Initial iron oxidation in horse spleen apoferritin. Characterization of a mixed-valence iron(II)-iron(III) complex.

In ferritin, iron is stored by oxidative deposition of the ferrous ion to form a hydrous ferric oxide mineral core. Two intermediates, formed during the initial stages of iron accumulation in apoferritin, have been observed previously in our laboratory and have been identified as a mononuclear Fe3(+)-protein complex and a mixed-valence Fe2(+)-Fe3(+)-protein complex. The physical characteristics of the mixed-valence Fe2(+)-Fe3+ complex and its relationship to the mononuclear Fe3+ complex in horse spleen apoferritin samples to which 0-240 iron atoms were added was examined by EPR spectroscopy. The results indicate that the mononuclear complex is not a precursor to the formation of the mixed-valence complex. Competitive binding studies with Cd2+, Zn2+, Tb3+, and UO2+(2) suggest that the mixed-valence complex is formed on the interior of the protein in the vicinity of the 2-fold axis of the subunit dimer. The mixed-valence complex could be generated by the partial oxidation of Fe2+ in apoferritin containing 120 Fe2+ or by the addition of up to 120 Fe2+ to ferritin already containing 18 Fe3+/protein molecule. The fact that the complex is generated during early Fe2+ oxidation suggests that it may be a key intermediate during the initial oxidative deposition of iron in the protein. The unusual EPR powder lineshape at 9.3 GHz of the mixed-valence complex was simulated with a rhombic g-tensor (gx = 1.95, gy = 1.88, gz = 1.77) and large linewidths and g-strain parameters. The presence of significant g-strain in the complex probably accounts for the failure to observe an EPR signal at 35 GHz and likely reflect considerable flexibility in the structure of the metal site. The temperature dependence of the EPR intensity in the range 8-38 K was modeled successfully by an effective spin Hamiltonian including exchange coupling (-2JS1.S2) and zero-field terms, from which an antiferromagnetic coupling of J = -4.0 +/- 0.5 cm-1 was obtained. This low value for J may reflect the presence of a mu-oxo bridge(s) in the dimer.     

Experimental warming and drought treatments reduce physiological activities and increase mortality of Pinus koraiensis seedlings

Plant Ecology - This study was conducted to investigate physiological responses and mortality of P. koraiensis seedlings under warming and drought treatments. In May 2016, 90 P. koraiensis...     

Inhibition of Cdc42 activity extends lifespan and decreases circulating inflammatory cytokines in aged female C57BL/6 mice

Cdc42 is a small RhoGTPase regulating multiple functions in eukaryotic cells. The activity of Cdc42 is significantly elevated in several tissues of aged mice, while the Cdc42 gain‐of‐activity mouse model presents with a premature aging‐like phenotype and with decreased lifespan. These data suggest a causal connection between elevated activity of Cdc42, aging, and reduced lifespan. Here, we demonstrate that systemic treatment of aged (75‐week‐old) female C57BL/6 mice with a Cdc42 activity‐specific inhibitor (CASIN) for 4 consecutive days significantly extends average and maximum lifespan. Moreover, aged CASIN‐treated animals displayed a youthful level of the aging‐associated cytokines IL‐1β, IL‐1α, and INFγ in serum and a significantly younger epigenetic clock as based on DNA methylation levels in blood cells. Overall, our data show that systemic administration of CASIN to reduce Cdc42 activity in aged mice extends murine lifespan.     

