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81.
A dual-wavelength fluorimeter was constructed, which used two light emitting diodes (LEDs) to excite the fluorescence dye RH 421 alternately with two different wavelengths. The ratio of the emissions at the two excitation wavelengths provided a drift-insensitive signal, which allowed detection of very small changes of the fluorescence intensity. Those small changes were induced by ion binding and release in conformation E1 of the Na,K-ATPase. Titration experiments were performed to determine equilibrium dissociation constants (± standard deviation) for each step in the complete binding and release sequence: 0.12 ± 0.01 mM (E2(K2) KE1), 0.08 ± 0.01 mM (KE1 E1), 3.0 ± 0.2 mM (NaE1 E1), 5.2 ± 0.4 mM (Na2E1 NaE1) and 6.5 ± 0.4 mM (Na3E1 Na2E1) at pH 7.2 and T=16°C. These numbers show that the affinities of the binding sites exposed to the cytoplasm, are higher for K+ than for Na+ ions, similar to what was found on the extracellular side. The physiological requirement for extrusion of Na+ from the cytoplasm, and for import of K+ from the extracellular medium seems to be facilitated not by favorable binding affinities in state E1 but by the two ATP-driven reaction steps of the cycle, E2(K2) + ATP K2E1 · ATP and Na3E1 · ATP (Na3) El-P, which border the ion exchange reactions at the binding sites in conformation E1.
Correspondence to: H.-J. Apell 相似文献
82.
Effective population size as a driver for divergence of an antimicrobial peptide (Hymenoptaecin) in two common European bumblebee species 下载免费PDF全文
H. Michael G. Lattorff Mario Popp Susann Parsche Sophie Helbing Silvio Erler 《Biological journal of the Linnean Society. Linnean Society of London》2016,119(2):299-310
Social insects are the target of numerous pathogens. This is because the high density of closely‐related individuals frequently interacting with each other enhances the transmission and establishment of pathogens. This high selective pressure results in the rapid evolution of immune genes, which might be counteracted by a reduced effective population size (Ne) lowering the effectiveness of selection. We tested the effect of Ne on the evolutionary rate of an important immune gene for the antimicrobial peptide Hymenoptaecin in two common central European bumblebee species: Bombus terrestris and Bombus lapidarius. Both species are similar in their biology and are expected to be under similar selective pressures because pathogen prevalence does not differ between species. However, previous studies indicated a higher Ne in B. terrestris compared to B. lapidarius. We found high intraspecific variability in the coding sequence but low variability for silent polymorphisms in B. lapidarius. Estimates of long‐ and short‐term Ne were three‐ to four‐fold higher Ne in B. terrestris, although the species did not differ in census population sizes. The difference in Ne might result in less efficient selection and suboptimal adaptation of immune genes (e.g. hymenoptaecin) in B. lapidarius, and thus this species might become less resistant and more tolerant, turning into a superspreader of diseases. 相似文献
83.
Ornithobacterium rhinotracheale (ORT) is an economically important bacterial pathogen of turkeys and chickens worldwide. Since its first detection, a variety of typing methods have been used to gain basic knowledge about the bacterial population structure, an issue that still needs to be addressed. Serological characterization revealed at least 18 different serotypes (A-R) with ORT of serotype A to be predominate among poultry. This study aimed to establish a multilocus sequence typing (MLST) scheme for ORT that could easily be used by other laboratories and allows for worldwide comparison of sequence data. For this purpose, 87 ORT strains from different poultry hosts, geographical origins, years of isolation and serotypes were included in the analysis to identify correlations. Fourteen different sequence types (ST) were found. The most common ST1 was identified in 40 ORT strains from turkeys and chickens on 4 continents and in 3 different European countries. Together with ST9, both STs represented over three quarters (77%) of ORT strains used in the MLST analysis and included strains of frequently cross-reacting ORT serotypes A, E and I. Nine STs were only represented by one ORT strain and might indicate possible avian host, disease or serotype-specific relationships. In contrast, discrepancies between serotype and phylogenetic relatedness were clearly demonstrated by ORT strains that belonged to identical serotypes but differed in their ST. The overall identified low genetic diversity among strains isolated from turkeys and chickens independent of host and geographical origins suggests that ORT has only recently been introduced into domestic poultry and dispersed worldwide. 相似文献
84.
