A 3-D electrostatic density map generated using the Wavefront Topology System and Finite Element Method clearly demonstrates the non-uniformity and periodicity present in even a single loop of an α-helix. The four di...A 3-D electrostatic density map generated using the Wavefront Topology System and Finite Element Method clearly demonstrates the non-uniformity and periodicity present in even a single loop of an α-helix. The four dihedral angles (N-C*-C-N, C*-C-N-C*, and C-N-C*-C) fully define a helical shape independent of its length: the three dihedral angles, φ = -33.5°, ω = 177.3°, and Ψ = -69.4°, generate the precise (and identical) redundancy in a one loop (or longer) α-helical shape (pitch = 1.59 /residue;r = 2.25 ). Nevertheless the pattern of dihedral angles within an 11 and a 22-peptide backbone atom sequence cannot be distributed evenly because the stoichiometry in fraction of four atoms never divides evenly into 11 or 22 backbone atoms. Thus, three sequential sets of 11 backbone atoms in an α-helix will have a discretely different chemical formula and correspondingly different combinations of molecular forces depending upon the assigned starting atom in an 11-step sequence. We propose that the unit cell of one loop of an α-helix occurs in the peptide backbone sequence C-(N-C*-C)3-N which contains an odd number of C* plus even number of amide groups. A two-loop pattern (C*-C-N)7-C* contains an even number of C* atoms plus an odd number of amide groups. Dividing the two-loop pattern into two equal lengths, one fraction will have an extra half amide (N-H) and the other fraction will have an extra half amide C=O, i.e., the stoichiometry of each half will be different. Also, since the length of N-C*-C-N, C*-C-N-C*, and C-N-C*-C are unequal, the summation of the number of each in any fraction of n loops of an α-helix in sequence will always have unequal length, depending upon the starting atom (N, C*, or C).展开更多
The Xianshuihe fault（XSHF） zone, characterized by intense tectonic activity, is located at the southwest boundary of the Bayan Har block, where several major earthquakes have occurred, including the 2008 Wenchuan an...The Xianshuihe fault（XSHF） zone, characterized by intense tectonic activity, is located at the southwest boundary of the Bayan Har block, where several major earthquakes have occurred, including the 2008 Wenchuan and the 2013 Lushan earthquakes. This study analysed underground temperature sequence data for four years at seven measuring points at different depths（maximum depth： 18.9 m） in the southeastern section of the XSHF zone. High-frequency atmospheric noise was removed from the temperature sequences to obtain relatively stable temperature fields and heat fluxes near the measurement points. Our measurements show that the surrounding bedrock at（the seven stations distributed in the fault zone） had heat flux values range from-41.0 to 206 m W/m^2, with a median value of 54.3 m W/m^2. The results indicate a low heat flux in the northern section of DaofuKangting and a relatively high heat flux in the southern section of Kangting, which is consistent with the temperature distributions of the hot springs near the fault. Furthermore, our results suggest that the heat transfer in this field results primarily from stable underground heat conduction. In addition, the underground hydrothermal activity is also an obvious factor controlling the geothermal gradient.展开更多
The soils of the semi-arid Sudano-Sahelian region of West Africa have been identified as being highly vulnerable to soil degradation with impacts on their capacity to provide goods and services in which soil microorga...The soils of the semi-arid Sudano-Sahelian region of West Africa have been identified as being highly vulnerable to soil degradation with impacts on their capacity to provide goods and services in which soil microorganisms participate. Unfortunately, soil microbial diversity from this semi-arid region with high rainfall variability remains largely unexplored. The aim of the present study was to characterize the diversity and composition of the soil bacterial communities and to identify factors involved in their spatial distribution along an environmental gradient in Senegal. Samples were collected from non-anthropogenic sites across four pedoclimatic zones. Bacterial communities were characterized using next-generation sequencing and soil physico-chemical parameters were determined. Our results showed that Firmicutes, Actinobacteria, Proteobacteria, Chloroflexi, Gemmatimonadetes, Acidobacteria, and Verrucomicrobia phyla were predominant in the soils of the region. Bacterial α-diversity was stable along the environmental gradient whereas β-diversity highlighted significant changes in the composition of the soil bacterial community. Changes were driven by shifts in the relative abundance of OTUs belonging mainly to the genus Bacillus, Conexibacter, Kaistobacter, Solirubrobacter, Ktedonobacter, Sphingomonas, Microvirga, Rubrobacter and Pelobacter. Soil properties like pH, soil moisture and clay content were the environmental parameters identified as drivers of the composition of the bacterial communities in the semi-arid Sudano-Sahelian region of Senegal (West Africa).展开更多