三种淡水鱼类在中国南北两个地区的肠道菌群差异比较

山东省德州市禹城市和湖南省长沙市望城区分别属于我国北方和南方地区,环境和气候差异明显。本试验以禹城市和望城区两地的草鱼(Ctenopharyngodon idella)、鲫鱼(Carassius auratus)和鲤鱼(Cyprinus carpio)为研究对象,对肠道中的菌群进行16s rRNA V4高变区扩增,基于IonS5 TM XL测序平台进行测序,并对相关数据进行分析。结果表明,在门水平上鲫鱼、鲤鱼、草鱼的肠道优势菌主要为变形菌门(Proteobacteria)、梭杆菌门(Fusobacteria)、硬壁菌门(Firmicutes),拟杆菌门(Bacteroidetes),各组中这四种菌门所占比之和均在80%以上;基于Bray-Curtis距离值的秩次进行组间差异显著性检验,山东草鱼组和湖南草鱼组比较中组间差异大于组内差异(R=0.307,P<0.05),且线性判别分析显示湖南草鱼组的特征性菌群为弧菌属,而山东草鱼组的为梭菌纲,推测特征性菌群差异与环境的影响有关;有害菌种的统计分析表明,湖南鲫鱼组和鲤鱼组的嗜水气单胞菌属相对丰度明显高于对应的山东鲫鱼组和鲤鱼组,山东草鱼组和鲤鱼组的弧菌属相对丰度高于对应的湖南草鱼组和鲤鱼组,可能受外界环境的影响,不同地区抵御外来有害细菌的能力也不一样。本研究对两地的淡水鱼类肠道微生物群落结构进行了比较和分析,为进一步的鱼类发育研究奠定基础。     

Multispectral canopy reflectance improves spatial distribution models of Amazonian understory species

Species distribution models are required for the research and management of biodiversity in the hyperdiverse tropical forests, but reliable and ecologically relevant digital environmental data layers are not always available. We here assess the usefulness of multispectral canopy reflectance (Landsat) relative to climate data in modelling understory plant species distributions in tropical rainforests. We used a large dataset of quantitative fern and lycophyte species inventories across lowland Amazonia as the basis for species distribution modelling (SDM). As predictors, we used CHELSA climatic variables and canopy reflectance values from a recent basin-wide composite of Landsat TM/ETM+ images both separately and in combination. We also investigated how species accumulate over sites when environmental distances were expressed in terms of climatic or surface reflectance variables. When species accumulation curves were constructed such that differences in Landsat reflectance among the selected plots were maximised, species accumulated faster than when climatic differences were maximised or plots were selected in a random order. Sixty-nine species were sufficiently frequent for species distribution modelling. For most of them, adequate SDMs were obtained whether the models were based on CHELSA data only, Landsat data only or both combined. Model performance was not influenced by species’ prevalence or abundance. Adding Landsat-based environmental data layers overall improved the discriminatory capacity of SDMs compared to climate-only models, especially for soil specialist species. Our results show that canopy surface reflectance obtained by multispectral sensors can provide studies of tropical ecology, as exemplified by SDMs, much higher thematic (taxonomic) detail than is generally assumed. Furthermore, multispectral datasets complement the traditionally used climatic layers in analyses requiring information on environmental site conditions. We demonstrate the utility of freely available, global remote sensing data for biogeographical studies that can aid conservation planning and biodiversity management.     

Compositional turnover and variation in Eemian pollen sequences in Europe

Vegetation History and Archaeobotany - The Eemian interglacial represents a natural experiment on how past vegetation with negligible human impact responded to amplified temperature changes...     

Uniparental isodisomy of chromosome 2 causing MRPL44-related multisystem mitochondrial disease

Mutations in nuclear-encoded protein subunits of the mitochondrial ribosome are an increasingly recognised cause of oxidative phosphorylation system (OXPHOS) disorders. Among them, mutations in the MRPL44 gene, encoding a structural protein of the large subunit of the mitochondrial ribosome, have been identified in four patients with OXPHOS defects and early-onset hypertrophic cardiomyopathy with or without additional clinical features. A 23-year-old individual with cardiac and skeletal myopathy, neurological involvement, and combined deficiency of OXPHOS complexes in skeletal muscle was clinically and genetically investigated. Analysis of whole-exome sequencing data revealed a homozygous mutation in MRPL44 (c.467 T?>?G), which was not present in the biological father, and a region of homozygosity involving most of chromosome 2, raising the possibility of uniparental disomy. Short-tandem repeat and genome-wide SNP microarray analyses of the family trio confirmed complete maternal uniparental isodisomy of chromosome 2. Mitochondrial ribosome assembly and mitochondrial translation were assessed in patient derived-fibroblasts. These studies confirmed that c.467 T?>?G affects the stability or assembly of the large subunit of the mitochondrial ribosome, leading to impaired mitochondrial protein synthesis and decreased levels of multiple OXPHOS components. This study provides evidence of complete maternal uniparental isodisomy of chromosome 2 in a patient with MRPL44-related disease, and confirms that MRLP44 mutations cause a mitochondrial translation defect that may present as a multisystem disorder with neurological involvement.