Claudia B?rnhorst Alfonso Siani Paola Russo Yannis Kourides Isabelle Sion Denés Molnár Luis A. Moreno Gerardo Rodríguez Yoav Ben-Shlomo Laura Howe Lauren Lissner Kirsten Mehlig Susann Regber Karin Bammann Ronja Foraita Wolfgang Ahrens Kate Tilling 《PloS one》2016,11(2)
Background
Starting from birth, this explorative study aimed to investigate between-country differences in body mass index (BMI) trajectories and whether early life factors explain these differences.Methods
The sample included 7,644 children from seven European countries (Belgium, Cyprus, Germany, Hungary, Italy, Spain, Sweden) participating in the multi-centre IDEFICS study. Information on early life factors and in total 53,409 repeated measurements of height and weight from 0 to <12 years of age were collected during the baseline (2007/2008) and follow-up examination (2009/2010) supplemented by records of routine child health visits. Country-specific BMI growth curves were estimated using fractional polynomial mixed effects models. Several covariates focussing on early life factors were added to the models to investigate their role in the between-countries differences.Results
Large between-country differences were observed with Italian children showing significantly higher mean BMI values at all ages ≥ 3 years compared to the other countries. For instance, at age 11 years mean BMI values in Italian boys and girls were 22.3 [21.9;22.8; 99% confidence interval] and 22.0 [21.5;22.4], respectively, compared to a range of 18.4 [18.1;18.8] to 20.3 [19.8;20.7] in boys and 18.2 [17.8;18.6] to 20.3 [19.8;20.7] in girls in the other countries. After adjustment for early life factors, differences between country-specific BMI curves became smaller. Maternal BMI was the factor being most strongly associated with BMI growth (p<0.01 in all countries) with associations increasing during childhood. Gestational weight gain (GWG) was weakly associated with BMI at birth in all countries. In some countries, positive associations between BMI growth and children not being breastfed, mothers’ smoking during pregnancy and low educational level of parents were found.Conclusion
Early life factors seem to explain only some of the inter-country variation in growth. Maternal BMI showed the strongest association with children’s BMI growth. 相似文献85.
Susann F. Biddulph 《Planta》1967,74(4):350-367
Summary Microautoradiographic techniques were used to determine the distribution of Ca45 and S35 in regions of the bean root where anatomical features may influence the processes of ion uptake and translocation. Root tissue from intact plants was prepared by methods that preserve both soluble and insoluble Ca and S. Ca45 distribution was determined after 1 hour and 15 min, of uptake, after 2 efflux periods, and after replacement by non-tracer Ca.S35 distribution was determined after 1 hour and 15 min of uptake.The quantity of Ca45 that entered the root was greater than the quantity of S35. Ca45 concentration within the root increased with linear distance from the 8-mm level behind the tip. The pathways of Ca and S across the cortex appeared to be different since Ca45 was particularly associated with cell walls and S35 was distributed more evenly through the cells. There was no evidence that the endodermis was a diffusion barrier for Ca; the small parenchyma cells associated with conducting elements acquired a high concentration of Ca45 and thus appear to be implicated in absorption and perhaps in transfer to the xylem. The evidence suggests that the endodermis may have been a barrier for S, but if so, certain parenchyma cells inside the stele, especially at xylem poles, were equally involved. The region from 30 to 80 mm from the tip appeared to participate in Ca uptake and transfer to the xylem; because of tissue immaturity the 8-mm region, which contained the least Ca45, was thought not to translocate to the shoot. Deposition of Ca45 in oxalate crystals represented almost complete immobilization. Calcium oxalate metabolism was most active in the 30-mm region of secondary roots and in their small branches. S35-labelled nuclei occurred in the cortex 2.5 to 3 mm behind the root tip. 相似文献
86.
