DOI: 10.15125/bath-01291
title: Dataset for "The effect of polymer end-group on the formation of Styrene – Maleic Acid Lipid Particles (SMALPs)"

description: Styrene-maleic acid (SMA) copolymers have recently become the focus of attention for their ability to extract membrane proteins from cell membranes together with their native lipid environment. However, the mechanism by which these copolymers interact with lipid membranes is not well understood, nor are the key aspects of polymer structure in facilitating membrane protein extraction. The purpose for obtaining this data was to assess the effects of the copolymer end group upon solution behaviour and nanodisc formation. This dataset contains characterisation data for SMA copolymers with equivalent molecular weights and compositions (GPC, FTIR, 1H and 13C NMR spectroscopy) but varied end groups, including deuterostyrene variants used for neutron scattering experiments. End group exchange was monitored by UV-vis and 1H DOSY NMR spectroscopy. Aggregation behaviours arising from aqueous copolymer solutions, including the effects of heat treatment, were studied by dynamic light scattering (DLS) and interfacial surface tension measurements in both air and dodecane. Small angle neutron scattering (SANS) studies were used to examine the structure of copolymer aggregates, as well as that of the nanodiscs formed upon the addition of lipids, to further discern mechanistic differences.
description: Data collection methods are described in full in the publication "The effect of polymer end-group on the formation of Styrene – Maleic Acid Lipid Particles (SMALPs)". Briefly, various copolymers between styrene and maleic anhydride were prepared by RAFT polymerisation, which, when using DDMAT, results in a relatively-large and hydrophobic SC12 end group (SMAnh-SC12). The end group was then exchanged to a CN (SMAnh-CN) through reaction with excess radical initiators. A commercial variant, SMA2000, synthesised by free-radical polymerisation was also used for comparison. All copolymers were then hydrolysed to the acid form (SMA) before workup and purification.
description: 1H and 13C NMR: 
Spectra were analysed using Mestrelab MNova 11.0 software where spectra were baseline corrected and line broadening used to allow accurate integration of peak area. 

GPC: 
Chromatograms were analysed in Agilent GPC/SEC software to extract Mn and PDI values.

UV-vis: 
The presence of the SC12 end group can be monitored by the peak at 310 nm in UV-vis spectra. To estimate the percentage end group conversion, resultant spectra were normalised by the styrenic absorbance peak at 260 nm, the concentration of which is unchanged by end group conversion. This can then be compared to the reference spectrum for a solution of SMA2000, which has no thiocarbonylthio (SC12) end groups.
description: FTIR: 
FTIR measurements were conducted on a Perkin Elmer ATR desktop spectrometer with solid-state polymer samples at room temperature. 

1H & 13C NMR: 
1H and 13C NMR spectra were recorded on an Agilent 500 MHz spectrometer at room temperature using d6-acetone (for anhydride species) or D2O (for acid species) as the solvent. 

GPC: 
GPC was conducted using an Agilent GPC 1260 Infinity chromatograph using two PLgel 5μM MIXED-D 30 cm x 7.5 mm columns with a guard column PLgel 5 μm MIXED Guard 50 x 7.5 mm. The column oven was maintained at 35 °C, with GPC-grade THF as the eluent at a flow rate of 1.00 mL/min and refractive index detection and polymer concentrations between 1.0 – 2.0 mg/mL. The system was calibrated against 12 narrow molecular weight polystyrene standards with a range of Mw from 1050 Da to 2650 kDa. 

DLS: 
DLS was conducted using a Malvern Zetasizer Nanoseries at theta = 173 degrees (backscattering) and wavelength = 633 nm. 

Pendant Drop Tensiometry: 
Tensiometry was conducted on a FTA 1000 contact angle/surface tension analyser and processed using FTA 32 surface tension image analysis software. Syringe needles were prepared by extensive washing before SMA polymers in PBS at variant concentrations were passed through these to produce a small hanging droplet which was imaged at a typical rate of 10 images per second for 10 seconds. In the case of dodecane to PBS measurements, the sample drop was suspended in a quartz cuvette of dodecane. 

SANS: 
SANS was performed at the ISIS Neutron and Muon Source (Rutherford Appleton Laboratory, Didcot, UK), on the Larmor and Zoom instruments (doi:10.5286/ISIS.E.RB1910182), using 1 mm quartz Hellma cells at 25 °C. Data were collected on Larmor using the standard configuration for rectangular quartz cuvettes. A wavelength band of 0.9 to 13.3 Å was used with apertures of 20x20 mm2 and 6x8 mm2 separated by a distance of 5.1 m. The sample to detector distance was 4.1 m with the detector consisting of 80, 600 mm long, position sensitive 8 mm diameter 3He tube detectors. Prior to experiments, samples were mounted in a temperature controlled multi-position sample changer.
Data were collected on the Zoom SANS instrument in the standard configuration for rectangular quartz cuvettes, with a multi-position temperature controlled sample changer. A wavelength band of 1.75 to 16.5 Å was used with apertures of 20x20 mm2 (A1) and 8x8 mm2 (A2). The source to sample distance was set to 4.0m, and the sample to detector distance was 4.0m.
Data were subsequently reduced using Mantid software and the varying solution contrasts simultaneously fit using the NIST SANS analysis package within IgorPro.