35 available nonredundant molecular structures of class-13 alpha-amylases (EC 3.2.1.1), mostly from microbial organisms living under a wide range of environmental conditions. One of the most recent additions has been the first alpha-amylase structure of a hyperthermophilic archaeon [Linden et al., J. Biol. Chem. 2003, 278, 9875-9884]. The structure has been used for comparative analyses with a representative set of three alpha-amylases from thermophilic, mesophilic and psychrophilic sources to identify molecular parameters for environmental adaptation. Our analysis supports generally observed trends such as an increase in structural compactness as well as an increase in salt bridges in order to cope with high-temperature conditions. The two representative thermophilic structures used in this comparative study have independently evolved di-metal centres--not present in the mesophilic and psychrophilic structures--in the vicinity of the active site. These observations may provide impetus for the design of alpha-amylases with improved molecular properties to enhance their utility in biotechnological processes.     

紫外分光光度法测定粮食中微量铁

根据铁(Ⅲ)同磺基水扬酸形成络合物在紫外光区有较强吸收,应用紫外分光光度法测定了小麦和稻米中铁的含量。对两种消化方法—干法和湿法进行了比较,其标准偏差在0.023～0.32之间,变异系数为0.16％～1.5％,回收率达86％～103％。方法简便、快速、无需分离,结果良好。     

Surfactant-free Pd–Fe nanoparticles supported on reduced graphene oxide as nanocatalyst for formic acid oxidation

Herein, a novel surfactant-free nanocatalyst of Pd–Fe bimetallic nanoparticles (NPs) supported on the reduced graphene oxide (Pd–Fe/RGO) were synthesized using a two-step reduction in aqueous phase. Electrochemical studies demonstrate that the nanocatalyst exhibits superior catalytic activity towards the formic acid oxidation with high stability due to the synergic effect of Pd–Fe and RGO. The optimized Pd–Fe/RGO (Pd:Fe = 1:5) nanocatalyst possess an specific activity of 2.72 mA cm^?2 and an mass activity of 1.0 A mg^?1_(Pd), which are significantly higher than those of Pd/RGO and commercial Pd/C catalysts.     

Role of dietary lignans in the reduction of breast cancer risk

Lignans are a large group of fiber-associated phenolic compounds widely distributed in edible plants. Some of the ingested plant lignans are converted by intestinal microbiota to enterolignans, enterodiol (END) and enterolactone (ENL), the latter of which has been thought to be the major biologically active lignan, and suggested to be associated with low risk of breast cancer. In line with this, administration of plant lignans which are further metabolized to ENL, or ENL as such, have been shown to inhibit or delay the growth of experimental mammary cancer. The mechanism of anticarcinogenic action of ENL is not yet fully understood, but there is intriguing evidence for ENL as a modulator of estrogen signaling. These findings have generated interest in the use of lignans as components of breast cancer risk reducing functional foods. Identification of target groups, who would benefit most, is of pivotal importance. Therefore, further identification and validation of relevant biomarkers, which can be used as indicators of lignan or ENL action and breast cancer risk reduction at different stages of the disease, are of importance.     

低值海参促进小鼠骨折愈合及机制研究

海地瓜是产自东南沿海的一种低值海参,具有降血糖,降血脂,抗氧化等活性,而其对骨折愈合的研究尚未见报道.对8周龄雌性C57BL/6小鼠进行右侧胫骨开放性骨折手术构建骨折模型,在模型小鼠灌胃海地瓜(500 mg/kg BW)后的第5,10,21天取材,检测各组血清指标、组织形态学、软骨内成骨关键基因的转录水平,探究海地瓜对...     

Robust traveling salesman problem with drone: balancing risk and makespan in contactless delivery

The spread of COVID-19 outbreak has promoted truck-drone delivery from trials to commercial applications in end-to-end contactless solutions. To fully integrate truck-drone delivery in contactless solutions, we introduce the robust traveling salesman problem with a drone, in which a drone makes deliveries and returns to the truck that is moving on its route under uncertainty. The challenge is to find, for each customer location in truck-drone routing, an assignment to minimize the expected makespan. Apart from the complexity of this problem, the risk of synchronization failure associated with uncertain travel time should be also considered. The problem is first formulated as a robust model, and a novel efficient frontier heuristic is proposed to solve this model. By coupling the implicit adaptive weighting with epsilon-constraint methods, the heuristic generates a series of scalarized single-objective problems, where the goal is to minimize expected makespan under the constraint of synchronization risk. The experiment results show that the robust (near-)optimal solutions offer a considerable reduction in risk, yet only hint at a small increase in makespan. The heuristic in the present study is effective to construct approximations of Pareto frontier and allows for assignment decisions in a priori or a posteriori manner.