87.
Phosphorylation of Mycoplasma pneumoniae cytadherence-accessory proteins in cell extracts. 总被引:2,自引:0,他引:2 下载免费PDF全文
A cell-free system was used to characterize the phosphorylation of Mycoplasma pneumoniae proteins HMW1 and HMW2, which are involved in the adherence of this organism to human tracheal epithelium during infection. The pH and cation requirements for phosphorylation of HMW1 and HMW2 were determined, and the effects of glycolytic intermediates, cyclic AMP, and eukaryotic kinase-phosphatase inhibitors and stimulators on this process were examined. Phosphoamino acid analysis identified serine as the major phosphate acceptor for both HMW1 and HMW2 in this system. 相似文献
88.
89.
Human gastric glycosphingolipids recognized by Helicobacter pylori vacuolating cytotoxin VacA 总被引:2,自引:0,他引:2
Roche N Ilver D Angström J Barone S Telford JL Teneberg S 《Microbes and infection / Institut Pasteur》2007,9(5):605-614
Many bacterial toxins utilize cell surface glycoconjugate receptors for attachment to target cells. In the present study the potential carbohydrate binding of Helicobacter pylori vacuolating cytotoxin VacA was investigated by binding to human gastric glycosphingolipids on thin-layer chromatograms. Thereby a distinct binding of the toxin to two compounds in the non-acid glycosphingolipid fraction was detected. The VacA-binding glycosphingolipids were isolated and characterized by mass spectrometry and proton NMR as galactosylceramide (Galbeta1Cer) and galabiosylceramide (Galalpha4Galbeta1Cer). Comparison of the binding preferences of the protein to reference glycosphingolipids from other sources showed an additional recognition of glucosylceramide (Glcbeta1Cer), lactosylceramide (Galbeta4Glcbeta1Cer) and globotriaosylceramide (Galalpha4Galbeta4Glcbeta1Cer). No binding to the glycosphingolipids recognized by the VacA holotoxin was obtained with a mutant toxin with deletion of the 37 kDa fragment of VacA (P58 molecule). Collectively our data show that the VacA cytotoxin is a glycosphingolipid binding protein, where the 37 kDa moiety is required for carbohydrate recognition. The ability to bind to short chain glycosphingolipids will position the toxin close to the cell membrane, which may facilitate toxin internalization. 相似文献
90.
Ionic liquids (ILs) are composed only of ions. Of special interest to this review are those where at least one ion (the cation) is organic and whose melting points are below or not far above room temperature. ILs are designated as "green" solvents because they have extremely low vapor pressure, are non-inflammable, and thermally and chemically stable. Therefore, many of them can be, in principle, recycled into the process indefinitely. The objective of the present review is to discuss different aspects of the use of ILs in carbohydrate chemistry, in particular, dissolution and functionalization of simple sugars, cyclodextrins, cellulose, starch, and chitin/chitosan. The molecular structure and synthesis of ILs most frequently employed in carbohydrate chemistry are discussed with an emphasis on imidazolium and pyridinium cations with different counterions. The physicochemical properties of ILs that are relevant to the dissolution and functionalization of carbohydrates, in particular their polarities and hydrogen-bonding abilities, are discussed. Dissolution of simple saccharides and biopolymers in ILs is presented with an emphasis on the mechanism of carbohydrate--IL interactions. Finally, the very interesting novel applications of the solutions obtained are addressed. These include, inter alia, spinning of the dissolved biopolymer into fibers, extrusion into slabs and rods, formation of matrixes for a myriad of substrates, including biomacromolecules, formation of nanocomposites, and functionalization to produce important derivatives. The use of ILs in many branches of science is expanding fast; it is hoped that this review will draw the attention of researchers to the "window of opportunities" that these green solvents open into carbohydrate chemistry. 相似文献