Viscoelastic properties of blood studied through piezoresistance measurements

Piezoresistance describes the change of electrical resistance in a material undergoing deformation. Heterogeneous materials having different resistivities of dispersed and continuous matrix phases, such as blood (comprised of red and white blood cells and platelets suspended in plasma), can exhibit the piezoresistance effect. For an initially isotropic material, two independent intrinsic material coefficients, λ1 and λ2, would uniquely describe the piezoresistance phenomenon. Materials undergoing deformation affect a material's resistivity in two ways: (a) by introducing anisotropy in the material, which is characterized by λ1 and (b) by changing the volume density of the inclusions, which is associated with (1/3?λ1+λ2). In this paper, the piezoresistance effect in bovine blood samples is studied under oscillatory shear flow with a planar sensor rosette. The first piezoresistance coefficient, λ1, was measured at various frequencies and shear rates in the blood flow and compared with cos?δ (equal to G'/G*, where G' and G* are the storage and complex moduli, respectively), which reflects the degree of elasticity. The coefficient λ1 was found to have a trend similar to that of cos?δ under all conditions tested. Thus λ1 might potentially be used to characterize the viscoelastic properties of blood and the deformability of red blood cells, thus clarifying pathophysiology and facilitating diagnosis.     

ITS1: a DNA barcode better than ITS2 in eukaryotes?

A DNA barcode is a short piece of DNA sequence used for species determination and discovery. The internal transcribed spacer (ITS/ITS2) region has been proposed as the standard DNA barcode for fungi and seed plants and has been widely used in DNA barcoding analyses for other biological groups, for example algae, protists and animals. The ITS region consists of both ITS1 and ITS2 regions. Here, a large‐scale meta‐analysis was carried out to compare ITS1 and ITS2 from three aspects: PCR amplification, DNA sequencing and species discrimination, in terms of the presence of DNA barcoding gaps, species discrimination efficiency, sequence length distribution, GC content distribution and primer universality. In total, 85 345 sequence pairs in 10 major groups of eukaryotes, including ascomycetes, basidiomycetes, liverworts, mosses, ferns, gymnosperms, monocotyledons, eudicotyledons, insects and fishes, covering 611 families, 3694 genera, and 19 060 species, were analysed. Using similarity‐based methods, we calculated species discrimination efficiencies for ITS1 and ITS2 in all major groups, families and genera. Using Fisher's exact test, we found that ITS1 has significantly higher efficiencies than ITS2 in 17 of the 47 families and 20 of the 49 genera, which are sample‐rich. By in silico PCR amplification evaluation, primer universality of the extensively applied ITS1 primers was found superior to that of ITS2 primers. Additionally, shorter length of amplification product and lower GC content was discovered to be two other advantages of ITS1 for sequencing. In summary, ITS1 represents a better DNA barcode than ITS2 for eukaryotic species.     

Nitrogen‐Doping‐Induced Defects of a Carbon Coating Layer Facilitate Na‐Storage in Electrode Materials

A nitrogen‐doped, carbon‐coated Na₃V₂(PO₄)₃ cathode material is synthesized and the formation of doping type of nitrogen‐doped in carbon coating layer is systemically investigated. Three different carbon‐nitrogen species: pyridinic N, pyrrolic N, and quaternary N are identified. The most important finding is that different carbon‐nitrogen species in the carbon layer have different impacts on the improvement of the electrochemical properties of Na₃V₂(PO₄)₃. Pyridinic N and pyrrolic N significantly increase the electronic conductivity and create numerous extrinsic defects and active sites. Quaternary N only increases the electronic conductivity without creating extrinsic defects. Therefore, it is unexpectedly demonstrated that the Na₃V₂(PO₄)₃/C+N, in which with minimize content of quaternary N or exist most extrinsic defects, exhibits the best electrochemical performance, particularly the rate performance and cycling stability. For example, when the discharging rate increased from 0.2 C to 5 C, its capacity of 101.9 mAh g^?1 decays to 84.3 mAh g^?1 and an amazing capacity retention of 83% is achieved. Moreover, even at higher current density of 5 C, an excellent capacity retention of 93% is maintained even after 100 cycles.     

