Quantitative Analysis of the Hydrogen Bond Interaction between Tyrosine and a Simulated Cell Membrane by SECM

The hydrogen bond between an amino acid and a negatively charged cell membrane plays significant role in amino acid transport. Electroneutral tyrosine (Tyr) was chosen, and the 3-mercaptopropionic acid self-assembled monolayer (MPA SAM) was constructed as a simulated negatively charged cell membrane. The intermolecular hydrogen bond between Tyr and MPA was expressed as a visual current response by scanning electrochemical microscopy. Analysis of the current response signal with a Langmuir model obtained the binding constant, which quantified the intermolecular hydrogen bond interaction between Tyr and MPA. Furthermore, due to the importance of charge density of membranes, two other SAMs with different negative surface charge densities were established and investigated. Results showed that the larger the charge density of the SAM was, the stronger the hydrogen bond with Tyr was, which was seen by the larger value of the binding constant. This work provided an intuitive perspective for the quantitative analysis of the hydrogen bond between an amino acid and a simulated cell membrane.