作为我国传统的发酵食品,腊鱼因具有独特的滋味和口感而深受人们青睐。以16 s rDNA基因为标靶,采用聚合酶链式反应-变性梯度凝胶电泳(PCR-DGGE)与Mi Seq高通量测序技术相结合的方法对采集自恩施地区腊鱼样品的细菌多样性进行了研究。PCR...作为我国传统的发酵食品,腊鱼因具有独特的滋味和口感而深受人们青睐。以16 s rDNA基因为标靶,采用聚合酶链式反应-变性梯度凝胶电泳(PCR-DGGE)与Mi Seq高通量测序技术相结合的方法对采集自恩施地区腊鱼样品的细菌多样性进行了研究。PCR-DGGE结果表明,腊鱼样品中的细菌以Psychrobacter和Lactobacillus为主。Mi Seq高通量测序结果表明,腊鱼中的优势细菌门主要为变形菌门(Proteobacteria)、硬壁菌门(Firmicutes)、拟杆菌门(Bacteroidetes)和放线菌门(Actinobacteria),其平均相对含量分别为61.29%、30.21%、5.34%和1.74%。腊鱼中的优势细菌主要为Psychrobacter、Brochothrix、Pseudomonas、Staphylococcus、Acinetobacter、Vibrio、Pseudoalteromonas和Chryseobacterium,其平均相对含量为35.70%、19.74%、7.13%、7.12%、4.19%、3.90%、3.09%和1.98%。在分类操作单元(Operational taxonomic units,OTU)水平上,发现了64个核心OTU,累计平均相对含量高达62.67%。由此可见,恩施地区腊鱼中的优势细菌主要由隶属于Proteobacteria的Psychrobacter及隶属于Firmicutes的Brochothrix构成,且不同样品共有大量的核心细菌菌群。展开更多
文摘A 3-D electrostatic density map generated using the Wavefront Topology System and Finite Element Method clearly demonstrates the non-uniformity and periodicity present in even a single loop of an α-helix. The four dihedral angles (N-C*-C-N, C*-C-N-C*, and C-N-C*-C) fully define a helical shape independent of its length: the three dihedral angles, φ = -33.5°, ω = 177.3°, and Ψ = -69.4°, generate the precise (and identical) redundancy in a one loop (or longer) α-helical shape (pitch = 1.59 /residue;r = 2.25 ). Nevertheless the pattern of dihedral angles within an 11 and a 22-peptide backbone atom sequence cannot be distributed evenly because the stoichiometry in fraction of four atoms never divides evenly into 11 or 22 backbone atoms. Thus, three sequential sets of 11 backbone atoms in an α-helix will have a discretely different chemical formula and correspondingly different combinations of molecular forces depending upon the assigned starting atom in an 11-step sequence. We propose that the unit cell of one loop of an α-helix occurs in the peptide backbone sequence C-(N-C*-C)3-N which contains an odd number of C* plus even number of amide groups. A two-loop pattern (C*-C-N)7-C* contains an even number of C* atoms plus an odd number of amide groups. Dividing the two-loop pattern into two equal lengths, one fraction will have an extra half amide (N-H) and the other fraction will have an extra half amide C=O, i.e., the stoichiometry of each half will be different. Also, since the length of N-C*-C-N, C*-C-N-C*, and C-N-C*-C are unequal, the summation of the number of each in any fraction of n loops of an α-helix in sequence will always have unequal length, depending upon the starting atom (N, C*, or C).
基金supported by the National Natural Science Foundation of China (NSFC) (Grant No.4147408641174084)+2 种基金the CAS/CAFEA international partnership program for creative research teams (KZZD-EW-TZ-19)funded by the Special Fund for Seismic Scientific Research (200808011,2004DIB3J1290)the State Key Laboratory of Earthquake Dynamics,Institute of Geology (LED2009A07)
文摘The Xianshuihe fault（XSHF） zone, characterized by intense tectonic activity, is located at the southwest boundary of the Bayan Har block, where several major earthquakes have occurred, including the 2008 Wenchuan and the 2013 Lushan earthquakes. This study analysed underground temperature sequence data for four years at seven measuring points at different depths（maximum depth： 18.9 m） in the southeastern section of the XSHF zone. High-frequency atmospheric noise was removed from the temperature sequences to obtain relatively stable temperature fields and heat fluxes near the measurement points. Our measurements show that the surrounding bedrock at（the seven stations distributed in the fault zone） had heat flux values range from-41.0 to 206 m W/m^2, with a median value of 54.3 m W/m^2. The results indicate a low heat flux in the northern section of DaofuKangting and a relatively high heat flux in the southern section of Kangting, which is consistent with the temperature distributions of the hot springs near the fault. Furthermore, our results suggest that the heat transfer in this field results primarily from stable underground heat conduction. In addition, the underground hydrothermal activity is also an obvious factor controlling the geothermal gradient.
文摘The soils of the semi-arid Sudano-Sahelian region of West Africa have been identified as being highly vulnerable to soil degradation with impacts on their capacity to provide goods and services in which soil microorganisms participate. Unfortunately, soil microbial diversity from this semi-arid region with high rainfall variability remains largely unexplored. The aim of the present study was to characterize the diversity and composition of the soil bacterial communities and to identify factors involved in their spatial distribution along an environmental gradient in Senegal. Samples were collected from non-anthropogenic sites across four pedoclimatic zones. Bacterial communities were characterized using next-generation sequencing and soil physico-chemical parameters were determined. Our results showed that Firmicutes, Actinobacteria, Proteobacteria, Chloroflexi, Gemmatimonadetes, Acidobacteria, and Verrucomicrobia phyla were predominant in the soils of the region. Bacterial α-diversity was stable along the environmental gradient whereas β-diversity highlighted significant changes in the composition of the soil bacterial community. Changes were driven by shifts in the relative abundance of OTUs belonging mainly to the genus Bacillus, Conexibacter, Kaistobacter, Solirubrobacter, Ktedonobacter, Sphingomonas, Microvirga, Rubrobacter and Pelobacter. Soil properties like pH, soil moisture and clay content were the environmental parameters identified as drivers of the composition of the bacterial communities in the semi-arid Sudano-Sahelian region of Senegal (West Africa).
