Peaktrak software

Reversed-phase C-18 flash chromatography was performed using a Tekedyne Isco Combiflash^® RFx4 equipped with PeakTrak software (Version 2.1.19, Teledyne Isco, Lincoln, NE, USA). NMR data for 1 were collected on a JEOL ECA-600 spectrometer (JEOL USA, Peabody, MA, USA) operating at 600.17 MHz for ¹H, 150.9 MHz for ¹³C, and 60.8 MHz for ¹⁵N (instrument reference set to liquid NH₃). The edited-g-HSQC spectrum was optimized for 140 Hz, the g-HMBC spectrum was optimized for 8 Hz, and the band selective g-HMBC experiment was optimized for 8 Hz. Chemical shifts were referenced to solvent, e.g., DMSO-d₆ δ_H observed at 2.50 ppm and δ_C observed at 39.51 ppm. Chemical shifts for ¹⁵N were referenced to liquid NH₃ with long range J_H,N optimized for 6 Hz. NMR data for 2 were collected on a Bruker AMX 500 operating at 500 MHz for ¹H and 125 MHz for ¹³C (Bruker Biospin, Billerica, MA, USA). The HRMS spectrum was measured using a JEOL AccuTOF-DART 4G (JEOL USA, Peabody, MA, USA) using a prototype paper spray attachment. Isotope matching was used to confirm the presence of sulfur in the molecule (Figure S2). Calculated NMR spectra were generated using Advanced Chemical Development ChemPredictor Software (Version 11 Advanced Chemical Development, Toronto, ON, Canada).

Flash frozen tissues were lysed in Polysome Buffer (100 mM KCl, 5 mM MgCl₂, 10 mM Tris–HCl pH9.0, 1% Triton X–100 and 1% sodium deoxycholate in diethylpyrocarbonate—treated water) on ice using a polytron. Insoluble cell debris was pelleted by centrifugation at 2,500 X g for 15 min at 4°C. Cyclohexamide (0.1 mg/mL) and heparin (1 mg/mL) were added to the supernatant, and equal amounts of RNA (determined by A₂₆₀ using a Nanodrop Spectrophotometer) were loaded onto a 10–50% sucrose gradient (100 mM KCl, 5 mM MgCl₂, 10 mM Tris-HCl pH9.0). Sucrose gradients were subjected to ultracentrifugation (151,000 X g for 2 hours at 4°C) prior to fractionation using a density gradient fractionation system (Brandel). UV absorbance (A₂₅₄) was recorded using PeakTrak software (Teledyne Isco). Area under the curve (AUC) was calculated using Adobe Photoshop CS5.1 as described [89 ]. Individual peak/compartment areas were expressed relative to the total AUC of the profile.