Self-assembly and gel formation processes in an aqueous solution of L-cysteine and silver nitrate (original) (raw)
Related papers
On Molecular Gelation Mechanism of L-Cysteine Based Hydrogel
Nanoscience and Nanoengineering Vol. 1(1), pp. 23 - 35 , 2013
A method for preparing a supramolecular hydrogel composed of a mixture of L-cysteine, and silver nitrate is reported. The main features of the hydrogel are gelation at low content of the dispersed phase (~ 0.01%) induced by addition of various salts (sulfates, sulfites, chlorides, bromides, and others) and thixotropic behavior. On the basis of experimental data, the mechanism of gelation is suggested. It is assumed that filament-like aggregates in the system are formed from silver mercaptide zwitterions due to noncovalent bonding as a result of self-assembly processes, addition of a salt leads to physical cross-linking, and gel network formation. An atomistic computer model is developed to confirm the supposed mechanism of gelation. It is established that resulting molecular configurations are stabilized by the interactions of –NH3+ and –C(O)O– groups of silver mercaptide zwitterions comprising neighboring clusters. These assumptions are taken as a basis of a mesoscopic model to study the processes of nucleation and growth of filament-like aggregates on a large spatial scale.
Soft Matter, 2017,13, 5168-5184 , 2017
We discuss results of experimental studies of the processes of gelation in aqueous solutions of silver nitrate with L-cysteine and its derivatives. We focus on understanding what determines if these small molecules will self-assemble in water at their extremely low concentration to form a gel. A mechanism of gel formation in a cysteine-silver solution (CSS) is proposed. The analysis of the results indicates that filamentary aggregates of a gel network are formed via interaction of NH3 + and C(O)O-groups that belong to neighboring silver mercaptide (SM) aggregates. In its turn, formation of sulphur-silver bonds between silver mercaptide molecules are responsible for self-assembling these molecules into SM aggregates which can be considered as supramonomers. Free polar groups located on the surfaces of the aggregates can form hydrogen bonds with water molecules, which explains the unique ability of CSS hydrogels to trap water at low concentrations of low-molecular-weight hydrogelators.
Supramolecular Hydrogels Based on Silver Mercaptide. Self-Organization and Practical Application
Macromolecular Symposia Volume 316, Issue1, 97-107 (2012), 2012
A novel supramolecular thixotropic hydrogel based on low-concentrated solutions of L-cysteine and silver nitrate is synthesized. Self-organization and gelation in the system are studied experimentally by means of UV-vis and FTIR spectroscopy, dynamic light scattering, rotational viscometry, transmission electron microscopy, as well as theoretically by quantum mechanics and molecular dynamics. A mechanism of the formation of the supramolecular hydrogel is suggested, potential application for medicinal purposes is considered.
Soft Matter, 2022,18(39), 7524-7536, 2022
We use fully atomistic, quantum mechanics and mesoscopic simulations to investigate multiscale structure formation in a supramolecular system based on aqueous solutions of silver nitrate with L-cysteine (CSS). Fully atomistic modeling reveals that silver mercaptide clusters are formed in solution at the stage of aging, which has a pronounced ''core-shell'' structure. The core is formed due to the bonding of SAg groups of silver mercaptide (SM) zwitterions while the shell consists of NH 3 + and C(O)O À groups. Self-assembly of large-scale aggregates in CSS occurs due to the interaction of SM functional groups located on the surface of the clusters, which allows them to be considered supramonomers. Quantum-mechanical calculations reveal additional insight into the intermolecular interaction of L-cysteine with the components of the system. The data on the structure and properties of supramonomers are used to develop and parameterize a mesoscopic CSS model supplemented with allowance for salt concentration. In the mesoscopic model, supramonomers are presented as ''sticky spheres'', the interaction between which is determined by short-range and screened Coulomb potentials. Depending on the salt concentration, all structural transitions typical of CSS are observed: the formation of a stabilized colloidal dispersion, the filamentary aggregates of a gel network, the formation of large-scale unbound aggregates, and precipitation. These stages qualitatively reproduce the experimentally observed behavior of a real solution.
