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991.
Pyrenebutanoate, a fluorescent amphiphilic probe, is suggested here as a capillary zone electrophoresis (CZE) buffer additive for dynamic modification and analysis of microbial cells. Mixed cultures of microorganisms Escherichia coli, Candida albicans, Enterococcus faecalis and Staphylococcus epidermidis were concentrated, resolved by CZE and detected. Using UV excitation for on-column fluorometric detection, a detection sensitivity for the microorganisms on the order of from one to tens of injected cells was achieved. 相似文献
992.
Karel Blha 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》1973,85(15):678-678
993.
A way of controlling the maximum allowable oven temperature during on-column injection by the column pressure drop is suggested. An arrangement using a restriction at the column outlet for adjustment of the column inlet pressure while maintaining the same column flow has been studied. Compared to non-restricted flow, substantially increased maximum oven temperatures were obtained during on-column injection. Injections at elevated temperatures resulted in an increased speed of analysis and decreased solute adsorption on the surface of the contaminated retention gap. The method is generally applicable to analysis of high boiling mixtures. In particular, with GC-AED, such an arrangement yields a higher sensitivity due to an increased solute interaction with the excitation plasma. 相似文献
994.
Bruno Kamber Albert Hartmann Karel Eisler Bernhard Riniker Hans Rink Peter Sieber Werner Rittel 《Helvetica chimica acta》1980,63(4):899-915
Previously reported studies of the iodine oxidation of S-trityl-cysteine peptides and S-acetamidomethyl-cysteine peptides, leading directly to cystine peptides, have been extended. Detailed investigations have been made of the reactivities of the S-trityl and the S-acetamidomethyl group towards iodine in various solvents. In chloroform, methylene chloride, trifluoroethanol, and hexafluoroisopropyl alcohol the differences in the reaction rates of the two groups have been found to be extremely large, allowing the selective conversion of the tritylthio groups to disulfides in the presence of the S-acetamidomethyl derivatives. In a second group of solvents, consisting of methanol, acetic acid, dioxane, and mixtures of these solvents with water, simultaneous iodine oxidation of S-trityl- and S-acetamidomethyl-cysteine peptides leads to a preferential combination of these two residues, resulting in predominantly asymmetrical cystine derivatives. - The suitability of the two sulfur-protecting groups in the synthesis of cyclic cystine peptides has been assessed. - Possible reaction mechanisms are discussed. - The scope and limitations of iodine oxidation in peptide synthesis have been studied. The applicability of the method has been demonstrated in the preparation of the open-chain asymmetrical cystine peptide 5 , the protected somatostatin derivative 17 , and the A(1–13) segment 19 of human insulin, previously employed in the total synthesis of this hormone. 相似文献
995.
Novák P Man P Tucková L Tlaskalová-Hogenová H Bezouska K Havlícek V 《Journal of mass spectrometry : JMS》2002,37(5):507-511
Celiac disease, a chronic disorder of the small intestine, is caused by dietary gluten and is characterized by villous atrophy and local inflammation associated with infiltration of B and T lymphocytes and/or macrophages into the intestinal wall. In genetically predisposed individuals, the infiltrating cells are activated by gluten, gliadin and their proteolytic fragments and produce chemokines, cytokines and reactive radicals. The sequence of one of the macrophage-stimulatory gliadin peptic fragment was determined by mass spectrometry (MS) as VSFQQPQQQYPSSQ. The role of tissue transglutaminase (tTG) in innate immunity stimulation was studied by mass spectrometric monitoring of sequence changes in this active peptide. Two sites of glutamine deamidation in this peptide were localized by high-resolution scanning in MS/MS mode in an ion trap. A single deamidation in the parent peptide led to the complete loss of its stimulatory effect on macrophages. 相似文献
996.
Synytsya A Král V Blechová M Volka K 《Journal of photochemistry and photobiology. B, Biology》2004,74(2-3):73-84
Biolocalisation and photochemical properties of novel macrocyclic photosensitisers, guanidiniocarbonyl-substituted tetraphenylporphyrin (1) and sugar-substituted sapphyrin (2) were investigated by spectroscopic methods. Both photosensitisers absorb in far visible region and showed good tumour localisation. Photosensitiser 2 demonstrated significantly larger absolute and relative to normal tissue (T/N) amount in tumour (330 microg g(-1) wet tissue, T/N=19.0) than photosensitiser 1 did (13 microg g(-1) wet tissue, T/N=2.1). According to iodometric and uric acid assays, compound 1 produced large amount of 1O2 (phidelta=0.60-0.68), while compound 2 showed non-significant 1O2 production (phidelta=0.04). The electronic spectroscopic study confirms that only photosensitiser 1 is able to mediate photooxidation of model compounds (BSA, poly(Trp), Tyr, Trp, and GMP) after light irradiation. Pour photochemical activity of compound 2 was explained by its self-aggregation. Raman spectroscopic study indicated that monomerised photosensitiser 2 effectively damaged BSA and calf thymus DNA after light excitation at the conditions of high excess of these macromolecules. 相似文献
997.
