Tunable dynamic hydrophobic attachment of guest molecules in amphiphilic core–shell polymers

Abstract

In this study, synthesis and dynamic properties of amphiphilic core-shell polymers are reported as monitored through their interaction with small amphiphilic molecules. Brush-like structures are formed with a hydrophobic core surrounded by a hydrophilic shell utilizing controlled radical addition-fragmentation chain transfer (RAFT) polymerization of macromonomers consisting of linear polyglycerol chains attached to alkylene methacrylate. Continuous wave electron paramagnetic resonance (CW EPR) spectroscopy is employed to study how the amphiphilic, paramagnetic spin probe 16-DSA (16-doxyl stearic acid) interacts with polymers of different alkylene chain lengths in their hydrophobic cores and different polyglycerol chain lengths in their hydrophilic shells. The spin probe exhibits dynamic hydrophobic attachment to the polymers and reveals an indirect, dynamics-based view of polymer effects such as temperature response, aggregation and ligand binding properties. Increasing the hydrophobic alkylene chain length in the polymers alters the physical properties of the core region significantly. A large set of controllable functional polymer properties can be adjusted by the degree of polymerization and alkylene spacer length. Partial aggregation of the polymers further modifies the binding properties. Applying dynamic light scattering (DLS), transmission electron microscopy (TEM) and molecular dynamic (MD) simulations, the complex dynamic behavior found with EPR spectroscopy was further complemented and verified

Exploring the pH-Induced Functional Phase Space of Human Serum Albumin by EPR Spectroscopy

“…Exemplary simulations on 16HSA 1:0 400 µM and 16HSA 2:1 400 µM have been conducted with the EasySpin [83] program package v5.2.11 in MATLAB v7.7.0 (R2008b) for extracting all emerging subspectra (F i (B) a, f, b 1 , b 2 ) and the magnetic gand A-tensors (Supplementary Material S4) similar to a previous study [84]. This was considered as necessary for the construction of order parameters S and wobbling angles γ.…”

A Platform of Phenol‐Based Nitroxide Radicals as an “EPR Toolbox” in Supramolecular and Click Chemistry

“…For the large toolbox of SPs and SLs, 17 currently not commercially available PD-x (x = 13, 14,16,34,35,36,37,38,42,[52][53][54][55][56][57][58]62; see Schemes S2, S6, S8, S10 and S12-S14), were Figure 11) were obtained in good to very good yields (73-93 %) depending on the type of Steglich esterification and the reaction time (3 h-24 h) using mild reaction conditions (0°C-RT). For further conclusions, Figure 12 summarizes all water solubilities in one graph, which makes direct comparisons easier.…”

“…5‐DSA, 16‐DSA), Frémy's salt, TEMPO and PROXYL derivatives, were widely used for measuring intramolecular distances between supramolecular systems, e. g . protein‐protein interactions, for loading/release capability studies using charged/core‐shell polymers, for constructing supramolecular systems, e. g . polymers, dendrons, peptides etc., as pH‐sensitive and target spin traps,, as NMR shifting reagents,, for in vivo oximetry,, etc.…”

“…Its dianion with its very narrow lines has only in recent years been more reliably used as a versatile, dianionic spin probe in charged systems in particular in our lab. [30,31] Beside MR-based spin probing (noncovalent interactions of radical and system of interest) and spin labeling (chemical attachment of radical to system of interest) assays using target probes and spin labels, different types of nitroxide radicals, e. g. DOXYL-stearic acids (DSA, e. g. 5-DSA, 16-DSA), Frémy's salt, TEMPO and PROXYL derivatives, were widely used for measuring intramolecular distances between supramolecular systems, e. g. protein-protein interactions, [32] for loading/release capability studies using charged/core-shell polymers, [33][34][35] for constructing supramolecular systems, e. g. polymers, dendrons, peptides etc., [36][37][38] as pH-sensitive and target spin traps, [39,40] as NMR shifting reagents, [41,42] for in vivo oximetry, [43,44] etc. The exploitation of more or improved application ranges depends on new nitroxide-based synthetic pathways and application of modern MR methods.…”

Fatty Acid Triangulation in Albumins Using a Landmark Spin Label

“…This software comprises routines that implement the theory of slow tumbling nitroxides as mainly pioneered by Freed and coworkers . Similar to a procedure reported recently all MATLAB codes were optimized for 4‐component nitroxide spectra comprising three immobilized components ( b 1 , b 2 and b 3 ) and a single free component ( f ). For successful reconstructions of experimental spectra (see Table S6 and Figure S13) starting values for magnetic parameters of MTSSL were taken from Steinhoff et al .…”