Monitoring dendrimer conformational transition using 19F and 1H2O NMR

The conformational transition of a fluorinated amphiphilic dendrimer is monitored by the 1H signal from water, alongside the 19F signal from the dendrimer. High‐field NMR data (chemical shift δ, self‐diffusion coefficient D, longitudinal relaxation rate R1, and transverse relaxation rate R2) for both dendrimer (19F) and water (1H) match each other in detecting the conformational transition. Among all parameters for both nuclei, the water proton transverse‐relaxation rate R2(1H2O) displays the highest relative scale of change upon conformational transition of the dendrimer. Hydrogen/deuterium‐exchange mass spectrometry reveals that the compact form of the dendrimer has slower proton exchange with water than the extended form. This result suggests that the sensitivity of R2(1H2O) toward dendrimer conformation originates, at least partially, from the difference in proton exchange efficiency between different dendrimer conformations. Finally, we also demonstrated that this conformational transition could be conveniently monitored using a low‐field benchtop NMR spectrometer via R2(1H2O). The 1H2O signal thus offers a simple way to monitor structural changes of macromolecules using benchtop time‐domain NMR. Advanced techniques (high‐resolution NMR, hydrogen/deuterium exchange MS) have been used to detect the concentration‐dependent conformational transition of a fluorinated dendrimer. However, this conformational transition could be monitored in a much more straightforward way using low‐field time‐domain benchtop NMR.