Polymer nanodiscs and macro-nanodiscs of a varying lipid composition

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1 Electronic Supplementary Material (ESI) for Chemical Communications. This journal is The Royal Society of Chemistry 2017 Polymer nanodiscs and macro-nanodiscs of a varying lipid composition Supporting Information Materials and Methods All lipids used in this study 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), 1,2- dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1-palmitoyl- 2-oleoylsn-glycero- 3-phospho(1-rac- glycerol) (POPG) were purchased from Avanti Lipids Polar, Inc. HEPES, phosphoric acid (H 3 PO 4 ), ytterbium chloride hexahydrate (YbCl 3 6H 2 O) were purchased from Sigma-Aldrich. SMA-EA copolymer synthesis and characterization were performed as recently reported from our group. 1 Nanodiscs formation and purification To prepare SMA-EA polymer macro-nanodiscs and investigate physicochemical properties of the bilayer, we first prepared multilamellar vesicles (MLVs) of different lipid compositions, involving saturated and unsaturated lipids with different main gel to liquid crystalline phase temperatures: POPC (T m = -4 C), DMPC (T m = +24 C), DPPC (T m = +41 C), DSPC (T m = +55 C). Desired aliquots of lipid stock solutions in chloroform were dried by using a stream of dry nitrogen gas and under high vacuum to complete dryness in a round-bottomed flask. The resulting lipid film was hydrated with an appropriate amount of HEPES buffer (10 mm buffer, ph 7.4) and dispersed by vigorous stirring in a water bath. Then, 20 mg of SMA-EA polymer dissolved in 10 mm HEPES buffer was added to was added to 20 mg of desired lipid components. Polymer nanodiscs formation can be followed (with naked eye) by observing the decreasing turbidity due to the solubilization of MLVs by the polymer. DMPC and DPPC MLVs spontaneously dissolved by the polymer to form nanodiscs at (or slightly above) room temperature, while POPC and DSPC required several freezethaw cycles from liquid nitrogen bath to a temperature above the lipid s main phase transition temperature. The resulting nanodiscs are reconcentrated into 200 µl volume for further experimental analysis. Once formed, regardless the lipid composition, the polymer based lipid nanodiscs exhibited high stability. Size of nanodsics was characterized by dynamic light scattering (DLS) experiments. Dynamic light scattering (DLS): Wyatt Technology DynaPro NanoStar with a 1 μl quartz MicroCuvette was used to perform all Dynamic Light Scattering (DLS) experiments. Solid-state NMR: 31 P, 14 N and 2D 13 C/ 1 H- 13 C SLF (separated-local-field) 2-5 NMR experiments were acquired using an Agilent/Varian 400 MHz solid-state NMR spectrometer with a 4-mm triple-resonance MAS probe. The resonance frequencies of 1 H, 31 P, 13 C and 14 N nuclei were , , and MHz, respectively. All NMR experiments were performed under static conditions. One-dimensional 1

2 1 H decoupled 31 P NMR spectra of flipped macro-nanodiscs (prepared by the addition of 0.5, 0.8, 1, 1.5 or 2 mm of YbCl 3 salt to macro-nanodiscs) were acquired using the following parameters: 5 μs 90 pulse, 30 khz continuous wave 1 H decoupling, 64 scans, and a 4s recycle delay. Onedimensional 14 N NMR spectra were recorded using the quadrupole-echo pulse sequence 6, 7 with a 90 pulse length of 4.5 μs and an echo-delay of 1.2 ms. 14 N magnetization was acquired using 30 ms acquisition time, 4000 scans and a recycle delay of 1.5 s with no 1 H decoupling. Two-dimensional 13 C/ 1 H- 13 C SLF experiments were performed on DMPC:SMA-EA and DPPC:SMA-EA polymer macro-nanodiscs in their respective fluid lamellar phase temperatures. The following experimental parameters were used for the 2D SLF experiments: 5 μs 90 0 pulse, 8 μs 180 pulse, 50 khz RF field strength for the BLEW-48 8 pulse sequence to suppress 1 H- 1 H homonuclear dipolar couplings during the t 1 period, 128 t 1 increments, 40 khz 1 H SPINAL-64 9 decoupling of protons during the acquisition of 13 C signal, 128 scans, and a 4s recycle delay. Figure S1: DLS profiles (Intensity %) of macro-nanodiscs of different lipids reconstituted in SMA- EA polymer nanodiscs. 2

