Conformational transition of a non-associative fluorinated amphiphile in aqueous solution. II. Conformational transition vs. supramolecular assembly

Abstract

Unlike many known amphiphiles, the fluorinated amphiphilic dendrimer studied in this work demonstrated a concentration-dependent conformational transition rather than micellization or assembly. Hydrophobic and hydrophilic interactions with water were suggested as the most probable driving force of this transition.This assumption was consistent with the observed 19 F chemical shift changes of the dendrimer compared to a known micelle-forming fluorinated amphiphile. Since water is an important factor in the process, trends of the concentration-dependent changes in water proton transverse relaxation rate served as an indicator of structural changes and/or supramolecular assembly. The conformational transition process was also confirmed by ion-mobility mass-spectrometry. We suggested that structural features, namely, steric hindrances, prevented the micellization/assembly of the dendrimer of this study. This conclusion might inform the approach to develop novel unconventional amphiphiles. † Electronic supplementary information (ESI) available: Water proton transverse relaxation rates vs. concentration of uorinated dendrimer, sodium octanoate and a-cyclodextrin; mass-spectra of uorinated dendrimer at different concentrations. See

Monitoring dendrimer conformational transition using 19F and 1H2O NMR

“…Figure presents the four 19 F and 1 H 2 O NMR parameter pairs versus the 19 FIT‐27 concentration, C ( 19 FIT‐27). All eight parameters reveal a gradual transition as C ( 19 FIT‐27) increases from 0.2 to 100 mM, with a transition point of ~10 mM, consistent with our previous study . Further, for three pairs, including the chemical shift pair, the self‐diffusion coefficient pair and the transverse relaxation rate pair, the 19 F and 1 H 2 O signals show the same trend.…”

“…The dashed vertical line in each panel indicates the approximate transition point, 10 mM. δ ( 19 F) and R 2 ( 1 H 2 O) data have been presented in our previous work . They are shown here again for side‐by‐side comparison of 19 F and 1 H 2 O data…”

“…It is worth noting that the nonlinear profile and the associated transition point of each NMR parameter are not simply caused by higher concentration of 19 FIT‐27, and thereby higher fraction of water molecules in the hydration layer. We have previously demonstrated, using a variety of solutes, that when there is neither conformational transition nor association, R 2 ( 1 H 2 O) increases linearly with the concentration of the solute …”

“…Previously, we have used the 19 F chemical shift δ ( 19 F) and the 1 H 2 O transverse relaxation rate R 2 ( 1 H 2 O) to monitor the conformational transition of 19 FIT‐27 . In this work, we systematically compared the solvent 1 H 2 O NMR signal with the solute 19 F NMR signal in monitoring the conformational transition of 19 FIT‐27 using high‐field NMR.…”

Inspecting Insulin Products Using Water Proton NMR. I. Noninvasive vs Invasive Inspection

“…We have applied w NMR to a variety of systems, including biomaterials, 13,14 surfactants, 15 small molecules, 16 nanoparticles, 17 dendrimers, 12,18 insulin, 2,19 proteins, 15,20,21 monoclonal antibodies, 22,23 vaccine adjuvants 24,25 and vaccines. 26 We also discussed applications of w NMR in the development, 27,28 inspection, 29 and distribution 30 of drugs and vaccines.…”