Grade 50 filter paper

N-hexane (≥95 %, PESTINORM®), acetone (Anala® NORMAPUR) and 2-propanol (Anala® NORMAPUR) were purchased as solvents from VWR Chemicals (Vienna, Austria). Ultra-pure water was obtained from a water purification system (Milli-Q gradient A 10, Milipore, Merck, Darmstadt, Germany). Norit® SAE SUPER (Cabot Norit Nederland B.V., Klazienaveen, The Netherlands) was used as activated carbon powder. Grade 50 filter paper was purchased from Whatman (GE Heathcare, Dassel, Germany). Copper wire (0.6 mm thickness) was from HSB Elektro (Uslar, Germany). DEHP (analytical standard) and DEHP-d4 (Pestanal®, analytical standard) were purchased from Merck (Darmstadt, Germany). DEHP and DEHP-d4 stock standards (each 5000 μg mL⁻¹) were prepared in 2-propanol. From these working standards of DEHP (50 μg mL⁻¹ and 500 μg mL⁻¹) and DEHP-d4 (50 μg mL⁻¹) were made in 2-propanol. All standards were stored at 4 °C in dark in amber brown glass vials closed with caps equipped with teflon septa. A 1 mM potassium chloride (KCl) solution was used as background solution to stabilise the ionic strength. PVC pellets were purchased from Industrie Generali spa (Samarate, Italy) and contained ∼35 % of DEHP. Each leaching or spiking experiment was conducted in triplicates, including three blanks.

After the GFP nanotrap step, purified b^0,+AT–rBAT samples were diluted to about 0.02 mg ml⁻¹ and applied onto glow-discharged copper grids coated with continuous carbon film. Staining was performed with three drops of 1% uranyl formate and blotting with Whatman Grade 50 filter paper. LAT1–CD98hc was prepared as described^{10 (link)} and stained similarly. Grids were imaged in a Tecnai BioTwin electron microscope operated at 120 kV. Roughly 50 images were recorded for each sample at a 49,000× magnification with a 2.2 Å nominal pixel size and analyzed in RELION 3.0^{55 (link)}.