Ag+-Induced Supramolecular Polymers of Folic Acid: Reinforced by External Kosmotropic Anions Exhibiting Salting Out

Biomacromolecules. 2024 Sep 9;25(9):6203-6215. doi: 10.1021/acs.biomac.4c01063. Epub 2024 Aug 17.

Abstract

Introducing kosmotropic salts enhances protein stability and reduces solubility by withdrawing water from the protein surface, leading to 'salting out', a phenomenon we have mimicked in supramolecular polymers (SPs). Under the guidance of Ag+, folic acid (FA) self-assembled in water through slipped-stacking and hydrophobic interactions into elongated, robust one-dimensional SPs, resulting in thermo-stable supergels. The SPs exhibited temperature and dilution tolerance, attributed to the stability of the FA-Ag+ complex and its hydrophobic stacking. Importantly, FA-Ag+ SP's stability has been augmented by the kosmotropic anions, such as SO42-, strengthening hydrophobic interactions in the SP, evident from the enhanced J-band, causing improvement of gel's mechanical property. Interestingly, higher kosmotrope concentrations caused a significant decrease in SP's solubility, leading to precipitation of the reinforced SPs─a 'salting out' effect. Conversely, chaotropes like ClO4- slightly destabilized hydrophobic stacking and promoted an extended conformation of individual SP chain with enhanced solubility, resembling a 'salting in' effect.

MeSH terms

  • Anions* / chemistry
  • Folic Acid* / chemistry
  • Hydrophobic and Hydrophilic Interactions*
  • Polymers* / chemistry
  • Salts / chemistry
  • Silver* / chemistry
  • Solubility*

Substances

  • Folic Acid
  • Anions
  • Polymers
  • Silver
  • Salts