Formation of nanoscale supramolecular aggregates in cysteine-silver nitrate solutions

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.