Formation of pH‐Resistant Monodispersed Polymer–Lipid Nanodiscs

Polymer lipid nanodiscs are an invaluable system for structural and functional studies of membrane proteins in their near‐native environment. Despite the recent advances in the development and usage of polymer lipid nanodisc systems, lack of control over size and poor tolerance to pH and divalent metal ions are major limitations for further applications. A facile modification of a low‐molecular‐weight styrene maleic acid copolymer is demonstrated to form monodispersed lipid bilayer nanodiscs that show ultra‐stability towards divalent metal ion concentration over a pH range of 2.5 to 10. The macro‐nanodiscs (>20 nm diameter) show magnetic alignment properties that can be exploited for high‐resolution structural studies of membrane proteins and amyloid proteins using solid‐state NMR techniques. The new polymer, SMA‐QA, nanodisc is a robust membrane mimetic tool that offers significant advantages over currently reported nanodisc systems.All under control: A poor tolerance to pH and divalent metal ions and a lack of control over size are major limitations of polymer nanodiscs. A modified styrene maleimide based polymer is demonstrated to form monodispersed nanodiscs with ultrahigh stability towards divalent metal ions over a pH range of 2.5 to 10.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141640/1/anie201712017_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/141640/2/anie201712017-sup-0001-misc_information.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/141640/3/anie201712017.pd

Metalâ Chelated Polymer Nanodiscs for NMR Studies

Paramagnetic relaxation enhancement (PRE) is commonly used to speed up spin lattice relaxation time (T1) for rapid data acquisition in NMR structural studies. Consequently, there is significant interest in novel paramagnetic labels for enhanced NMR studies on biomolecules. Herein, we report the synthesis and characterization of a modified poly(styreneâ coâ maleic acid) polymer which forms nanodiscs while showing the ability to chelate metal ions. Cu2+â chelated nanodiscs are demonstrated to reduce the T1 of protons for both polymer and lipidâ nanodisc components. The chelated nanodiscs also decrease the proton T1 values for a waterâ soluble DNA Gâ quadruplex. These results suggest that polymer nanodiscs functionalized with paramagnetic tags can be used to speedâ up data acquisition from lipid bilayer samples and also to provide structural information from waterâ soluble biomolecules.Speeding up data acquisition: Design of a polymer nanodisc containing a DOTA chelator enables the utilization of the PRE effect in studies using lipid nanodiscs. This new technique can be applied to waterâ soluble biomolecules such as Gâ quadruplexes.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/152508/1/anie201910118.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/152508/2/anie201910118-sup-0001-misc_information.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/152508/3/anie201910118_am.pd

Metalâ Chelated Polymer Nanodiscs for NMR Studies

Paramagnetic relaxation enhancement (PRE) is commonly used to speed up spin lattice relaxation time (T1) for rapid data acquisition in NMR structural studies. Consequently, there is significant interest in novel paramagnetic labels for enhanced NMR studies on biomolecules. Herein, we report the synthesis and characterization of a modified poly(styreneâ coâ maleic acid) polymer which forms nanodiscs while showing the ability to chelate metal ions. Cu2+â chelated nanodiscs are demonstrated to reduce the T1 of protons for both polymer and lipidâ nanodisc components. The chelated nanodiscs also decrease the proton T1 values for a waterâ soluble DNA Gâ quadruplex. These results suggest that polymer nanodiscs functionalized with paramagnetic tags can be used to speedâ up data acquisition from lipid bilayer samples and also to provide structural information from waterâ soluble biomolecules.Speeding up data acquisition: Design of a polymer nanodisc containing a DOTA chelator enables the utilization of the PRE effect in studies using lipid nanodiscs. This new technique can be applied to waterâ soluble biomolecules such as Gâ quadruplexes.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/152508/1/anie201910118.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/152508/2/anie201910118-sup-0001-misc_information.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/152508/3/anie201910118_am.pd

Hydrophobic Functionalization of Polyacrylic Acid as a Versatile Platform for the Development of Polymer Lipid Nanodisks

Polymer nanodisks have shown great potential as membrane mimetics that enable the study of functional membrane protein structural biology and also have a wider application in other fields such as drug delivery. To achieve these research goals, the ability to have a cheap, simple, fully customizable platform for future nanodisks technology applications is paramount. Here, a facile functionalization of polyacrylic acid (PAA) with varying hydrophobic groups that form nanodisks at different sizes is successfully demonstrated. The study shows that the choice of hydrophobic group can have a noticeable effect on the polymer solubilization properties and polymer‐induced perturbation to the encased lipid bilayer. Due to this robust, tunable chemical synthesis method, PAA is an exciting platform for the future optimization of the hydrophobic, hydrophilic, or direct purposed functionalizations for polymer nanodisks.Functionalized polyacrylic acid polymers with varying hydrophobic groups form lipid nanodisks. Alkyl‐PAA polymer nanodisks are size tunable by simply varying the lipid:polymer ratio and macro–nanodisks exhibit magnetic alignment. The facile functionalization enables the investigation of the effect of the hydrophobic group of PAA on the nanodisk formation and lipid bilayer properties.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/148220/1/smll201804813_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/148220/2/smll201804813.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/148220/3/smll201804813-sup-0001-S1.pd

pH Tunable and Divalent Metal Ion Tolerant Polymer Lipid Nanodiscs

The development and applications of detergent-free membrane mimetics have been the focus for the high-resolution structural and functional studies on membrane proteins. The introduction of lipid nanodiscs has attracted new attention toward the structural biology of membrane proteins and also enabled biomedical applications. Lipid nanodiscs provide a native lipid bilayer environment similar to the cell membrane surrounded by a belt made up of proteins or peptides. Recent studies have shown that the hydrolyzed form of styrene maleic anhydride copolymer (SMA) has the ability to form lipid nanodiscs and has several advantages over protein or peptide based nanodiscs. SMA polymer lipid nanodiscs have become very important for structural biology and nanobiotechnological applications. However, applications of the presently available polymer nanodiscs are limited by their instability toward divalent metal ions and acidic conditions. To overcome the limitations of SMA nanodiscs and to broaden the potential applications of polymer nanodiscs, the present study investigates the tunability of SMA polymer nanodiscs by systematically modifying the maleic acid functional group. The two newly developed polymers and subsequent lipid nanodiscs were characterized using solid-state NMR, FT-IR, TEM, and DLS experiments. The pH dependence and metal ion stability of these nanodiscs were studied using static light scattering and FTIR. The reported polymer nanodiscs exhibit unique pH dependent stability based on the modified functional group and show a high tolerance toward divalent metal ions. We also show these tunable nanodiscs can be used to encapsulate and stabilize a polyphenolic natural product curcumin