Single-molecule force spectroscopy reveals cation-π interactions in aqueous media are highly affected by cation dehydration

• Main Authors: Di, Weishuai, Xue, Kai, Cai, Jun, Zhu, Zhenshu, Li, Zihan, Fu, Hui, Lei, Hai, Hu, Wenbing, Tang, Chun, Wang, Wei, Cao, Yi
• Other Authors: School of Physical and Mathematical Sciences
• Format: Article
• Language: English
• Published: 2023
• Subjects: Science::Physics; Aqueous Media; Binding Mechanisms
• Online Access: https://hdl.handle.net/10356/169314
• Institution: Nanyang Technological University

Cation-π interactions underlie many important processes in biology and materials science. However, experimental investigations of cation-π interactions in aqueous media remain challenging. Here, we studied the cation-π binding strength and mechanism by pulling two hydrophobic polymers with distinct cation binding properties, i.e., poly-pentafluorostyrene and polystyrene, in aqueous media using single-molecule force spectroscopy and nuclear magnetic resonance measurement. We found that the interaction strengths linearly depend on the cation concentrations, following the order of Li^{+}<NH_{4}^{+}<Na^{+}<K^{+}. The binding energies are 0.03-0.23 kJ mol^{-1} M^{-1}. This order is distinct from the strength of cation-π interactions in gas phase and may be caused by the different dehydration ability of the cations. Taken together, our method provides a unique perspective to investigate cation-π interactions under physiologically relevant conditions.