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91.
Fritscher J Artin E Wnuk S Bar G Robblee JH Kacprzak S Kaupp M Griffin RG Bennati M Stubbe J 《Journal of the American Chemical Society》2005,127(21):7729-7738
Ribonucleotide reductases (RNRs) catalyze the conversion of nucleotides to deoxynucleotides providing the monomeric precursors required for DNA replication and repair. The class I RNRs are composed of two homodimeric subunits: R1 and R2. R1 has the active site where nucleotide reduction occurs, and R2 contains the diiron tyrosyl radical (Y*) cofactor essential for radical initiation on R1. Mechanism-based inhibitors, such as 2'-azido-2'-deoxyuridine-5'-diphosphate (N(3)UDP), have provided much insight into the reduction mechanism. N(3)UDP is a stoichiometric inactivator that, upon interaction with RNR, results in loss of the Y* in R2 and formation of a nitrogen-centered radical (N*) covalently attached to C225 (R-S-N*-X) in the active site of R1. N(2) is lost prior to N* formation, and after its formation, stoichiometric amounts of 2-methylene-3-furanone, pyrophosphate, and uracil are also generated. On the basis of the hyperfine interactions associated with N*, it was proposed that N* is also covalently attached to the nucleotide through either the oxygen of the 3'-OH (R-S-N*-O-R') or the 3'-C (R-S-N*-C-OH). To distinguish between the proposed structures, the inactivation was carried out with 3'-[(17)O]-N(3)UDP and N* was examined by 9 and 140 GHz EPR spectroscopy. Broadening of the N* signal was detected and the spectrum simulated to obtain the [(17)O] hyperfine tensor. DFT calculations were employed to determine which structures are in best agreement with the simulated hyperfine tensor and our previous ESEEM data. The results are most consistent with the R-S-N*-C-OH structure and provide evidence for the trapping of a 3'-ketonucleotide in the reduction process. 相似文献
92.
Kamil Piwowarek Edyta Lipi&#x;ska Elbieta Ha&#x;-Szyma&#x;czuk Anna Maria Kot Marek Kieliszek Sylwia Bonin 《Molecules (Basel, Switzerland)》2021,26(13)
Propionic acid bacteria are the source of many metabolites, e.g., propionic acid and trehalose. Compared to microbiological synthesis, the production of these metabolites by petrochemical means or enzymatic conversion is more profitable. The components of microbiological media account for a large part of the costs associated with propionic fermentation, due to the high nutritional requirements of Propionibacterium. This problem can be overcome by formulating a medium based on the by-products of technological processes, which can act as nutritional sources and at the same time replace expensive laboratory preparations (e.g., peptone and yeast extract). The metabolic activity of P. freudenreichii was investigated in two different breeding environments: in a medium containing peptone, yeast extract, and biotin, and in a waste-based medium consisting of only apple pomace and potato wastewater. The highest production of propionic acid amounting to 14.54 g/L was obtained in the medium containing apple pomace and pure laboratory supplements with a yield of 0.44 g/g. Importantly, the acid production parameters in the waste medium reached almost the same level (12.71 g/L, 0.42 g/g) as the medium containing pure supplements. Acetic acid synthesis was more efficient in the waste medium; it was also characterized by a higher level of accumulated trehalose (59.8 mg/g d.s.). Thus, the obtained results show that P. freudenreichii bacteria exhibited relatively high metabolic activity in an environment with apple pomace used as a carbon source and potato wastewater used as a nitrogen source. This method of propioniate production could be cheaper and more sustainable than the chemical manner. 相似文献
93.
Aleksandra Podgrska Anna Pu cion-Jakubik Anita Grodzka Sylwia K. Naliwajko Renata Markiewicz- ukowska Katarzyna Socha 《Molecules (Basel, Switzerland)》2021,26(13)
Mercury (Hg) can enter the human body through the respiratory tract and digestive system, but also through the skin. Sources of Hg in the environment can be natural processes, but also human activities, including agriculture, chemical, and pharmaceutical industries. Hg can also enter the body through food, but also with cosmetics that are used for a long time. Therefore, the aim of this study was to evaluate the Hg content in 268 randomly selected cosmetics: Natural and conventional, for face and body. Hg content was determined using an atomic absorption spectrometer (AMA 254, Leco, Prague, Czech Republic). It was shown that the face preparations were characterized by a significantly higher Hg content than the body preparations. No differences in the content of the tested element were found between natural and conventional preparations. Hg could be detected in all samples with concentrations measured from 0.348 to 37.768 µg/kg. 相似文献
94.
