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1.
Summary The NMR shift reagent, Europium(III)-tris-(1,1,1,2,2,3,3)-heptafluoro-7,7-dimethyl-4-6-octanedione [Eu(fod)3], complexes efficiently with-amino acid esters in chloroform. These complexes exhibit characteristic circular dichroism (CD) spectral patterns in the 350-250 nm region. A fast and simple procedure (also in microscale) has been worked out which utilizes the signs of these CD bands for the determination of the absolute configuration at the-carbon atomin situ. In the L-series, a positive CD band is observed at around 310 nm and a negative one in the 290-280 nm region. The CD spectra of the Eu complexes of the D-isomers are mirror images of those of the L-configurations. An empirical rule is proposed.Presented in part at the 2nd International Congress on Amino Acids and Analogues, Vienna, Austria, August 5–9, 1991. 相似文献
2.
Leaf rust induced volatile organic compounds signalling in willow during the infection 总被引:1,自引:0,他引:1
Merje Toome Pille Randjärv Lucian Copolovici Ülo Niinemets Katrin Heinsoo Anne Luik Steffen M. Noe 《Planta》2010,232(1):235-243
Plants are known to emit volatile organic compounds (VOC) in response to various biotic or abiotic stresses. Although the
VOC emission in the case of insect attacks is well described, there is only little known about the impact of pathogens on
plant emission. In the present study, we used a willow-leaf rust system to describe the effects of a biotrophic fungal infection
on the VOC emission pattern of willow leaves. We detected that isoprene emissions from rust-infected leaves decreased threefold
compared to control. The total monoterpene emissions did not change although a stress-signalling compound (Z)-β-ocimene showed an increase in infected plants on several days. The infection also increased the emission of sesquiterpenes
and lipoxygenase products (LOX) by factors of 175-fold and 10-fold, respectively. The volatile emission signals showed two
clear peaks during the experiment. At 6, 7 and 12 days post-infection (dpi), the relative volatile emission signal increased
to about sixfold compared to uninfected plants. These time points are directly connected to rust infection since at 6 dpi
the first rust pustules appeared on the leaves and at 12 dpi necrosis had developed around several pustules. We present correlations
between LOX and sesquiterpene emission signals, which suggest at least two different steps in eliciting the volatile emission. 相似文献
3.
Silvano De Bernardo Manfred Weigele Voldemar Toome Karin Manhart Willy Leimgruber Peter Böhlen Stanley Stein Sidney Udenfriend 《Archives of biochemistry and biophysics》1974,163(1):390-399
Fluorescamine is a useful reagent for the fluorometric assay of primary amines. The extent of the reaction between fluorescamine and primary amines, as well as the fluorescence intensities of the resulting fluorophors depend on pH, solvent composition and reagent concentration. Optimum values for these variables further depend on the amine under study. The influence of these parameters on the fluorogenic reaction of representative amines, and on their fluorophoric derivatives has been investigated, and the results are reported here. 相似文献
4.
It is often suggested that weeds from the same family as the crop plant may increase insect pest damages by providing shelter and additional oviposition opportunities. We compared the relative attractiveness of Brassica rapa L., B. juncea L., Sinapis alba L. and B. napus L. (Capparales: Brassicaceae) to the pollen beetle and its hymenopteran parasitoids in field conditions. Our results revealed that none of the investigated plants increased the pest abundance on B. napus plants. On the contrary, B. juncea and S. alba lured beetles away from B. napus during its damage-susceptible stage. The parasitism rate of pollen beetle larvae was the highest on B. juncea plants, indicating that cruciferous weeds could improve the natural control of the pollen beetle by providing additional hosts for parasitoids. Therefore, close relatives of oilseed rape might be used to trap pollen beetle adults, but also to support populations of natural enemies that could decrease the number of beetles. 相似文献
5.
B Dayal G Salen J Padia S Shefer G S Tint T H Williams V Toome G Sasso 《Chemistry and physics of lipids》1992,61(3):271-281
Described herein are the stereoselective syntheses of the (24R, 24S) and (25R, 25S) isomers of 5 beta-cholestane-3 alpha,7 alpha,12 alpha,24,25-pentols and 5 beta-cholestane-3 alpha,7 alpha,12 alpha,25,26-pentols by using a modified osmium-catalyzed Sharpless asymmetric dihydroxylation process. Also presented herein are the results of lanthanide-induced CD Cotton effect measurements and 1H- and 13C-nuclear magnetic resonance studies of (24R, 24S) and (25R, 25S)-5 beta-cholestanepentols and their derivatives. These compounds were required to study the biosynthesis of cholic acid from cholesterol. 相似文献
6.
