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51.
The effect of ethanol on human serum albumin stability in aqueous solution
was studied by use of differential scanning calorimetry. A deconvolution of
DSC traces in 2-state model with ΔC
p=0
and ΔC
p≠0
was performed and analysed to obtain information on the interaction of ethanol
with different parts of albumin molecule both fatty acid containing and fatty
acid free. The differences in ethanol binding affinity for both kinds of albumin
were found. At very low concentrations ethanol was observed to be a stabilizer
of the folded state of albumin contrary to the higher concentration where
its binding to the unfolded protein predominates. 相似文献
52.
Alan R. Katritzky Clifford H. Watson Zofia Dega-Szafran John R. Eyler 《Journal of mass spectrometry : JMS》1989,24(11):1017-1021
Three novel collisionally induced dissociation pathways, additional to the usual formation of pyridine or pyridinium cation, are described for laser-desorbed N-substituted pyridinium cations. Particularly prevalent is the formation of an ion of m/z 94, corresponding to [PyCH3]+. Doubly charged pyridiniums tend to lose H+, and one example of the apparent formation of the neutral radical C5H6N˙ is reported. 相似文献
53.
Krzysztof Bujnowski Ludwik SynoradzkiEckhard Dinjus Thomas ZevacoEwa Augustynowicz-Kope? Zofia Zwolska 《Tetrahedron》2003,59(11):1885-1893
Within the study covering the search for new methods of synthesis of rifamycin antibiotics, the reactions of 3-formylrifamycin SV (2) with primary amines or ammonia were studied. In the reaction of 2 with methylamine, unstable 3-methyliminomethylrifamycin SV (8) was formed, which was further oxidised to stable 3-methyliminomethylrifamycin S (9). In the reaction of 2 with ammonia, N,15-didehydro-15-deoxo-pyrimido-(4,5-b)rifamycin SV (10), a new compound with a chromophore system enlarged by a pyrimidine ring, was obtained. The product of its reduction with sodium borohydride—(11)—was also isolated. The structures of the compounds and an explanation of the synthesis mechanism have been proposed on the basis of mass spectrometry results as well as (1D) and (2D) 1H- and 13C NMR analysis. In vitro antituberculous activity of the new compounds have been investigated. 相似文献
54.
Henryk Foks Mieczysław Janowiec Zofia Zwolska Ewa Augustynowicz-Kopeć 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):2519-2526
2,2′-Sulfinyl-bis(4-methyl phenol) 3 and it's thio derivative have been synthesized in this work. The reduction process of sulfoxide 3 to its thio derivative 5 was accomplished in the presence of Zn/AcOH/SiO2, under microwave irradiation. The structures have been confirmed by spectroscopic (IR, 1HNMR, 13CNMR) and single crystal x-ray diffraction methods. 2,2′-Sulfinyl-bis(4-methyl phenol) 3 crystallizes in the space group Cc of the monoclinic system with four molecules in the unit cell of dimensions a = 11.425(2) Å, b = 13.530(2) Å, c = 9.5215(17) Å, β = 117.289(4) Å, and 2,2′-thio-bis(4-methyl phenol) 5 crystallizes in the space group P 212121 of the orthorhombic system with four molecules in the unit cell of dimensions a = 9.021(1) Å, b = 10.523(2) Å, c = 13.607(2) Å, α = 90. The structures have been refined to final values for the crystallographic R factor of 0.0189(3) and 0.0248(5) based on 2999 and 3720 observed independent reflections respectively. 相似文献
55.
Maciej Chowaniak Marcin Niemiec Zhiqiang Zhu Naim Rashidov Zofia Grdek-Szostak Anna Szelg-Sikora Jakub Sikora Maciej Kubo Salimzoda Amonullo Fayzullo Usmon Mamur Mahmadyorzoda Agnieszka Jzefowska Andrzej Lepiarczyk Florian Gambu 《Molecules (Basel, Switzerland)》2021,26(12)
Natural products have always enjoyed great popularity among consumers. Wild tea is an interesting alternative to tea from intensive plantations. The term “wild tea” is applied to many different varieties of tea, the most desirable and valued of which are native or indigenous tea plants. Special pro-health properties of wild tea are attributed to the natural conditions in which it grows. However, there are no complex studies that describe quality and health indicators of wild tea. The aim of this research was to evaluate the quality of wild and cultivated green tea from different regions of China: Wuzhishan, Baisha, Kunlushan, and Pu’Er. The assessment was carried out by verifying the concentration of selected chemical components in tea and relating it to the health risks they may pose, as well as to the nutritional requirements of adults. Wild tea was characterized by higher micronutrient concentration. The analyzed teas can constitute a valuable source of Mn in the diet. A higher concentration of nitrates and oxalates in cultivated tea can be associated with fertilizer use. The analyzed cultivated tea was a better source of antioxidants with a higher concentration of caffeine. There were no indications of health risks for wild or cultivated teas. 相似文献
56.
