Milli q gradient ultrapure water system

Oligonucleotide sequences shown in Table 1 were synthesized by RiboBio Co. Ltd. Transfer RNA (Ribonucleotide acid; transfer from bovine liver; R4752) was purchased from Sigma-Aldrich. RNA stock solutions were prepared by dissolving oligonucleotides directly in 20 mM Tris-HCl pH 7.0, 40 mM KCl, and annealing in a thermocycler (first heated at 90°C for 2 min, then cooled down slowly to room temperature). The cyanine dye CyT was synthesized according to Hamer and Fichen's methods (45 ,46 ), and its purity was assessed by mass spectrometry, elemental analysis and NMR (Supplementary Information Part 1). The TO dye was obtained from Sigma-Aldrich. Stock solutions for CyT and TO were prepared by dissolving CyT and TO in methanol and water, respectively. RNase T1 was purchased from Invitrogen. All other chemicals were of analytical reagent grade and used without further purification. Ultrapure water, prepared by Milli-Q Gradient ultrapure water system (Millipore), was used in all experiments.

This consists of a complex of low-concentration (up to 12%) saturated and unsaturated polyfunctional organic acids (maleic acid—6%, polyacrylic acid—5%, citric acid—7%, distilled water). To prepare the amino acid solution, the raw components were dissolved in the ultra-pure water (provided with Millipore Milli-Q gradient ultrapure water system) and this mixture was subjected to ultrasound stirring (Q55 Sonica 55 W) with an amplitude of 50% for 5 min.

All these oligonucleotides of [d(TGGGT)]₄ (TG3T), [d(TGGGGT)]₄ (TG4T), [d(TGGGGGT)]₄ (TG5T), [d(TGGGGGGT)]₄ (TG6T) and[d(TGGGGGGGGT)]₄ (TG8T) were purchased from Sangon Biotech Co., Ltd. (Shanghai, China) and purified by HPLC. Ultrapure water was prepared by a Milli-Q gradient ultrapure water system (Millipore, Molsheim, France).
The stock solution of 100 μM dimeric cyanine dyes was prepared by dissolving into DMSO and storing in the dark at room temperature. PBS buffer (10 mM KH₂PO₄-K₂HPO₄, 70 mM KCL, 1 mM EDTA, pH 7.4) was used to dissolve the oligonucleotides. The absorbance at 260 nm was used to determine the concentrations of oligonucleotides. All oligonucleotides were heated to 95 °C for 5 min, rapidly cooled to 4 °C and kept overnight at 4 °C. Their folding topologies were identified by circular dichroism (CD) before usage.
The measured samples were prepared by corresponding DNA stocking solutions into 100 μL PBS containing 5 μM dyes. The final volume was 700 μL after addition of PBS. The samples were incubated for 12 h in the dark at room temperature before measurements we taken.

All oligonucleotides (Table S1) were synthesized by Sangon Biotechnology (Shanghai, China) and purified by ultra-polyacrylamide gel electrophoresis (ULTRAPAGE) (purity 95%). Analytical grade DMSO, KH₂PO₄ K₂HPO₄ and ethylenediaminetetraacetic acid (EDTA) were purchased from Beijing Chem. Co. (China) and used without further purification. Ultrapure water prepared by Milli-Q Gradient ultrapure water system (Millipore) was used throughout the experiments. The solution of oligonucleotides were dissolved in 17 mM phosphate buffer solution (K₂HPO₄/KH₂PO₄, pH 7.40) and heated at 85 °C for 15 min, and then slowly cooled to room temperature. Methylazacalix[6]pyridine (MACP6) was synthesized according to the literature52 (link) and thepurity was proved by element analysis41 (link) MACP6 was dissolved in DMSO to obtain the stock solution. All the samples were prepared as shown above unless special instructions were given.

Phosphate buffer saline (PBS; pH 7.2–7.4) was supplied by Thermo Fisher Scientific (Wilmington, USA). GelRed nucleic acid stain was acquired from SenBeiJia Biological Technology Co., Ltd. (Nanjing, China). NHydroxysuccinimide (NHS) and N-(3-(dimethylamino) propyl)-N′-ethylcarbodiimide hydrochloride (EDC) were purchased from Alfa Aesar (Ward Hill, MA, USA). Chloroauric acid (HAuCl₄), sodium hydroxide (NaOH), FeCl₃·6H₂O, ethylene glycol (EG), tetraethylorthosilicate (TEOS), 3-aminopropyltriethoxysilane (APTES), and 28% ammonium hydroxide (NH₃·H₂O) were obtained from Sinopharm Chemical Reagent Co., (Shanghai, China). Dialysis membrane (3.5 kDa), sodium acetate (NaAC), sodium citrate (Na₃Cit), avidin (activity ≥ 12 U/mg), and all of the HPLC-purified oligonucleotides listed in Additional file 1: Table S1 were prepared and purified by Sangon Biotech Co., Ltd. (Shanghai, China). All of the reagents and chemicals used were of analytical reagent grade. Ultrapure water was prepared by a Millipore Milli-Q gradient ultrapure water system (Millipore, MA).

Ammonium molybdate tetrahydrate (H₂₄Mo₇N₆O₂₄·4H₂O) (99%), thioacetamide (TAA) (98%), sulfathiazole (STZ), sulfadimidine (SDD), sulfadiazine (SDZ), sulfamethoxazole (SMZ), sulfacetamide (ST), sulfachloropyridazine (SCD), N₄-phthalylsulfathiazole (PST), succinylsulfathiazole (SST), sodium hydrogen phosphate (Na₂HPO₄), sodium dihydrogen phosphate (NaH₂PO₄), methanol for HPLC (99.9%) and acetonitrile for HPLC (99.9%) were purchased from Sigma-Aldrich (St Louis, USA). Acetone, sodium hydroxide (NaOH) and hydrochloric acid (HCl) were purchased from Beijing Chemical Works (Beijing, China). Polyethylene glycol (PEG4000) was purchased from Merck (Germany). Ultrapure water (18.2 MΩ cm) was prepared using a Milli-Q Gradient ultrapure water system (Millipore, Milford, MA, USA).
The eight SAs were dissolved in a 0.1 mol l⁻¹ NaOH solution to prepare standard stock solutions of 2.0 mg ml⁻¹ for each SA, and these standard solutions were stored at 4°C and protected from light. The working solutions to be analysed were diluted with ultrapure water. The calibration standards of SAs were prepared with five levels of concentration in the range of 0.3 to 30 µg ml⁻¹.