DOI: 10.15125/bath-01123
title: Dataset for "Fluorescent Styrene Maleic Acid Copolymers to Facilitate Membrane Protein Studies in Lipid Nanodiscs"

description: The purpose for obtaining this data was to characterise fluorescent styrene maleic acid copolymers synthesised via RAFT copolymerisation with styrene-analogous fluorophores. Copolymer behaviours were minimally affected and were able to spontaneously form lipid nanodiscs (SMALPs) upon incubation with DMPC vesicles. The potential usefulness of these novel copolymers to membrane protein (MP) research was also assessed. FRET was found to occur between the copolymer annulus and an encapsulated model MP, gramicidin, indicative of proximity. Further, aggregation caused quenching phenomena were used to monitor the transition from aggregated copolymer to nanodisc annulus during SMALP self assembly. Here, both the raw and processed data used in the publication are presented as .xls, .txt, and .pdf files, as indexed in the dataset.
description: Data collection methods are described in full in the publication "Fluorescent Styrene Maleic Acid Copolymers to Facilitate Membrane Protein Studies in Lipid Nanodiscs". 

Briefly, various copolymers were prepared by RAFT polymerisation. These were characterised by 1H NMR, 13C NMR, GPC and fluorescence spectroscopy. Subsequently the copolymers were introduced to DMPC vesicles, both with and without the model membrane protein, gramicidin (1.65% wt. SMA with 0.55% wt. DMPC [0.04% wt. gramicidin] in 50 mM PBS, 200 mM NaCl, pH=8.0). Here, turbid vesicle suspensions spontaneously cleared, indicating the successful formation of nanodiscs. Nanodiscs samples were characterised by DLS and SAXS, and their fluorescent behaviour captured through fluorescence spectroscopy.

RAFT Copolymerisation: 
Briefly, styrene, maleic anhydride, AIBN, DDMAT, and the appropriate fluorophore in the ratios indicated, were dissolved in 1,4-dioxane before oxygen was purged using nitrogen and three freeze-pump-thaw cycles. Reactions were heated to 60 oC for 24 hours and subsequently precipitated from diethyl ether, before drying. 

Hydrolysis of SMAnh to SMA:
Styrene maleic anhydride (SMAnh) was hydrolysed to styrene maleic acid (SMA) under basic reflux conditions. Typically, a 10% wt./vol. copolymer solution was prepared in 1 M NaOH (aq) and heated under reflux for 2 hours. The solution was then acidified to pH=3.0 using 4 M HCl, and centrifuged at 8000 rpm using an Eppendorf 5804R centrifuge for 15 minutes at 21 oC. The supernatant was removed and the copolymer pellet washed with ultrapure water and again recovered by centrifugation. The procedure was repeated a further three times. The pellet was then dissolved in 0.6 M NaOH before repeating the precipitation and washing procedure. The final precipitate was then dissolved in a minimal amount of 0.6 M NaOH and adjusted to pH=8.0 before freeze drying (Virtis SP Scientific) for a minimum of 24 hours.
description: 1H and 13C NMR:
Spectra were analysed using Mestrelab MNova 11.0 software where spectra were baseline corrected and line broadening routinely used to allow accurate integration of peak area. 

GPC:
Chromatograms were analysed in Agilent GPC/SEC software to extract Mn and PDI values. 

SAXS:
SAXS data were reduced using Foxtrot. The data were fit to parameters using a core shell bicelle model (combined with a cylindrical aggregate model where indicated) within SASview software.
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. 

SAXS:
SAXS data were collected in vacuo on a Xenocs NanoInXider instrument using a CuK(alpha) X-ray tube source with samples sealed in 1 mm borosilicate glass capillary tubes. 

Fluorometry:
All measurements were taken using an Agilent Cary Eclipse Fluorescence Spectrometer (slit width = 5 nm) with quartz cuvettes.
description: Details of the data and labelling is available in the README.txt file.