Sylwia Zi&#x;ba Agata Piotrowska Adam Mizera Pawe&#x; &#x;awniczak Karolina H. Markiewicz Andrzej Gzella Alina T. Dubis Andrzej &#x;api&#x;ski 《Molecules (Basel, Switzerland)》2021,26(15)
The increase in conductivity with temperature in 1H-pyrazol-2-ium 2,6-dicarboxybenzoate monohydrate was analyzed, and the influence of the mobility of the water was discussed in this study. The electric properties of the salt were studied using the impedance spectroscopy method. WB97XD/6-311++G(d,p) calculations were performed, and the quantum theory of atoms in molecules (QTAiM) approach and the Hirshfeld surface method were applied to analyze the hydrogen bond interaction. It was found that temperature influences the spectroscopic properties of pyrazolium salt, particularly the carbonyl and hydroxyl frequencies. The influence of water molecules, connected by three-center hydrogen bonds with co-planar tetrameters, on the formation of structural defects is also discussed in this report. 相似文献
95.
96.
Amanda Grylewicz Kacper Szyma&#x;ski Dominika Darowna Sylwia Mozia 《Molecules (Basel, Switzerland)》2021,26(9)
Ultrafiltration polyethersulfone (PES) membranes were prepared by wet phase inversion. Commercial halloysite nanotubes (HNTs) in the quantities of 0.5 wt% vs. PES (15 wt%) were introduced into the casting solution containing the polymer and different solvents: N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), or 1-methyl-2-pyrrolidinone (NMP). The type of solvent influenced the membranes’ morphology and topography, as well as permeability, separation characteristics, and antifouling and antibacterial properties. The membranes prepared using DMA exhibited the loosest cross-section structure with the thinnest skin and the roughest surface, while the densest and smoothest were the DMF-based membranes. The advanced contact angles were visibly lower in the case of the membranes prepared using DMF compared to the other solvents. The highest water permeability was observed for the DMA-based membranes, however, the most significant effect of the modification with HNTs was found for the NMP-based series. Regardless of the solvent, the introduction of HNTs resulted in an improvement of the separation properties of membranes. A noticeable enhancement of antifouling performance upon application of HNTs was found only in the case of DMF-based membranes. The study of the antibacterial properties showed that the increase in surface roughness had a positive effect on the inhibition of E. coli growth. 相似文献
97.
Dr. Katarzyna Pamin Dr. Edyta Tabor Sylwia Górecka Prof. Władysław W. Kubiak Dr. Dorota Rutkowska-Zbik Dr. Jan Połtowicz 《ChemSusChem》2019,12(3):684-691
Three generations of cobalt porphyrins were synthesized, physicochemically characterized by FTIR and UV/Vis spectroscopy as well as cyclic voltammetry and applied as catalysts in the oxidation of cycloalkanes with atmospheric molecular oxygen under mild conditions. All examined catalysts were active in the tested reaction, and their catalytic activity varied with the nature and number of substituents on the porphyrin ring. Introduction of electron-withdrawing or electron-donating substituents at the porphyrin rings increases the activity of metalloporphyrin complexes. It was found, for the first time, that generation II cobalt porphyrins show higher activity in cycloalkane oxidation than cobalt porphyrins of generation III. The lower catalytic activity of generation III cobalt porphyrins can be attributed to the saddle-shaped deformation of the porphyrin macrocycle. DFT modeling of Co porphyrins and their interactions with molecular oxygen provided explanations for the observed effects. On the basis of prior reports and the obtained results, a reaction mechanism is proposed and discussed. 相似文献
98.
Renata Kasprzyk Beata J. Starek Sylwia Ciechanowicz Dorota Kubacka Joanna Kowalska Jacek Jemielity 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(27):6728-6740
The m7G cap is a unique nucleotide structure at the 5′-end of all eukaryotic mRNAs. The cap specifically interacts with numerous cellular proteins and participates in biological processes that are essential for cell growth and function. To provide small molecular probes to study important cap-recognizing proteins, we synthesized m7G nucleotides labeled with fluorescent tags via the terminal phosph(on)ate group and studied how their emission properties changed upon protein binding or enzymatic cleavage. Only the pyrene-labeled compounds behaved as sensitive turn-on probes. A pyrene-labeled m7GTP analogue showed up to eightfold enhanced fluorescence emission upon binding to eukaryotic translation initiation factor 4E (eIF4E) and over 30-fold enhancement upon cleavage by decapping scavenger (DcpS) enzyme. These observations served as the basis for developing binding- and hydrolytic-activity assays. The assay utility was validated with previously characterized libraries of eIF4E ligands and DcpS inhibitors. The DcpS assay was also applied to study hydrolytic activity and inhibition of endogenous enzyme in cytoplasmic extracts from HeLa and HEK cells. 相似文献
99.
Calorimetry is evaluated for study of the toxic effect of environmental androgens on Schizosaccharomyces pombe cells. The results indicate that androstendione, androstandiendione and dehydrotestosterone inhibited S. pombe heat production rate. Although, the turbidimetric method showed that testosterone (TS) had no influence on growth of S. pombe, calorimetry revealed that there was a shift in growth period in samples with TS. 相似文献
100.