Protein stabilizer,NDSB‐195, enhances the dynamics of the β4‐α2 loop of ubiquitin

Non‐detergent sulfobetaines (NDSBs) are a new group of small, synthetic protein stabilizers, which have advantages over classical compatible osmolytes, such as polyol, amines, and amino acids: they do not increase solution viscosity, unlike polyols, and they are zwitterionic at all pH ranges, unlike amines and amino acids. NDSBs also facilitate the crystallization and refolding of proteins. The mechanism whereby NDSBs exhibit such activities, however, remains elusive. To gain insight into this mechanism, we studied, using nuclear magnetic resonance (NMR), the effects of dimethylethylammonium propane sulfonate (NDSB‐195) on the dynamics of ubiquitin, on which a wealth of information has been accumulated. By analyzing the line width of amide proton resonances and the transverse relaxation rates of nitrogen atoms, we found that NDSB‐195 enhances the microsecond–millisecond dynamics of a β₄‐α₂ loop of ubiquitin. Although those compounds that enhance protein dynamics are generally considered to destabilize protein molecules, NDSB‐195 enhanced the stability of ubiquitin against guanidium chloride denaturation. Thus, the simultaneous enhancement of stability and flexibility by a single compound can be attained. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.     

CPGView: A package for visualizing detailed chloroplast genome structures

Chloroplast genomes have been widely used in studying plant phylogeny and evolution. Several chloroplast genome visualization tools have been developed to display the distribution of genes on the genome. However, these tools do not draw features, such as exons, introns, repetitive elements, and variable sites, disallowing in-depth examination of the genome structures. Here, we developed and validated a software package called Chloroplast Genome Viewers (CPGView). CPGView can draw three maps showing (i) the distributions of genes, variable sites, and repetitive sequences, including microsatellites, tandem and dispersed repeats; (ii) the structure of the cis-splicing genes after adjusting the exon-intron boundary positions using a coordinate scaling algorithm, and (iii) the structure of the trans-splicing gene rps12. To test the accuracy of CPGView, we sequenced, assembled, and annotated 31 chloroplast genomes from 31 genera of 22 families. CPGView drew maps correctly for all the 31 chloroplast genomes. Lastly, we used CPGView to examine 5998 publicly released chloroplast genomes from 2513 genera of 553 families. CPGView succeeded in plotting maps for 5882 but failed to plot maps for 116 chloroplast genomes. Further examination showed that the annotations of these 116 genomes had various errors needing manual correction. The test on newly generated data and publicly available data demonstrated the ability of CPGView to identify errors in the annotations of chloroplast genomes. CPGView will become a widely used tool to study the detailed structure of chloroplast genomes. The web version of CPGView can be accessed from http://www.1kmpg.cn/cpgview .     

Activation of <Emphasis Type="Italic">Helicobacter pylori</Emphasis> inorganic pyrophosphatase and the importance of Cys16 in thermostability,enzyme activation and quaternary structure

The inorganic pyrophosphatase from the human pathogen Helicobacter pylori (HpPPase) is a family I PPase. It is a homohexamer consisting of identical 20-kDa subunits. Hydrolysis of inorganic pyrophosphate (PP_i) by HpPPase relied on the presence of magnesium and followed Michaelis–Menten kinetics, with k _cat being 344 s⁻¹ and K _m being 83 μM at pH 8.0, which was the optimal pH for catalysis. HpPPase was activated by both thiol and non-thiol reductants, distinct from the previously suggested inactivation/reactivation process involving formation and breakage of disulfide bonds. Substitution of Cys16 of HpPPase, which was neither located at the active site nor evolutionarily conserved, resulted in a loss of 50% activity and a reduction in sensitivity to reductants and oxidized glutathione. In addition, the C16S replacement caused a considerable disruption in thermostability, which exceeded that resulted from active-site mutations such as Y140F HpPPase and those of Escherichia coli. Although Cys16 was not located at the subunit interface of the hexameric HpPPase, sedimentation analysis results suggested that the C16S substitution destabilized HpPPase through impairing trimer–trimer interactions. This study provided the first evidences that the single cysteine residue of HpPPase was involved in enzyme activation, thermostability, and stabilization of quaternary structure. Mon-Juan Lee and Haimei Huang contributed equally to this work.     

