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151.
152.
Elżbieta Winnicka Jolanta Szymańska Marianna Kańska 《Isotopes in environmental and health studies》2016,52(3):231-238
The isotopomers of halogen derivatives of l-tryptophan (l-Trp) (4′-F-, 7′-F-, 5′-Cl- and 7′-Br-l-Trp), specifically labelled with deuterium in α-position of the side chain, were obtained by enzymatic coupling of the corresponding halogenated derivatives of indole with S-methyl-l-cysteine in 2H2O, catalysed by enzyme tryptophanase (EC 4.1.99.1). The positional deuterium enrichment of the resulting tryptophan derivatives was controlled using 1H NMR. In accordance with the mechanism of the lyase reaction, a 100% deuterium labelling was observed in the α-position; the chemical yields were between 23 and 51%. Furthermore, β-F-l-alanine, synthesized from β-F-pyruvic acid by the l-alanine dehydrogenase reaction, has been tested as a coupling agent to obtain the halogenated deuterium-labelled derivatives of l-Trp. The chemical yield (~30%) corresponded to that as observed with S-methyl-l-cysteine but the deuterium label was only 63%, probably due to the use of a not completely deuterated incubation medium. 相似文献
153.
Ferdani R Li R Pajewski R Pajewska J Winter RK Gokel GW 《Organic & biomolecular chemistry》2007,5(15):2423-2432
Seven synthetic anion transporters (SAT) of the general form R(2)N-COCH(2)OCH(2)CO-(Gly)(3)-Pro-(Gly)(3)-OR' were prepared. Three pairs of compounds each contained twin n-hexyl, n-decyl, and n-octadecyl (R) groups at the N-terminus and one contained twin n-tetradecyl groups. Three of the compounds were C-terminated by benzyl and three by heptyl (R') residues. The ability of these compounds to mediate ion release from phospholipid vesicles was assessed. Chloride release was measured by ion selective electrode measurements and by chloride quenching of the fluorescent dye lucigenin. Transport of the anion carboxyfluorescein (CF) was measured by fluorescence dequenching. Differences in both the C- (R') and N-terminal (R) residues within the ionophores affected anion transport. The chloride release data acquired by ion selective electrode and fluorescence methods were similar but not identical. A possible carrier mechanism for Cl(-) transport was discredited. Both Cl(-) and CF anions were released from vesicles by these compounds. The results of CF and Cl(-) transport showed good consistency when the ionophore's N-terminal chains were either decyl or octadecyl but not when they were hexyl. The transport of CF and Cl(-) appears to be fundamentally different when R is C(6) compared to C(10) or C(18). Differences between the behavior of SATs with Cl(-) and CF were also reflected in negative ion mass spectrometric studies. 相似文献
154.
Jokiel M Shcharbin D Janiszewska J Urbanczyk-Lipkowska Z Bryszewska M 《Journal of fluorescence》2007,17(1):73-79
The interactions between polycationic poly-lysine dendrimers and hydrophobic fluorescent probes (anionic ANS and neutral Prodan)
were studied. R121 and R131 dendrimers were not able to interact with anionic and neutral hydrophobic groups. R124 was able
to interact with neutral and anionic hydrophobic fluorescent probes, however mainly through hydrophobic forces. Dendrimers
R155 and R169 showed the maximal effects. The strongest interactions observed for R169 can be explained by intramolecular
folding (stacking) of its two L-proline residues. Using double fluorescence titration technique for ANS probe allowed to receive
such constant of binding and the number of binding centers: for R121, 1.8·103 (mol/l)−1 and 1.07; for R124, 12.1·103 (mol/l)−1 and 0.48; for R131, 4.7·103 (mol/l)−1 and 0.48; for R155, 9.2·103 (mol/l)−1 and 1.36; for R169, 39.6·103 (mol/l)−1 and 0.97. Thus, neutral and anionic hydrophobic probes can be used for the fast preliminary screening of binding properties
of newly synthesized polycationic dendrimers. 相似文献
155.