Synthesis and characterization of silver cluster particles in hydrogels
A chitosan-based hydrogel network was crosslinked with genipin; the crosslinked and uncrosslinked hydrogels were prepared and studied. Uniformly distributed silver cluster particles (AgCPs) were prepared using these hydrogel networks as a carrier via in situ reduction of silver nitrate (AgNO 3 ) in the presence of sodium borohydride (NaBH 4 ) as a reducing agent; UV irradiation reduction was also done. Fourier transform infrared (FTIR) spectroscopy studies of the hydrogels gave results on the decree of crosslinking and some indication on the presence of the AgCPs. The spectrophotometric analysis indicated the presence of AgCPs, as a peak appeared around 400 nm. The microscopy analysis gave images of the presence of AgCPs and their size; it showed that the crosslinked hydrogels have uniformly distributed AgCPs and as the crosslinking increased, the AgCPs size decreased. The studies on the increasing concentration of AgNO 3 solution gave an increase AgCPs size; the maximum size of AgCPs clusters was ∼ 0.2 micron in uncrosslinked chitosan. It was demonstrated, by using Escherichia coli ( E. coli ) bacterium, that the AgCPs hydrogel can be effectively employed as antibacterial material.
Colloid J (2011) 73: 482., 2011
The process of the emergence of gel network in a cystein-silver solution is studied by full-atom molecular dynamics. It is shown that, because of the formation of donor-acceptor sulfur-silver bonds, clusters are formed by zwitterions and cations of silver mercaptide followed by the formation of filament-like aggregates. The analysis of formed molecular configurations demonstrates that filament-like aggregates are stabilized by virtue of the interaction between −NH3+ and −C(O)O− groups that belong to the particles of silver mercaptide comprising neighbor clusters. The absorption UV spectra of various aggregates formed from particles of silver mercaptide are investigated by the quantum-mechanical ZINDO/1 method.
Simulation of Gelation Process in Cysteine–Silver Solution by Dissipative Particle Dynamics Method
Baburkin, P.O., Komarov, P.V., Khizhnyak, S.D. et al. Simulation of gelation process in cysteine–silver solution by dissipative particle dynamics method. Colloid J 77, 561–570 (2015) , 2015
The results of simulating gelation in a cysteine–silver solution have been presented. All calcula� tions have been carried out in terms of the dissipative particle dynamics method. In the developed model, the introduction of a salt, which initiates gelation, is taken into account implicitly by setting the parameters of the interaction between polar groups of cysteine and a solvent. It has been shown that fibers of gel network are formed in a narrow range of the initiating salt concentration due to weakened interaction of polar groups of cysteine with a solvent.
Baburkin, P.O., Komarov, P.V., Malyshev, M.D. et al. Colloid J 79, 577–587 (2017) , 2017
Structural transformations occurring in aqueous L-cysteine−silver-nitrate mixed solutions (CSSs) upon the addition of an initiating salt have been studied within the framework of mesoscopic simulation using the dissipative particle-dynamics method. Diffusion of silver mercaptide clusters is decelerated, and metastable chain aggregates thereof are formed in a narrow concentration range of the salt, probably due to the transition into a gel-like state. The results obtained are in qualitative agreement with the experimentally observed behavior of CSSs.
A supramolecular medical hydrogel based on L-cysteine and silver ions
Polym. Sci. Ser. A 53, 820 (2011), 2011
A novel supramolecular thixotropic gel based on low-concentration aqueous solutions of L-cysteine and silver nitrate is synthesized. Self-organization and gel formation in the system of interest is studied by means of UV and IR spectroscopy, transmission electron microscopy, dynamic light scattering, and rotational viscometry. A model of the supramolecular gel is suggested. Possible applications for medicinal purposes are considered.
Formation of nanoscale supramolecular aggregates in cysteine-silver nitrate solutions
Nanotechnologies in Russia volume 3, pages 716–721 (2008), 2008
The gelling process in an aqueous solution of cysteine-silver nitrate was studied within the ZINDO/1 quantum chemistry method. As shown previously, silver mercaptide (SM) molecules are formed in the first self-assembly stage in such systems, based on which, supramolecular aggregates (SA) can be formed. The SA stability was studied as a function of the number of SM molecules at their various relative orientations in an aqueous solution. It was found that SM molecules can form linear nanoscale supramolecular oligomers such as [Ag-S-Cys] n with a relatively low interaction energy (∼20 kcal/mol) due to noncovalent bonds. This is one of the answers to the question why thixotropic physical gels can be formed in cysteine-silver nitrate solutions.