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81.
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83.
Single-stranded DNA binding proteins (SSBs) are vital in all organisms. SSBs of Escherichia coli (EcoSSB) and Mycobacterium tuberculosis (MtuSSB) are homotetrameric. The N-terminal domains (NTD) of these SSBs (responsible for their tetramerization and DNA binding) are structurally well defined. However, their C-terminal domains (CTD) possess undefined structures. EcoSSB NTD consists of β1-β1′-β2-β3-α-β4-β451-β452-β5 secondary structure elements. MtuSSB NTD includes an additional β-strand (β6) forming a novel hook-like structure. Recently, we observed that MtuSSB complemented an E. coli Δssb strain. However, a chimeric SSB (mβ4-β5), wherein only the terminal part of NTD (β4-β5 region possessing L45 loop) of EcoSSB was substituted with that from MtuSSB, failed to function in E. coli in spite of its normal DNA binding and oligomerization properties. Here, we designed new chimeras by transplanting selected regions of MtuSSB into EcoSSB to understand the functional significance of the various secondary structure elements within SSB. All chimeric SSBs formed homotetramers and showed normal DNA binding. The mβ4-β6 construct obtained by substitution of the region downstream of β5 in mβ4-β5 SSB with the corresponding region (β6) of MtuSSB complemented the E. coli strain indicating a functional interaction between the L45 loop and the β6 strand of MtuSSB. 相似文献
84.
Ming Kai Tan Crystal Yun Han Yong Sigfrid Ingrisch Hanyrol H. Ahmad Sah Rodzay bin Haji Abdul Wahab Philip Michael Johns 《分类学与生物多样性》2013,11(8):731-742
An important function of song production by male crickets is to attract conspecific females. These sound signals can be used to infer species boundaries as they can provide indirect evidence for reproductive isolation. However, many studies of orthopteran diversity in South-east Asia are based mainly on morphology and only occasionally acoustics. As such, there is a lack of information on how acoustic data can be congruent with morphological data when used to delineate species. Crickets of the genus Gymnogryllus (Grylloidea, Gryllidae), are such an example. Gymnogryllus are relatively speciose, but their calling songs have not been studied. We collected specimens and calling songs of five Gymnogryllus species from South-east Asia. The acoustic parameters of the calls, along with male tegminal venation and morphology genitalia, were compared. All data types showed congruency in distinguishing G. sylvestris and G. leucostictus from each other and from the other species. Inferring species boundaries for G. angustus, G. malayanus, and G. unexpectus using acoustics and tegminal morphometry proves to be more challenging. While acoustics, tegminal morphometry, and genital morphology are likely to be useful for inferring species of Gymnogryllus from different species groups, greater coverage of taxa is needed to resolve taxonomy of closely related Gymnogryllus. 相似文献
85.
Irene Llorente‐Folch Ignasi Sahún Laura Contreras María José Casarejos Josep María Grau Takeyori Saheki María Angeles Mena Jorgina Satrústegui Mara Dierssen Beatriz Pardo 《Journal of neurochemistry》2013,124(3):347-362
The mitochondrial transporter of aspartate‐glutamate Aralar/AGC1 is a regulatory component of the malate‐aspartate shuttle. Aralar deficiency in mouse and human causes a shutdown of brain shuttle activity and global cerebral hypomyelination. A lack of neurofilament‐labeled processes is detected in the cerebral cortex, but whether different types of neurons are differentially affected by Aralar deficiency is still unknown. We have now found that Aralar‐knockout (Aralar‐KO) post‐natal mice show hyperactivity, anxiety‐like behavior, and hyperreactivity with a decrease of dopamine (DA) in terminal‐rich regions. The striatum is the brain region most affected in terms of size, amino acid and monoamine content. We find a decline in vesicular monoamine transporter‐2 (VMAT2) levels associated with increased DA metabolism through MAO activity (DOPAC/DA ratio) in Aralar‐KO striatum. However, no decrease in DA or in the number of nigral tyrosine hydroxylase‐positive cells was detected in Aralar‐KO brainstem. Adult Aralar‐hemizygous mice presented also increased DOPAC/DA ratio in striatum and enhanced sensitivity to amphetamine. Our results suggest that Aralar deficiency causes a fall in GSH/GSSG ratio and VMAT2 in striatum that might be related to a failure to produce mitochondrial NADH and to an increase of reactive oxygen species (ROS) in the cytosol. The results indicate that the nigrostriatal dopaminergic system is a target of Aralar deficiency. 相似文献
86.
