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31.
Sigurdsson S Gudbjarnason S 《Zeitschrift für Naturforschung. C, Journal of biosciences》2007,62(9-10):689-693
The aim of this study was to explore the acetylcholinesterase (AChE) inhibition of several Icelandic medicinal herbs. Ethanolic extracts of Angelica archangelica seeds and the aerial parts of Geranium sylvaticum proved effective, with IC50 values of 2.20 mg/ml and 3.56 mg/ml, respectively. The activity of imperatorin and xanthotoxin from A. archangelica was measured. Xanthotoxin proved much more potent than imperatorin, with an IC50 value of 155 microg/ml (0.72 mM) but that for imperatorin was above 274 microg/ml (1.01 mM). However, furanocoumarins seem to have a minor part in the total activity of this extract. Synergistic interaction was observed between the extracts of A. archangelica and G. sylvaticum. Several medicinal herbs (Achillea millefolium, Filipendula ulmaria, Thymus praecox and Matricaria maritima) did not show AChE inhibitory activity. 相似文献
32.
Rúnarsson OV Malainer C Holappa J Sigurdsson ST Másson M 《Carbohydrate research》2008,343(15):2576-2582
An efficient and chemoselective procedure for preparing highly organosoluble 3,6-di-O-tert-butyldimethylsilyl (TBDMS)-chitosan and chitooligosaccharides is reported. The selective modification of the chitooligosaccharides with 0.50 degree of N-acetylation was achieved by using TBDMSCl as the reagent in combination with DMF/imidazole. These protocols yielded partly TBDMS-substituted chitooligosaccharides that were subsequently reacted with TBDMSOTf in dichloromethane in order to silylate the remaining, more sterically hindered hydroxyl groups. In the case of the chitosan polymer, a mesylate salt of chitosan was silylated using TBDMSCl in DMSO, yielding full silylation of the hydroxyl groups without using N-protection groups. The silyl-protected polymers displayed excellent solubility in a number of common organic solvents. The 3,6-di-O-TBDMS-chitosan and chitooligosaccharides were reacted with acetic anhydride, and deprotected to obtain the corresponding N-acetyl derivatives (chitin and chitinoligosaccharide). Our results show that the readily prepared 3,6-di-O-TBDMS-chitosan and chitooligosaccharides are useful precursors for selective N-modifications in common organic solvents. 相似文献
33.
A kinetic study on the reactions of pivaloyl chloride with a nucleoside H-phosphonate (bisacylphosphite formation), or a protected nucleoside with a free 5'-OH (5'-O-pivaloylation) has been carried out in the presence of differently substituted pyridines. The bisacylphosphite formation is a result of acylation of the mixed carboxylic-phosphonic acid anhydride to give the corresponding bispivaloylphosphite derivative. The rate of this reaction is dependent on the concentration of pyridine derivative and pivaloyl chloride. The 5'-O-pivaloylation reaction is also dependent on the concentration of pyridine derivative and pivaloyl chloride. The rate of both reactions is dependent on the basicity of the pyridine derivative, displaying a higher rate with more basic pyridines. The dependence of log k vs. pKa of pyridine is linear but the slopes are quite different for the two reactions (0.84 for bisacylation and 0.21 for 5'-O-pivaloylation). For both reactions considerably lower rates in the presence of sterically hindered pyridines suggest the existence of nucleophilic catalysis on pivaloyl chloride in reactions with non-hindered pyridines. 相似文献
34.
Egilsson Valgardur Evans Ivor H. Wilkie David 《Molecular genetics and genomics : MGG》1979,177(1):39-46
Molecular Genetics and Genomics - Nineteen haploid yeast (Saccharomyces cerevisiae) strains were used to assess the relative growth inhibitory potencies on fermentable vs. non-fermentable media of... 相似文献
35.
Steinn Gudmundsson Gudny Lilja Oddsdottir Thomas Philip Runarsson Sven Sigurdsson Eythor Kristjansson 《Biomedical signal processing and control》2010,5(4):311-317
A new method is proposed for detecting fraudulent whiplash claims based on measurements of movement control of the neck. The method is noninvasive and inexpensive. The subjects track a slowly moving object on a computer screen with their head. The deviation between the measured and actual trajectory is quantified and used as input to an ensemble of support vector machine classifiers. The ensemble was trained on a group of 34 subjects with chronic whiplash disorder together with a group of 31 healthy subjects instructed to feign whiplash injury. The sensitivity of the proposed method was 86%, the specificity 84% and the area under curve (AUC) was 0.86. This suggests that the method can be of practical use for evaluating the validity of whiplash claims. 相似文献
36.
