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81.
Scheen AC Pfeil BE Petri A Heidari N Nylinder S Oxelman B 《Molecular ecology resources》2012,12(1):128-135
Direct Sanger sequencing of polymerase chain reaction (PCR)-amplified nuclear genes leads to polymorphic sequences when allelic variation is present. To overcome this problem, most researchers subclone the PCR products to separate alleles. An alternative is to directly sequence the separate alleles using allele-specific primers. We tested two methods to enhance the specificity of allele-specific primers for use in direct sequencing: using short primers and amplification refractory mutation system (ARMS) technique. By shortening the allele-specific primer to 15-13 nucleotides, the single mismatch in the ultimate base of the primer is enough to hinder the amplification of the nontarget allele in direct sequencing and recover only the targeted allele at high accuracy. The deliberate addition of a second mismatch, as implemented in the ARMS technique, was less successful and seems better suited for allele-specific amplification in regular PCR rather than in direct sequencing. 相似文献
82.
83.
Complete assignment of the (1)H and (13)C NMR spectra of all possible d-glucopyranosyl-d-glucopyranosides was performed and the (1)H chemical shifts and proton-proton coupling constants were refined by computational spectral analyses (using PERCH NMR software) until full agreement between the calculated and experimental spectra was achieved. To support the experimental results, the (1)H and (13)C chemical shifts and the spin-spin coupling constants between the non-hydroxyl protons of alpha- and beta-d-glucopyranose (1a and 1b) were calculated with density functional theory (DFT) methods at the B3LYP/pcJ-2//B3LYP/6-31G(d,p) level of theory. The effects of different glycosidic linkage types and positions on the glucose ring conformations and on the alpha/beta-ratio of the reducing end hydroxyl groups were investigated. Conformational analyses were also performed for anomerically pure forms of methyl d-glucopyranosides (13a and 13b) and fully protected derivatives such as 1,2,3,4,6-penta-O-acetyl-d-glucopyranoses (14a and 14b). 相似文献
84.
Lipid-free NisI: interaction with nisin and contribution to nisin immunity via secretion 总被引:1,自引:0,他引:1
Timo M. Takala Olli Koponen Mingqiang Qiao Per E.J. Saris 《FEMS microbiology letters》2004,237(1):171-177
Nisin-producing Lactococcus lactis cells protect their own cytoplasmic membrane by specific immunity proteins, NisF/E/G and NisI, a transporter complex and a lipoprotein, respectively. A portion of NisI is secreted to the medium in a lipid-free form (LF-NisI). Here, kinetics of the interaction between nisin and LF-NisI was examined by surface plasmon resonance analysis. The affinity constant KD for the interaction was calculated to be in the micromolar range. Contribution of the secreted LF-NisI to nisin immunity was studied by replacing the lipoprotein specific nisI signal sequence with a secretion signal of non-lipoprotein origin. Secretion of LF-NisI in NisF/E/G-expressing L. lactis strain NZ9840 increased significantly its nisin tolerance suggesting that the lipid-free form of NisI could have a supportive role in nisin immunity. 相似文献
85.
Bojan Kozlev?ar Ivan Leban Saša Petri?ek Jan Reedijk 《Inorganica chimica acta》2004,357(14):4220-4230
A series of compounds of formula [{Cu2(OOCCmH2m + 1)4(urea)}2] (m=5-11) have been characterized. X-ray structure analysis for the hexanoate compound reveals a new type of tetranuclear dicopper(II) tetracarboxylate, where the central coordination sphere in [{Cu2(OOCC5H11)4(urea)}2] is composed of two dinuclear dicopper tetracarboxylates, connected via two inter-dinuclear Cu-O coordination bonds at a distance 2.222(2) Å through the apical positions of two dimers. Urea molecules (Cu-O 2.114(2) Å) occupy both outside apical positions of the resulting tetranuclear units. A strong antiferromagnetic behaviour has been shown for [{Cu2(OOCC5H11)4(urea)}2] (−2J=261.4(4) cm−1), and compared with related isolated dinuclear and polymeric hexanoate compounds [Cu2(OOCC5H11)4(urea)2], [Cu2(OOCC5H11)4]n, respectively. Only small differences in the magnetic susceptibility have been found, while EPR spectroscopy showed significantly different results for all three hexanoate compounds, also with the dicopper tetracarboxylate central core and square-pyramidal CuO4O chromophores. A solid-to-solid phase transition for [{Cu2(OOCC5H11)4(urea)}2] was observed by magnetic measurement and analysed for the whole series [{Cu2(OOCCmH2m + 1)4(urea)}2] by TG, DTA, and variable temperature XRD studies. 相似文献
86.
D'Ulivo L Chen J Meinander K Oörni K Kovanen PT Riekkola ML 《Analytical biochemistry》2008,383(1):38-43
An electrochromatographic method was developed for the in situ delipidation of intact low-density lipoprotein (LDL) particles immobilized on the inner wall of a 50-μm inner diameter silica capillary. In this method, the immobilized LDL particles were delipidated with nonionic surfactant Nonidet P-40 at pH 7.4 and 25 °C, resulting in an apolipoprotein B-100 (apoB-100)-coated capillary surface. The mobility of the electroosmotic flow marker dimethyl sulfoxide gave information about the surface charge, and the retention factors of β-estradiol, testosterone, and progesterone were informative of the surface hydrophobicity. The calculated distribution coefficients of the steroids produced specific information about the affinity interactions of the steroids, with capillary surfaces coated either with intact LDL particles or with apoB-100. Delipidation with Nonidet P-40 resulted in a strong decrease in the hydrophobicity of the LDL coating. Atomic force microscopy images confirmed the loss of lipids from the LDL particles and the presence of apoB-100 protein coating. The in situ delipidation of LDL particles in capillaries represents a novel approach for the isolation of immobilized apoB-100 and for the determination of its pI value. The technique requires extremely low quantities of LDL particles, and it is simple and fast. 相似文献
87.