The influence of column configuration on the separation of hen egg-white proteins using Whatman DE52 and QA52 anion-exchange cellulose has been investigated. Using a 100 ml volume axial flow column (6.6 cm x 4.4 cm i.d.) we achieved flow rates of up to 25 ml/min i.e. 15 bed volumes/h after which higher flow was restricted due to pressure constraints within the system. Under radial flow conditions using a 100 ml column flow rates of up to 150 ml/min i.e. 90 bed volumes/h were achieved using DE52 and QA52. While chromatographic resolution was superior under axial flow at the lower flow rates excellent resolution was maintained at up to 150 ml/min using the radial flow column. This is a consequence of the fast kinetics of adsorption/desorption exhibited by DE52 and QA52. The data indicate that it is the column configuration and not the cellulose matrix which influences flow performance. 相似文献
7.
A M Felix E P Heimer C T Wang T J Lambros A Fournier T F Mowles S Maines R M Campbell B B Wegrzynski V Toome 《International journal of peptide and protein research》1988,32(6):441-454
A novel cyclic GRF analog, cyclo(Asp8-Lys12)-[Asp8,Ala15]-GRF(1-29)-NH2, i.e. cyclo8,12[Asp8,Ala15]-GRF(1-29)-NH2, was synthesized by the solid phase procedure and found to retain significant biological activity. Solid phase cyclization of Asp8 to Lys12 proceeded rapidly (approximately 2 h) using the BOP reagent. Substitution of Ala2 with D-Ala2 and/or NH2-terminal replacement (desNH2-Tyr1 or N-MeTyr1) in the cyclo8,12[Asp8,Ala15]-GRF(1-29)-NH2 system resulted in highly potent analogs that were also active in vivo. Conformational analysis (circular dichroism and molecular dynamics calculations based on NOE-derived distance constraints) demonstrated that cyclo8,12[Asp8,Ala15]-GRF(1-29)-NH2 contains a long alpha-helical segment even in aqueous solution. A series of cyclo8,12 stereoisomers containing D-Asp8 and/or D-Lys12 were prepared and also found to be highly potent and to retain significant alpha-helical conformation. The high biological activity of cyclo8,12[N-MeTyr1,D-Ala2,Asp8,Ala15]-GRF(1-29)- NH2 may be explained on the basis of retention of a preferred bioactive conformation. 相似文献
8.
Lauris Kaplinski Ott Scheler Sven Parkel Priit Palta Kadri Toome Ants Kurg Maido Remm 《BMC biotechnology》2010,10(1):34
Background
The hybridization of synthetic Streptococcus pneumoniae tmRNA on a detection microarray is slow at 34°C resulting in low signal intensities. 相似文献9.
The absolute configurations of the C27 pentahydroxy bile alcohols present in bile and feces of two patients with cerebrotendinous xanthomatosis (CTX) were determined by circular dichroism (CD) spectroscopy. The CD spectra of 5beta-cholestane-3alpha,7alpha,12alpha,24alpha,25-pentol in the presence of Eu(fod)3 [tris(1,1,1,2,2,3,3-heptafluoro-7,7-dimethyloctane-4,6-dionato) europium (III)] exhibited a negative Cotton effect and was assigned to 24R absolute configuration. Conversely, 5beta-cholestane-3alpha,7alpha,12alpha,24beta,25-pentol showed a strong positive Cotton effect and was assigned the 24S configuration. These assignments were based upon comparison with a model compound, 5-cholestene-3beta,24(R),25-triol, whose single-crystal X-ray structure has been determined. The importance of these data is to establish a structural mechanism for the conversion of 5beta-cholestane-3alpha,7alpha,12alpha,24S,25-pentol rather than 5beta-cholestane-3alpha,7alpha,12alpha,24R,25-pentol into cholic acid in man as well as in animals. 相似文献
10.
V. Toome B. Wegrzynski J. Dell 《Biochemical and biophysical research communications》1977,74(2):825-830
The free amino group of a dipeptide reacts efficiently with fluores-camine (FLURAM®) to form pyrrolinone-type chromophores with long wavelength absorption maxima in the 380 nm region. A simple test tube procedure is described which allows determination of the absolute configuration of the NH2-terminal amino acids of the dipeptides based on the chiroptical properties of their chromophoric derivatives. 相似文献