Prediction of electrostatic effects of engineering of protein charges

Accurate prediction of electrostatic effects on catalytic activity is an essential component of protein design. Site-directed mutagenesis of charged groups in subtilisin of Bacillus amyloliquefaciens has provided experimental measurements of electrostatic interactions which may be used to test such theoretical methods. The pKa of the histidine of the active site has been perturbed by +0.08 to -1.0 units by modifying one or two residues. Electrostatic effects in proteins can be modelled by the algorithm of Warwicker and Watson, which uses classical electrostatics and considers both the charge position and the shape of the molecule. Here we report that the algorithm can model several pKa shifts in subtilisin to fair accuracy.     

Mutations in LRP2, which encodes the multiligand receptor megalin, cause Donnai-Barrow and facio-oculo-acoustico-renal syndromes

Donnai-Barrow syndrome is associated with agenesis of the corpus callosum, congenital diaphragmatic hernia, facial dysmorphology, ocular anomalies, sensorineural hearing loss and developmental delay. By studying multiplex families, we mapped this disorder to chromosome 2q23.3-31.1 and identified LRP2 mutations in six families with Donnai-Barrow syndrome and one family with facio-oculo-acoustico-renal syndrome. LRP2 encodes megalin, a multiligand uptake receptor that regulates levels of diverse circulating compounds. This work implicates a pathway with potential pharmacological therapeutic targets.     

论文-引文矩阵及其推导的定量评价指标

对论文－引文矩阵的主要数据进行了分析,分析了影响因子的定义,指出了同时影响因子和历时影响因子的判别,并且讨论了使用两种影响因子进行科研评价的优缺点,建议将历时影响因子作为测度值,与被评价论文的预期影响因子,即学科引文分值进行比较。     

利用简化空气质量模型快速构建臭氧生成等浓度曲线及其应用

提出一种快速构建臭氧生成等浓度曲线的新方法.该方法利用区域空气质量模式进行臭氧前体物的敏感性分析,基于一阶和二阶敏感性系数构建简化模型,快速计算前体物不同排放水平对应的臭氧生成浓度.使用该方法,结合调整的源排放清单,对2018年8月成都平原地区进行臭氧回溯模拟并绘制臭氧生成等浓度曲线图.在此基础上,以成都市为例,对城市...     

Generation time and temporal scaling of bird population dynamics

Theoretical studies have shown that variation in density regulation strongly influences population dynamics, yet our understanding of factors influencing the strength of density dependence in natural populations still is limited. Consequently, few general hypotheses have been advanced to explain the large differences between species in the magnitude of population fluctuations. One reason for this is that the detection of density regulation in population time series is complicated by time lags induced by the life history of species that make it difficult to separate the relative contributions of intrinsic and extrinsic factors to the population dynamics. Here we use population time series for 23 bird species to estimate parameters of a stochastic density-dependent age-structured model. We show that both the strength of total density dependence in the life history and the magnitude of environmental stochasticity, including transient fluctuations in age structure, increase with generation time. These results indicate that the relationships between demographic and life-history traits in birds translate into distinct population dynamical patterns that are apparent only on a scale of generations.     

Forgery: 'fingerprinting' documents and packaging

We have found that almost all paper documents, plastic cards and product packaging contain a unique physical identity code formed from microscopic imperfections in the surface. This covert 'fingerprint' is intrinsic and virtually impossible to modify controllably. It can be rapidly read using a low-cost portable laser scanner. Most forms of document and branded-product fraud could be rendered obsolete by use of this code.     

Spin transition of iron in magnesiowüstite in the Earth's lower mantle

Iron is the most abundant transition-metal element in the mantle and therefore plays an important role in the geochemistry and geodynamics of the Earth's interior. Pressure-induced electronic spin transitions of iron occur in magnesiowüstite, silicate perovskite and post-perovskite. Here we have studied the spin states of iron in magnesiowüstite and the isolated effects of the electronic transitions on the elasticity of magnesiowüstite with in situ X-ray emission spectroscopy and X-ray diffraction to pressures of the lowermost mantle. An observed high-spin to low-spin transition of iron in magnesiowüstite results in an abnormal compressional behaviour between the high-spin and the low-spin states. The high-pressure, low-spin state exhibits a much higher bulk modulus and bulk sound velocity than the low-pressure, high-spin state; the bulk modulus jumps by approximately 35 percent and bulk sound velocity increases by approximately 15 percent across the transition in (Mg0.83,Fe0.17)O. Although no significant density change is observed across the electronic transition, the jump in the sound velocities and the bulk modulus across the transition provides an additional explanation for the seismic wave heterogeneity in the lowermost mantle. The transition also affects current interpretations of the geophysical and geochemical models using extrapolated or calculated thermal equation-of-state data without considering the effects of the electronic transition.