Habitat characteristics and macroinvertebrate assemblages in boreal forest streams: relations to catchment silvicultural activities 总被引:2,自引:0,他引:2
Petri Liljaniemi Kari-Matti Vuori Boris Ilyashuk Hannu Luotonen 《Hydrobiologia》2002,474(1-3):239-251
We compared the stream habitat characteristics and macroinvertebrate assemblages of boreal headwater streams in both the Finnish and the Russian parts of a single river basin, the Koitajoki River. Over the last 50 years, the Finnish side of the catchment has been managed using modern forestry techniques, whereas Russian side has remained nearly unexploited and is near to its natural state. Differences in silvicultural activities were observed to contribute to differences in habitat structure. The channel habitats were in fairly natural state in the Russian reference streams, whereas the impacted Finnish sites were cleared and straightened. In comparison with the impacted channels, the abundance of coarse woody debris (CWD) was 10–100-fold higher in the reference streams. Implications on the forestry-induced deterioration of water quality were also observed. On the contrary, only small differences in macroinvertebrate assemblages were detected. Despite the lower amount of retentive structures (CWD), significantly higher relative abundance of shredders was observed in the forestry-impacted streams. Otherwise the zoobenthic communities were quite similar in the two subcatchments. We suggest that several mechanisms may explain this similarity: (1) community structure is controlled by naturally acidic conditions, (2) the adverse impacts of forestry on habitat structure and water quality of streams may be compensated by increased input of deciduous litter and organic compounds from drained, structurally young riparian forests and (3) macroinvertebrate species have flexible feeding habits and may thus readily adapt to changing conditions. 相似文献
88.
Are biological classifications of headwater streams concordant across multiple taxonomic groups? 总被引:11,自引:1,他引:10
Riku Paavola Timo Muotka Risto Virtanen Jani Heino Petri Kreivi 《Freshwater Biology》2003,48(10):1912-1923
1. Studies assessing human impacts on freshwater ecosystems are typically based on a single taxonomic group, often macroinvertebrates or fish. Unfortunately, the degree to which such macroinvertebrate or fish‐based surveys can be generalised across other taxonomic groups remains largely unknown. A prerequisite for useful generalisations is that different taxonomic groups exhibit concordant patterns of community structure across sites. 2. We examined the concordance among fish, benthic macroinvertebrates and bryophytes in 32 streams in a boreal catchment in Finland. Our goal was to test how consistently different taxonomic groups classify stream sites; for example, can site groupings based on macroinvertebrates be used as a surrogate for bryophyte or fish assemblage classification? 3. Our results show that community classifications in headwater streams are not concordant across taxonomic groups, at least not at the within‐river system scale. The lack of concordance reflected the fact that all three groups responded to different environmental factors. Macroinvertebrate community structure was mainly correlated with stream size and pH, whereas bryophytes were related to water colour, nutrient content and in‐stream habitat variability. Fish community structure was best described by stream depth, substrate size and water oxygen concentration. 4. Our results suggest that great care should be taken when typologies based on benthic macroinvertebrates, or any other taxonomic group, are extrapolated to other groups in creating typologies of lotic environments. 相似文献
89.
Genetic analysis of sea-ice bacterial communities of the Western Baltic Sea using an improved double gradient method 总被引:5,自引:0,他引:5
The bacterial diversity of sea ice from Kiel Bight obtained during the rare event of solid ice cover in spring 1996 was analysed by molecular genetic approaches using an improved double gradient denaturing gradient gel electrophoretic method (DG-DGGE) to separate 16S rDNA fragments of approximately 500 bp. The excellent separation of individual bands within these gradient gels allowed us to obtain sequence information and to allocate the phylogenetic position of representative bacteria from the sea ice. The band pattern of the gradient gels revealed a vertical stratification of the bacterial species distribution within the ice and the presence of characteristic bacteria for each layer. According to their 16S rDNA sequences, major bands of the gradient gels represented bacteria closely related to fermenting species of the genera Propionibacterium and Bacteroides and to anoxygenic phototrophic purple sulfur bacteria (Chromatiaceae). Their abundance in horizons of the inner ice core may indicate the existence of oxygen-deficient and anoxic zones or niches and possible primary production by anoxygenic photosynthesis within the investigated Baltic Sea sea ice. This is the first phylogenetic evidence of the presence, and most probably the development, of phototrophic purple sulfur bacteria in sea ice. 相似文献
90.
Localization of a gene for a minor chorion protein in Drosophila melanogaster: a new chorion structural locus 总被引:1,自引:0,他引:1
A minor chorion protein (called s70) with an approximate molecular weight of 70,000 D has been characterized in Drosophila melanogaster. The Staket geographic strain was found to carry an electrophoretic variant of this eggshell component and was used to determine the chromosomal location of the s70 gene. Our results establish a new locus for a chorion gene near yellow on the X chromosome and represent the first mapping of a quantitatively minor eggshell protein. 相似文献