Purines and pyrimidines are of interest owing to their significance in processes in living organisms. Mass spectrometry is a promising analytical tool utilized in their analysis. Two atmospheric pressure ionization (API) methods (electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI)) in both negative and positive modes applied to selected purine and pyrimidine metabolites (markers of inherited metabolic disorders) were studied. APCI is less sensitive to alkali metal cations present in a sample and offers higher response than ESI for studied compounds. Both of the techniques afford quasi-molecular ions, but fragmentation also occurs to a certain extent. However, the application of collision-induced dissociation of quasi-molecular ions is essential to confirm a certain metabolite in a sample. Fragmentation of both positive and negative ions was evaluated using multi-stage mass spectrometric experiments. Typical neutral losses correspond to molecules NH(3), H(2)O, HCN, CO, H(2)NCN, HNCO and CO(2). The ion [NCO](-) arises in the negative mode. The cleavage of the glycosidic C-N bond is characteristic for relevant metabolites. Other neutral losses (CH(2)O, C(2)H(4)O(2) and C(3)H(6)O(3)) originate from fragmentation of the glycosidic part of the molecules. In addition to fragmentation, the formation of adducts of some ions with applied solvents (H(2)O, CH(3)OH) was observed. The composition of the solution infused into the ion source affects the appearance of the mass spectra. Tandem mass spectra allow one to distinguish compounds with the same molecular mass (uridine-pseudouridine and adenosine-2'-deoxyguanosine). Flow injection analysis APCI-MS/MS was tested on model samples of human urines corresponding to adenosine deaminase deficiency and xanthine oxidase deficiency. In both cases, the results showed potential diagnostic usefulness. 相似文献
998.
Karel Dostál Antonín Růžička Marta Sochorcová 《Monatshefte für Chemie / Chemical Monthly》1970,101(1):208-215
Zusammenfassung Im Unterschied zu AgSO3NH2, das sich in flüssigem NH3 glatt auflöst und quantitativ in den Aminkomplex [Ag(NH3)2] SO3NH2 übergeht, reagiert AgSeO3NH2 stark exotherm, wobei neben [Ag(NH3)2]SeO3NH2, NH4SeO3NH2 und sehr kleinen Mengen einer bisher nicht identifizierten Substanz durch Kondensation, die etwa zu 60% verläuft, auch das Trisilbersalz der Imidodiselensäure als Aminkomplex [Ag(NH3)2]3[O3Se–N–SeO3] entsteht.Nach einem einfachen Reinigungsverfahren wurde aus diesem Komplex Ag3[O3Se–N–SeO3] erhalten und daraus die Imidodiselenate Na3[O3Se–N–SeO3] · 3 H2O, K3[O3Se–N–SeO3] · H2O, (NH4)3[O3Se–N–SeO3] und Ba3[O3Se–N–SeO3]2 · 5H2O als kristalline Substanzen dargestellt, die näher charakterisiert und thermogravimetrisch und differentialthermoanalytisch untersucht wurden.
Mit 3 Abbildungen
K. Dostál undA. Rika, Z. Chem.8, 153 (1968). (Vorläufige kurze Mitteilung). 相似文献
Reaction of silver amidoselenate with ammonia and preparation of imidodiselenates
Contrary to AgSO3NH2, which dissolves in liquid NH3 with quantitat. conversion to [Ag(NH3)2]SO3NH2, AgSeO3NH2 in a strongly exothermic reaction yields several products: [Ag(NH3)2]SeO3NH2, NH4SeO3NH2, small amounts of an as yet unidentified compound, and in a condensation reaction to about 60% the amine complex of the trisilver salt of imido-diselenic acid.A simple purification gives Ag3[O3Se–N–SeO3], and from this the crystalline imido-diselenates Na3[O3Se–N–SeO3] · 3 H2O, K3[O3Se–N–SeO3] · H2O, (NH4)3[O3Se–N–SeO3] and Ba3[O3Se–N–SeO3]2 · 5 H2O where prepared and characterized thermogravimetrically, and by the method of differential thermoanalysis.
Mit 3 Abbildungen
K. Dostál undA. Rika, Z. Chem.8, 153 (1968). (Vorläufige kurze Mitteilung). 相似文献
999.
A fluorescence detection system for capillary liquid separation methods is described. The system is based on a silica capillary coated with a low refractive index fluoropolymer Teflon AF that serves both as a separation channel and as a liquid core waveguide (LCW). A fibre-coupled laser excites separated analytes in a detection point and arising fluorescence is collected at one end of the LCW capillary into the other optical fibre which brings it to a compact charge-coupled device (CCD) array spectrometer installed in a desktop computer. No additional components such as focusing optics or filters are necessary. This system was used for detecting isoelectrically focused fluorescent low-molecular-mass pI (isoelectric point) markers and fluorescein isothiocyanate (FITC) labelled proteins. The ability of the system to acquire fluorescent spectra is also demonstrated. 相似文献
1000.
Michal Pechar Karel Ulbrich Markta Jelínkov Blanka íhov 《Macromolecular bioscience》2003,3(7):364-372
The synthesis and physico‐chemical characterisation of biodegradable multiblock polymer drug carriers based on poly(ethylene glycol) (PEG) are described. The blocks of PEG ( = 2 000) are interconnected by an enzymatically degradable tripeptide derivative consisting of one Lys and two Glu residues. An anticancer drug, doxorubicin (Dox), was attached to the polymer carrier by a Gly‐Phe‐Leu‐Gly tetrapeptide spacer, which is also susceptible to degradation by lysosomal enzymes. A targeting polyclonal antibody was covalently linked to the polymer‐Dox conjugate by the aminolytic reaction of reactive sulfosuccinimidyl ester groups of the polymer with the protein. The resulting antibody‐polymer‐drug conjugates were characterised by SEC, UV/VIS spectrophotometry and amino acid analysis. Although the studied polymers show only a moderate antiproliferative activity against concanavalin A‐stimulated murine splenocytes and a murine T‐cell EL 4 lymphoma in vitro, they exhibited significant antitumour efficiency against murine T‐cell EL 4 lymphoma in vivo.