Self-organization in l -cysteine-silver acetate-D 2 O solutions at low-concentrations
- PDF / 697,368 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 86 Downloads / 159 Views
1799
Self-organization in L-cysteine—silver acetate—D2O solutions at low-concentrations* A. N. Adamyan, D. V. Vishnevetskii, A. I. Ivanova, S. D. Khizhnyak, and P. M. Pakhomov Tver State University, 33 ul. Zhelyabova, 170100 Tver, Russian Federation. Fax: +7 (482 2) 32 1274. E-mail: [email protected] Supramolecular hydrogels based on solutions of L-cysteine and silver acetate at low-concentrations in heavy water (D2O) were prepared. Processes of self-organization of L-cysteine and silver acetate in plain and heavy water have been investigated using UV spectroscopy, dynamic light scattering, and NMR spectroscopy. A replacement of H2O with D2O causes aging of the cysteine-silver solution, and resulting particles in the solution are larger in size. A possible structure of the supramolecular aggregate was proposed using NMR spectroscopy, and the mechanism of its interaction with the salt anions introduced into the system upon the formation of resulting hydrogels was verified. Key words: plain and heavy water, L-cysteine, silver acetate, self-organization, supramolecular hydrogel.
Recently, hydrogels based on such natural compounds as amino acids, nucleotides, lipids, etc., are gaining more and more attention due to the need for them in biomedicine, pharmacology, and food industry. For instance, amino acid L-cysteine exhibits a wide range of pharmacological activities, while antibacterial and anti-inflammatory properties are characteristic of silver. Thus, investigations of the systems based on these components are not only of scientific, but also of practical interest. It has been found1,2 for aqueous solutions of L-cysteine (L-Cys) and silver nitrate (cysteine-silver solutions (CSS)) that gel formation proceeds therein at low-concentrations (~0.01%). The gel formation also occurs in solutions based on L-Сys and silver acetate (AcOAg).3 The molecule of L-Сys contains three functional groups: amino, thiol, and carboxyl ones. Apparently, exactly the set of these functional groups is responsible for the embodiment of the simplest method for obtaining hydrogels based on low molecular weight compounds via a simple mixing of aqueous solutions of the starting components. The gel formation is affected by chemical natures of both the amino acid and the silver salt. However, there is a question about the role of water itself in the process of structuring the final hydrogel, i.e. are hydrogen bonds established directly between groups in the CSS chains or does water cause any significant effect on the hydrogen bonding? It has been reported1 that mixtures of various * Based on the materials of the XXI Mendeleev Congress on General and Applied Chemistry (September 9—13, 2019, St. Petersburg, Russia).
polar solvents (such as pyridine, DMSO, ethanol, or methanol) with water at the certain ratios lead to the gel formation in CSS. However, the total dielectric constants of mixtures of these solvents are different in this case from the corresponding value for water. At the same time, it is known that the dielectric constant of heavy wat
Data Loading...