S. P. Sah C. L. Bryant J. Leppälammi-Kujansuu K. Lõhmus I. Ostonen H.-S. Helmisaari 《Plant and Soil》2013,363(1-2):77-86
Background and aims
The main objectives of this study were to determine how the carbon age of fine root cellulose varies between stands, tree species, root diameter and soil depth. In addition, we also compared the carbon age of fine roots from soil cores of this study with reported values from the roots of the same diameter classes of ingrowth cores on the same sites.Methods
We used natural abundance of 14C to estimate root carbon age in four boreal Norway spruce and Scots pine stands in Finland and Estonia.Results
Age of fine root carbon was older in 1.5–2 mm diameter fine roots than in fine roots with <0.5 mm diameter, and tended to be older in mineral soil than in organic soil. Fine root carbon was older in the less fertile Finnish spruce stands (11–12 years) than in the more fertile Estonian stand (3 and 8 years), implying that roots may live longer in less fertile soil. We further observed that on one of our sites carbon in live fine roots with the 1.5–2 mm diameter was of similar C age (7–12 years) than in the ingrowth core roots despite the reported root age in the ingrowth cores – being not older than 2 years.Conclusions
From this result, we conclude that new live roots may in some cases use old carbon reserves for their cellulose formation. Future research should be oriented towards improving our understanding of possible internal redistribution and uptake of C in trees. 相似文献87.
Harish Rajak Bhupendra Singh Thakur Avineesh Singh Kamlesh Raghuvanshi Anil Kumar Sah Ravichandran Veerasamy Prabodh Chander Sharma Rajesh Singh Pawar Murli Dhar Kharya 《Bioorganic & medicinal chemistry letters》2013,23(3):864-868
Two novel series of N4-(5-(2/3/4-substituted-phenyl)-1,3,4-oxadiazol-2-yl)-N1-(2-methyl-5-(prop-1-en-2-yl)cyclohex-2-enylidene)semicarbazide and N4-(5-(2/3/4-substituted-phenyl)-1,3,4-oxadiazol-2-yl)-N1-(3,7-dimethylocta-3,6-dienylidene)-semicarbazide were synthesized to meet structural prerequisite indispensable for anticonvulsant activity. The anticonvulsant activities of the compounds were investigated using maximal electroshock seizure (MES), subcutaneous pentylenetrtrazole (scPTZ) and subcutaneous strychnine (scSTY) models. The rotorod test was conducted to evaluate neurotoxicity. Some of the selected active compounds were subjected to GABA assay to confirm their mode of action. The outcome of the present investigations proved that the four binding sites pharmacophore model is vital for anticonvulsant activity. The efforts were also made to establish structure–activity relationships among test compounds. 相似文献
88.
To test the reliability of the radiocarbon method for determining root age, we analyzed fine roots (originating from the years 1985?C1993) from ingrowth cores with known maximum root age (1?C6?years old). For this purpose, three Scots pine (Pinus sylvestris L.) stands were selected from boreal forests in Finland. We analyzed root 14C age by the radiocarbon method and compared it with the above-mentioned known maximum fine root age. In general, ages determined by the two methods (root 14C age and ingrowth core root maximum age) were in agreement with each other for roots of small diameter (<0.5?mm). By contrast, in most of the samples of fine roots of larger diameter (1.5?C2?mm), the 14C age of root samples of 1987?C1989 exceeded the ingrowth core root maximum age by 1?C10?years. This shows that these roots had received a large amount of older stored carbon from unknown sources in addition to atmospheric CO2 directly from photosynthesis. We conclude that the 14C signature of fine roots, especially those of larger diameter, may not always be indicative of root age, and that further studies are needed concerning the extent of possible root uptake of older carbon and its residence time in roots. 相似文献
89.
The ability of Aspergillus fumigatus
l-amino acid oxidase (l-aao) to cause the resolution of racemic mixtures of dl-amino acids was investigated with dl-alanine, dl-phenylalanine, dl-tyrosine, and dl-aspartic acid. A chiral column, Crownpak CR+ was used for the analysis of the amino acids. The enzyme was able to cause the
resolution of the three dl-amino acids resulting in the production of optically pure d-alanine (100% resolution), d-phenylalanine (80.2%), and d-tyrosine (84.1%), respectively. The optically pure d-amino acids have many uses and thus can be exploited industrially. This is the first report of the use of A. fumigatus
l-amino acid oxidase for racemic resolution of dl-amino acids. 相似文献
90.
1-Naphthol 2-hydroxylase (1-NH) which catalyzes the conversion of 1-naphthol to 1,2-dihydroxynaphthalene was purified to homogeneity
from carbaryl-degrading Pseudomonas sp. strain C6. The enzyme was found to be a homodimer with subunit molecular weight of 66 kDa. UV, visible and fluorescence
spectral properties, identification of flavin moiety by HPLC as FAD, and reconstitution of apoenzyme by FAD suggest that enzyme
is FAD-dependent. 1-NH accepts electron from NADH as well as NADPH. Besides 1-naphthol (K
m, 9.1 μM), the enzyme also accepts 5-amino 1-naphthol (K
m, 6.4 μM) and 4-chloro 1-naphthol (K
m, 2.3 μM) as substrates. Enzyme showed substrate inhibition phenomenon at high concentration of 1-naphthol (K
i, 283 μM). Stoichiometric consumption of oxygen and NADH, and biochemical properties suggest that 1-NH belongs to FAD containing
external flavomonooxygenase group of oxido-reductase class of enzymes. Based on biochemical and kinetic properties, 1-NH from
Pseudomonas sp. strain C6 appears to be different than that reported earlier from Pseudomonas sp. strain C4. Chemical modification and protection by 1-naphthol and NADH suggest that His, Arg, Cys, Tyr and Trp are at
or near the active site of 1-NH. 相似文献