3 Figure S2: 31 P solid-state NMR spectra of 7:3 POPC:POPG reconstituted in SMA-EA polymer nanodisc at the indicated ratio of lipid:polymer (w/w). These spectra show the solubilization of POPC: POPG MLVs to form nanodiscs with the addition of SMA-EA polymer. 3

4 Figure S3: 31 P solid-state NMR spectra of DMPC: SMA-EA macro-nanodiscs with 1:1 (w/w) lipid:polymer ratio obtained at different concentrations of YbCl 3 salt. The bilayer normal changed from the perpendicular (to the magnetic field) direction towards the parallel orientation with the increasing concentration of YbCl 3. Phosphorus-31 NMR spectra of aligned macro-nanodiscs: A static 31 P NMR spectrum of multilamellar vesicles (MLVs) of DMPC (or POPC) lipids spans from ~-15 ppm to ~30 ppm; therefore, the total span of the axially symmetric 31 P chemical shift anisotropy (CSA) powder pattern is ~45 ppm as reported in the literature 10, which depends on a number of factors including the level of hydration, ions and temperature. Importantly, this CSA span also vary with the extent of motion in the sample. For example, the 31 P CSA span observed for LUVs depends on the size of the vesicle 10 ; it was shown that the 31 P CSA span varies from ~45 ppm for 1000 nm (diameter) LUVs to ~27 ppm for 100 nm). Since the size of macro-nanodiscs are much smaller than that of MLVs or large LUVs (1000 nm), the 31 P CSA span for macro-nanodiscs should be smaller than that observed for 1000 nm LUVs); for example, the CSA span for bicelles 4

5 are small. In addition, there are other factors that could influence the 31 P CSA parameters for the nanodiscs investigated in this study: (a) the interaction of Yb 3+ ions with the lipid head group and (b) the shape of the nanodiscs that is different from the spherical shape of an LUV. Therefore, the motionally-averaged 31 P CSA for nanodiscs should be smaller than ~45 ppm. So, if one assumes a motionally-averaged 31 P CSA span of ~38 ppm for macro-nanodiscs, then the values can be expected to be ppm (for the parallel orientation) and ppm (for the perpendicular orientation). Since the isotropic 31 P chemical shift value is -2.9 ppm (relative to 31 P chemical shift of 100% phosphoric acid at 0 ppm) for the nanodiscs reported in this study, the above-mentioned values would become ppm (for the parallel orientation) and ppm (for the perpendicular orientation). The observed values for the nanodiscs are +20 ppm and ppm. These values (+20 to ppm, with an experimental error of 0.5 ppm) are close to the expected values (+22.4 to ppm); while the difference between these values may be attributed to the effect of Yb 3+ ions on the CSA, a systematic study to evaluate this effect could be useful; a detailed study on the interaction of Yb +3 ions with lipids can be found in a recently published paper. 11 Figure S4: 14 N solid-state NMR spectra of DMPC:SMA-EA macro-nanodiscs with 1:1 (w/w) lipid:polymer ratio obtained at different concentrations of YbCl 3 salt. The bilayer normal changed from the perpendicular (to the magnetic field) direction towards the parallel orientation with the increasing concentration of YbCl 3. 5

6 Figure S5: (A) Molecular structure of DPPC, (B) 2D 13 C/ 1 H- 13 C PELF spectrum of DPPC:SMA-EA macro-nanodiscs recorded at 42 C, and (C) 1 H- 13 C dipolar coupling slices extracted for the indicated carbons of DPPC. 6

7 DMPC DPPC Carbon labels (D exp ) (khz) S CH S CD 12, 13 Carbon labels (D exp ) (khz) S CH γ β α g g g C C C C γ α g g C C alipha C C C C C C Table S1. Experimentally obtained 1 H- 13 C dipolar couplings and CH order parameters measured from SMA-EA polymer macro-nanodiscs containing DMPC or DPPC. The DMPC lipid acyl chain order parameters measured from vesicles reported in the literature compare reasonably well with our experimentally measured order parameters. 7

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