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371.
Measurements of electrochemical (EC) arsenite oxidation demonstrated thatthe arsenite oxidation current increased in the presence of carbonate while the potential of the onset of EC arsenite oxidation exhibited a strong shift toward less positive values. Examination of pH and total carbonate concentration effects on the EC arsenite oxidation parameters showed that they were affected solely by the concentration of carbonate ion CO3(2-), which appeared to form relatively weak mono- and dicarbonate complexes with arsenite. The EC activity of these complexes was determined to be almost an order of magnitude higher than that of free arsenite. However, X-ray absorption fine-structure (XAFS) measurements did not show any changes in the properties of the As(III) inner complexation shell associated with the presence of the bound carbonate ions. It was accordingly concluded that the strength of bonds between the bound carbonate and As(III) is close to that for As(III)-OH- interactions. The acceleration of the oxidation of carbonate-As(III) complexes was hypothesized to be associated with an additional pathway of the formation of As(IV) intermediates, in which the carbonate group present in the As(III) inner shell provides an electron to form a bound carbonate radical and also a good leaving group for facile cleavage from the transient As(IV) species. 相似文献
372.
Alexey V. Samokhvalov Irina V. Safenkova Sergei A. Eremin Artem N. Bonchuk Oksana G. Maksimenko Nikolai N. Sluchanko Anatoly V. Zherdev Boris B. Dzantiev 《International journal of molecular sciences》2022,23(9)
Short oligonucleotides are widely used for the construction of aptamer-based sensors and logical bioelements to modulate aptamer–ligand binding. However, relationships between the parameters (length, location of the complementary region) of oligonucleotides and their influence on aptamer–ligand interactions remain unclear. Here, we addressed this task by comparing the effects of short complementary oligonucleotides (ssDNAs) on the structure and ligand-binding ability of an aptamer and identifying ssDNAs’ features that determine these effects. Within this, the interactions between the OTA-specific G-quadruplex aptamer 1.12.2 (5′-GATCGGGTGTGGGTGGCGTAAAGGGA GCATCGGACA-3′) and 21 single-stranded DNA (ssDNA) oligonucleotides complementary to different regions of the aptamer were studied. Two sets of aptamer–ssDNA dissociation constants were obtained in the absence and in the presence of OTA by isothermal calorimetry and fluorescence anisotropy, respectively. In both sets, the binding constants depend on the number of hydrogen bonds formed in the aptamer–ssDNA complex. The ssDNAs’ having more than 23 hydrogen bonds with the aptamer have a lower aptamer dissociation constant than for aptamer–OTA interactions. The ssDNAs’ having less than 18 hydrogen bonds did not affect the aptamer–OTA affinity. The location of ssDNA’s complementary site in the aptamer affeced the kinetics of the interaction and retention of OTA-binding in aptamer–ssDNA complexes. The location of the ssDNA site in the aptamer G-quadruplex led to its unfolding. In the presence of OTA, the unfolding process was longer and takes from 20 to 70 min. The refolding in the presence of OTA was possible and depends on the length and location of the ssDNA’s complementary site. The location of the ssDNA site in the tail region led to its rapid displacement and wasn’t affecting the G-qaudruplex’s integrity. It makes the tail region more perspective for the development of ssDNA-based tools using this aptamer. 相似文献
373.
Liudmila Gorelova Oleg Vereshchagin Andrey Aslandukov Alena Aslandukova Dar'ya Spiridonova Maria Krzhizhanovskaya Anatoly Kasatkin Leonid Dubrovinsky 《Journal of the American Ceramic Society》2023,106(4):2622-2634
Hydroxylherderite, Ca2Be2P2O8(OH)2, is among the most common beryllophosphates in nature and could play a substantial role in Be geochemical cycle. Hydroxylherderite P–T stability and crystal structure behavior were studied under extreme conditions (up to 750°C/100 GPa) using in situ single-crystal and powder X-ray diffraction and Raman spectroscopy. The mineral demonstrated high stability under high-pressure conditions (up to ∼100 GPa) without any phase transitions. Under high-temperature conditions, it was stable up to about 700°C, when it decomposed with the formation of fluorapatite Ca5(PO4)3F and hurlbutite CaBe2P2O8. The beryllophosphate member of the gadolinite supergroup is the most stable mineral (material) under high-pressure conditions, compared to aluminum-, boro- and beryllosilicates. 相似文献
374.
Sergei V. Egorov Anatoly G. Eremeev Vladislav V. Kholoptsev Ivan V. Plotnikov Kirill I. Rybakov Andrei A. Sorokin Elena Ye. Rostokina Stanislav S. Balabanov 《Journal of the American Ceramic Society》2023,106(2):878-887
ZnO samples with an addition of 0, 0.035, 0.1, and 0.35 mol.% Bi2O3 were microwave sintered at heating rates 10 and 50°C/min to a maximum temperature of 1200°C with zero hold time. The densification curves obtained by optical dilatometry have been studied in their dependence on the dopant concentration and the heating rate. Direct volumetric absorption of microwave radiation resulted in a 50–60°C shift of the densification curves toward low temperatures compared to susceptor-assisted heating. An analysis of the effect of the volumetrically absorbed microwave power on the formation of grain-boundary phases that facilitate densification is presented. 相似文献