156.
Jolanta WierzejskaManami Ohshima Toshiyasu InuzukaTetsuya Sengoku Masaki TakahashiHidemi Yoda 《Tetrahedron letters》2011,52(11):1173-1175
The first total synthesis of (+)-batzellaside B and its C8-epimer was completed from a known l-arabinose-derived tribenzyl ether in 22 steps with overall yields of 3.9% and 5.4%, respectively. The absolute configuration of (+)-batzellaside B was unambiguously determined to be 1S,3S,4S,5R,8S by the Mosher analysis of a synthetic intermediate prepared through a separate route. 相似文献
157.
A three-step one pot reaction/purification protocol was developed to facilitate rapid access to benzimidazole-based nucleosides, for which benzoylated benzimidazoribosyl nucleosides incorporating boronic esters were key reaction intermediates. 相似文献
158.
Mazoniene E Joceviciute S Kazlauske J Niemeyer B Liesiene J 《Colloids and surfaces. B, Biointerfaces》2011,83(1):160-164
Mucoadhesivity of water-soluble polymers is an important factor, when testing their suitability for controlled drug delivery systems. For this purpose, the interaction of new cationic cellulose polyelectrolytes with lyophilized mucin was investigated by means of turbidimetric titration, microscopy and measurement of zeta potential and particle size changes in the system. Results show that the cellulose derivatives interact with mucin. This interaction became stronger if cellulose macromolecules contained positively charged groups and an electrostatic interaction with the negatively charged mucin particles occurred. Under certain conditions flocculation of mucin particles by the cellulose polyelectrolyte was observed. 相似文献
159.
Ewa Dro?d?-Cie?la Jan Wyrwa Jolanta Bro? Mieczys?aw R?kas 《Journal of Thermal Analysis and Calorimetry》2012,108(3):1051-1057
Ceramic?Cmetal composites (cermets) containing 4?mol% yttria-zirconia (4YSZ) and Ni particles as anode materials in solid oxide fuel cells were prepared by two methods. The first method involves nickel oxalate dihydrate precipitation on the 4YSZ powder and decomposition at 360?°C in inert Ar atmosphere. The second method consists of impregnation of the 4YSZ pellets with an aqueous solution of nickel nitrate. The temperature of oxalate decomposition was determined on the basis of TG/DTA experiments. Gaseous products of decomposition were analyzed by mass spectrometry. The structure of the materials was characterized by X-ray diffraction, scanning electron microscopy, porosity studies, and particle size measurements. The thermal expansion coefficient (TEC) was determined by dilathometric method. Electrochemical impedance spectroscopy was used to determine the electrical conductivity. Thus, determined TECs, porosity, and electrical properties were found suitable for anode materials of fuel cells. 相似文献
160.
The possible role of iron in neurodegeneration was studied by various techniques: electron microscopy, enzyme-linked immunosorbent assay, M?ssbauer spectroscopy, atomic absorption, ultrasonography and magnetic resonance imaging. The measurements were made on human tissues extracted from liver and from brain structures involved in diseases of the human brain: substantia nigra (Parkinson's, PD), hippocampal cortex (Alzheimer's, AD) and globus pallidus (progressive supranuclear palsy, PSP). The sizes of the iron cores of ferritin, the main iron storage compound in tissues, were found to be smaller in brain than in liver. Brain ferritin has a higher proportion of H to L chains compared to liver. A significant decrease of the concentration of L chains in PD compared to control was found. No increase in the concentration of iron in PD versus control was detected; however, there was an increase of labile iron, which constitutes only 2‰ of brain iron. In AD an increase in the concentration of ferritin was noticed, without a significant increase in iron concentration. In PSP an increase of total iron was observed. Our findings suggest that the mechanisms leading to the death of nerve cells in these three diseases may be different, although all may be related to iron mediated oxidative stress. 相似文献