Alan R. Katritzky Zofia Dega-Szafran Ragulan Ramanathan John R. Eyler 《Journal of mass spectrometry : JMS》1994,29(2):96-101
Ion—molecule reactions in toluene, toluene-d8, pyridine, 4-methyl-, 4-ethyl- and 4-terr-butylpyridine and quinoline and their mixtures were studied by ICR mass spectrometry at 10-7 Torr (1 Torr = 133.3 Pa). The reactions of benzyl (m/z 91), benzyl-d7 (m/z 98), methylbenzyl (m/z 105), and azabenzyl (m/z 92) ions with pyridines and quinoline were observed. The reactions of protonated pyridines with unprotonated molecules leading to homoconjugated ions (BHB)+ were detected. 相似文献
57.
Anna Michnik Aleksandra Kłos Zofia Drzazga 《Journal of Thermal Analysis and Calorimetry》2004,77(1):269-277
Protein unfolding events were studied by differential scanning calorimetry (DSC) for bovine serum albumin (BSA) aqueous solutions
exposed to radio-frequency radiation. No immediate effect of this radiation on thermal unfolding of BSA was observed. The
differences between irradiated and control samples have appeared during the storage of BSA solution. The irradiated samples
changed faster than non-irradiated. Our results indicated that the age-related changes were stronger for 3.5 and 5 MHz than
for 247 MHz frequency and dependent on energy power of radiation. Deconvolution of DSC traces allowed to study the effect
of radio-frequency radiation on each component transition.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
58.
Zofia Rzączyńska Anna Danczowska-Burdon Justyna Sienkiewicz-Gromiuk 《Journal of Thermal Analysis and Calorimetry》2010,101(2):671-677
Pyridine-2,5-dicarboxylic acid, known as isocinchomeric acid is one of six isomers containing two carboxylic groups. Light
lanthanide (III) complexes with pyridine-2,5-dicarboxylic acid with general formula Ln2L3·nH2O, where n = 8, 9, were obtained. Their thermal and spectroscopic properties were studied. Sodium salt was obtained as Na2L·H2O. Hydrated complexes of La(III), Ce(III), Pr(III), Nd(III), Sm(III), Eu(III) and Gd(III) are stable to 313–333 K, whereas
Na2L·H2O is stable to about 333 K. Dehydration process for all compounds runs in one stage, next they decompose into appropriate
lanthanide oxalates, oxocarbonates carbonates and finally to metal oxides. Bands of νCOOH vibrations at 1736 and 1728 cm−1 disappear on complex spectra and νas and νs of COO− groups appear thus indicating that complexation process took place. 相似文献
59.
Accurate oxidation potentials for organic compounds are critical for the evaluation of thermodynamic and kinetic properties of their radical cations. Except when using a specialized apparatus, electrochemical oxidation of molecules with reactive radical cations is usually an irreversible process, providing peak potentials, E(p), rather than thermodynamically meaningful oxidation potentials, E(ox). In a previous study on amines with radical cations that underwent rapid decarboxylation, we estimated E(ox) by correcting the E(p) from cyclic voltammetry with rate constants for decarboxylation obtained using laser flash photolysis. Here we use redox equilibration experiments to determine accurate relative oxidation potentials for the same amines. We also describe an extension of these experiments to show how relative oxidation potentials can be obtained in the absence of equilibrium, from a complete kinetic analysis of the reversible redox kinetics. The results provide support for the previous cyclic voltammetry/laser flash photolysis method for determining oxidation potentials. 相似文献
60.
The paper proposes a new method for amino acid determination which can be applied for amino acid profiling in solutions for parenteral nutrition. The MEKC method based on a mixed micellar system was developed for the separation of 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) derivatized amino acids. Background electrolyte was based on tris-borate buffer with high alkaline pH. Sodium dodecyl sulfate micelles were modified using 1,2-hexanediol as a co-surfactant. The effect of the modifier on amino acid migration was studied with respect to hydrophobicity of the analytes. The modifier appeared to be suitable to improve the separation of AQC-tagged amino acids without an adverse effect on buffer ionic strength or EOF velocity. The method was successfully validated and applied for amino acid profiling in medicinal preparations for parenteral nutrition. The results obtained were compared with a reference chromatographic method (amino acid analyser). 相似文献