The Au containing nanocomposites were synthesized by UV irradiation followed by the thermal treatment of chitosan oligomer solutions doped by HAuCl 4 . The size of the formed gold nanoparti cles depends on the concentration of the dopant, which is proved by UV-Vis absorption spectrosco py and small angle X ray scattering (SAXS). The antioxidant activity of the gold nanoparticles with respect to hydroxy radicals significantly depends on the specific surface of the particles, which was found using the secondary radical spin trapping technique. The change in the • OH radical concen tration was monitored by the intensity of the ESR signal of the adduct of the spin trap (α phenyl N tert butylnitrone) with the Me • radicals formed in the reaction of • OH with DMSO.It is known 1 that gold nanoparticles exhibit high cata lytic activity in some oxidation reactions, such as low temperature CO oxidation, whereas gold as a compact metal is chemically inactive because of both the size effect and the character of interaction of the metal nano particles and support accompanied by the charge transfer between them. A change in the magnetic properties of metals in the nanosized state is of special interest. Previ ously 2 the superparamagnetic behavior of the palladium and gold nanoparticles incorporated into the polymer matrix of polyvinylpyrrolidone has been revealed, al though palladium is weakly paramagnetic and gold in the block state is a typical diamagnetic. Ferromagnetism (ferromagnetic spin polarization) of the gold nanoparticles was experimentally confirmed. 3 Similar changes in the pro perties of the metal on going to the nanosized state can be due to the dependence of the electronic structure on the particle size. The theoretical substantiation of the specif ic features of the electron states of the Au nanoparticles and the calculations proving the dependences of the Fermi energy on the particle size have been presented earlier. 4,5The interaction of the gold nanoparticles and the Au 3 and Au 13 clusters with organic radicals in alkanethiol hybrid systems was theoretically simulated. 4 Some pub lications concern the antioxidation effect of the gold nano particles stabilized by solutions of high molecular weight chitosan 6 and dendrimers 7 with respect to hydroxy radi cals. However, when studying these nanocomposites, a possible decrease in the hydroxy radical concentration due to intense chitosan destruction by hydrogen peroxide via the radical mechanism was ignored. 8,9 To exclude this effect, oligosaccharide of chitosan was used instead of the high molecular weight chitosan itself to stabilize the nanoparticles. Our preliminary experiments showed that the oligomer used underwent no changes under the experimental conditions.The purpose of this work is the ESR spectral study of the antioxidant properties of the gold nanoparticles in oligochitosan solutions depending on the particle size. ExperimentalThe gold nanocomposites were obtained in aqueous solutions of the chitosan oligomer doped by chloroauric acid (HAuCl 4 ) w...
Under laboratory conditions, the spores of a xerotolerant Streptomyces odorifera strain germinated in brown semidesert soil even at extremely low soil water pressure (P = -96.4 MPa, -964 atm, a w 0.50); the plantlets increased in length and formed mycelium, on which a new generation of spores was produced (a complete development cycle of the actinomycetes-from a spore to the formation of new spores-passed). The duration of the first cycles of the actinomycetes' development varied from 13 days at P = -27 atm to 57 days at P = -964 atm and was directly proportional to the absolute value of the soil water pressure (P). In the first cycles of the act inomycetes' development, the rate of increase of the concentration of the germinated spores and mycelium, as well as the logarithms of the mycelium to germinated spore concentration ratios, was inversely propor tional to the logarithm of P. These relationships indicated that the energy state of the water determined its availability to soil biota and, hence, the activity of its physiological and biochemical processes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.