Crystal structure of Helicobacter pylori spermidine synthase: a Rossmann-like fold with a distinct active site

Spermidine synthase (putrescine aminopropyltransferase, PAPT) catalyzes the transfer of the aminopropyl group from decarboxylated S-adenosylmethionine to putrescine during spermidine biosynthesis. Helicobacter pylori PAPT (HpPAPT) has a low sequence identity with other PAPTs and lacks the signature sequence found in other PAPTs. The crystal structure of HpPAPT, determined by multiwavelength anomalous dispersion, revealed an N-terminal beta-stranded domain and a C-terminal Rossmann-like domain. Structural comparison with other PAPTs showed that HpPAPT has a unique binding pocket between two domains, numerous non-conserved residues, a less acidic electrostatic surface potential, and a large buried space within the structure. HpPAPT lacks the gatekeeping loop that facilitates substrate binding in other PAPTs. PAPTs are essential for bacterial cell viability; thus, HpPAPT may be a potential antimicrobial drug target for H. pylori owing to its characteristic PAPT sequence and distinct conformation.     

加味四君子汤对脾虚胃溃疡大鼠细胞外信号调节激酶信号传递分子的影响

目的探讨加味四君子汤治疗脾虚证的机理。方法运用HE染色显示胃组织结构,运用免疫组织化学方法显示下颌下腺EGF含量的变化,运用免疫印迹法显示胃黏膜ERK2含量的变化。结果经过加味四君子汤治疗后,脾虚胃溃疡大鼠下颌下腺颗粒曲管细胞内EGF阳性反映产物的含量减少,胃黏膜磷酸化的ERK2增加,胃溃疡愈合加快;而自然恢复组上述变化不明显。结论加味四君子汤可能通过影响分裂原激活的蛋白激酶信号传递途径而发挥治疗作用。     

Arsenite induces apoptosis in chinese hamster ovary cells by generation of reactive oxygen species

Arsenic, a human carcinogen, possesses a serious environmental threat but the mechanism of its toxicity remains unclear. Knowledge of how arsenic induces cell death and how cells escape the death path may help to understand arsenic carcinogenesis. We have investigated the nature of sodium arsenite-induced cell death in Chinese hamster ovary K1 cells. Following phosphate-citric acid buffer extraction, apoptotic cells with lower DNA content than the G1 cells were detected by flow cytometry. Immediately after 4 h of 40 μM arsenite treatment, no appreciable fraction of cells with sub-G1 DNA content was detected; however, the sub-G1 cell fraction increased with postarsenite incubation time, and detectable increase started at 8 h of incubation, whereas the intracellular peroxide level as measured by the fluorescent intensity of 2′,7′-dichlorofluorescein increased immediately following a 4-h arsenite treatment. Simultaneous treatment with arsenite plus antioxidant (N-acetyl-cysteine, Trolox, and Tempo); copper ion chelator (neocuproine); protein kinase inhibitor (H-7) or protein synthesis inhibitor (cycloheximide) reduced the fraction of sub-G1 cell and internucleosomal DNA degradation. Trolox, neocuproine, or cycloheximide given after arsenite treatment also effectively reduced apoptosis. These results lead to a working hypothesis that arsenite-induced apoptosis in CHO-K1 cells is triggered by the generation of hydrogen peroxide, followed by a copper-mediated Fenton reaction that catalyzes the production of hydroxyl radicals, which selectively activates protein kinase through de novo synthesis of macromolecules. © 1996 Wiley-Liss, Inc.