We selected 125 candidate single nucleotide polymorphisms (SNPs) in genes belonging to the human type 1 interferon (IFN) gene family and the genes coding for proteins in the main type 1 IFN signalling pathway by screening databases and by in silico comparison of DNA sequences. Using quantitative analysis of pooled DNA samples by solid-phase mini-sequencing, we found that only 20% of the candidate SNPs were polymorphic in the Finnish and Swedish populations. To allow more effective validation of candidate SNPs, we developed a four-colour microarray-based mini-sequencing assay for multiplex, quantitative allele frequency determination in pooled DNA samples. We used cyclic mini-sequencing reactions with primers carrying 5′-tag sequences, followed by capture of the products on microarrays by hybridisation to complementary tag oligonucleotides. Standard curves prepared from mixtures of known amounts of SNP alleles demonstrate the applicability of the system to quantitative analysis, and showed that for about half of the tested SNPs the limit of detection for the minority allele was below 5%. The microarray-based genotyping system established here is universally applicable for genotyping and quantification of any SNP, and the validated system for SNPs in type 1 IFN-related genes should find many applications in genetic studies of this important immunoregulatory pathway. 相似文献
37.
Antibiotic resistance is an increasing problem in the health care system and we are in a constant race with evolving bacteria. Biofilm-associated growth is thought to play a key role in bacterial adaptability and antibiotic resistance. We employed a systems biology approach to identify candidate drug targets for biofilm-associated bacteria by imitating specific microenvironments found in microbial communities associated with biofilm formation. A previously reconstructed metabolic model of Pseudomonas aeruginosa (PA) was used to study the effect of gene deletion on bacterial growth in planktonic and biofilm-like environmental conditions. A set of 26 genes essential in both conditions was identified. Moreover, these genes have no homology with any human gene. While none of these genes were essential in only one of the conditions, we found condition-dependent genes, which could be used to slow growth specifically in biofilm-associated PA. Furthermore, we performed a double gene deletion study and obtained 17 combinations consisting of 21 different genes, which were conditionally essential. While most of the difference in double essential gene sets could be explained by different medium composition found in biofilm-like and planktonic conditions, we observed a clear effect of changes in oxygen availability on the growth performance. Eight gene pairs were found to be synthetic lethal in oxygen-limited conditions. These gene sets may serve as novel metabolic drug targets to combat particularly biofilm-associated PA. Taken together, this study demonstrates that metabolic modeling of human pathogens can be used to identify oxygen-sensitive drug targets and thus, that this systems biology approach represents a powerful tool to identify novel candidate antibiotic targets. 相似文献
38.
Rigid spin-labeled nucleoside C, an analog of deoxycytidine that base-pairs with deoxyguanosine, was incorporated into DNA oligomers by chemical synthesis. Thermal denaturation experiments and circular dichroism (CD) measurements showed that C has a negligible effect on DNA duplex stability and conformation. Nucleoside C was incorporated into several positions within single-stranded DNA oligomers that can adopt two hairpin conformations of similar energy, each of which contains a four-base loop. The relative mobility of nucleotides in the alternating C/G hairpin loops, 5'-d(GCGC) and 5'-d(CGCG), was determined by electron paramagnetic resonance (EPR) spectroscopy. The most mobile nucleotide in the loop is the second one from the 5'-end, followed by the third, first and fourth nucleotides, consistent with previous NMR studies of DNA hairpin loops of different sequences. The EPR hairpin data were also corroborated by fluorescence spectroscopy using oligomers containing reduced C (C(f)), which is fluorescent. Furthermore, EPR spectra of duplex DNAs that contained C at the end of the helix showed features that indicated dipolar coupling between two spins. These data are consistent with end-to-end duplex stacking in solution, which was only observed when G was paired to C, but not when C was paired with A, C or T. 相似文献
39.
40.
Elinor K Karlsson Snaevar Sigurdsson Emma Ivansson Rachael Thomas Ingegerd Elvers Jason Wright Cedric Howald Noriko Tonomura Michele Perloski Ross Swofford Tara Biagi Sarah Fryc Nathan Anderson Celine Courtay-Cahen Lisa Youell Sally L Ricketts Sarah Mandlebaum Patricio Rivera Henrik von Euler William C Kisseberth Cheryl A London Eric S Lander Guillermo Couto Kenine Comstock Mike P Starkey Jaime F Modiano Matthew Breen Kerstin Lindblad-Toh 《Genome biology》2013,14(12):1-16