Thymine

Hydrogen peroxide, ferric sulfate, ferric chloride, catalase, the Hydrogen peroxide assay kit, and the phosphorothioate-modified dinucleotides dGsA and dGA were purchased from Sangon Biotech (Shanghai) Co., Ltd. Trimethoprim, thymine, α-(4-pyridyl-N-oxide)-N-tert-butylnitrone (POBN), diethylenetriaminepentaacetic acid (DTPA), Hanks’ Balanced Salt Solution (HBSS, without phenol red, calcium chloride and magnesium sulfate), threonine, NAD⁺ and Chelex-100 were purchased from Sigma. The DNeasy Tissue kit was purchased from QIAGEN. The Cycle-Pure Kit, Bacterial DNA Kit, and Gel Extraction Kit were purchased from OMEGA Bio-Tech. Luria-Bertani (LB) broth contained 10 g/L of BactoTryptone, 5 g/L yeast extract, and 10 g/L sodium chloride unless otherwise noted. The modified marine broth medium 2216E contained 5 g/L tryptone, 1 g/L yeast extract, 0.1 g/L FePO₄, and 34 g/L sodium chloride. K medium contained A salts, 0.2% glucose, 1 mM MgCl₂, 0.5 mM amino acids and 5 mg/L thiamine. The media were supplemented with the following concentrations of antibiotics (unless otherwise noted): ampicillin (Amp) 100 μg/ml and chloramphenicol (Cml) 12.5 μg/ml. Solid medium was supplemented with 1.5% (w/v) agar-A.

All chemicals were purchased and used without any further purification. To perform mercury ion quantification assay, mercury nitrate (99%, Guangzhou chemical reagent factory, Guangzhou, China) was dissolved in purified water to prepare aqueous solution with various concentrations. Thymine (Sigma-Aldrich Co., LLC., St. Louis, MO, USA) was dissolved in purified water to prepare solutions of 10⁻³ M. Cetyltrimethyl-ammonium bromide (CTAB, 99%), cadmium chloride (CdCl₂, 99%) obtained from Kermel (Tianjin, China), toluene (C₇H₈, A.R.), hydrochloric acid (37% HCl, A.R.), Ethanol (C₂H₅OH, A.R.), potassium nitrate (KNO₃, 99%), zinc nitrate hexahydrate (Zn(NO₃)₂·6H₂O, 99%), cobaltous nitrate gexahydrate (Co(NO₃)₂·6H₂O, 99%), copper nitrate hydrate (Cu(NO₃)₂·3H₂O, 99%) and iron nitrate nonahydrate (Fe(NO₃)₃·9H₂O, 99%) obtained from Guangzhou chemical reagent factory (Guangzhou, China). Hydrogen tetrachloroaurate (HAuCl₄ 3H₂O, 99.99%), sodium borohydride (NaBH₄, 99.99%), silver nitrate (AgNO₃, 99.99%) and ascorbic acid (AA, 98%) were purchased from Sigma-Aldrich (Sigma-Aldrich Co., LLC., St. Louis, MO, USA). Sodium nitrate (NaNO₃, 99%) was purchased from Damao chemical reagent company (Tianjin, China). Millipore water was used through all the experiments.

Adenine, thymine, sodium heparin (M_w 18 kDa), 1,9-dimethylmethylene blue and 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) were purchased from Sigma-Aldrich. Chemical vapor deposition grown single-walled carbon nano-tubes (CNTs) were supplied by Thomas Swan & Co. Ltd (Elicarb®). N-Hydroxysulfosuccinimide (sulfo-NHS) was purchased from Pierce Biotechnology Inc. (Rockford, IL). CyQuant Cell Proliferation Assay Kit, trypsin–EDTA solution, streptomycin and penicillin were purchased from Invitrogen Co. (Carlsbad, CA). Recombinant human BMP-2 (rhBMP-2) and the BMP-2 Quantikine ELISA Kit were obtained from R&D Systems (Minneapolis, USA). All other chemicals were used as received.

Adenine, thymine, cytosine, guanine, and uridine were purchased from Sigma-Aldrich (St. Louis, MO, USA). The purity of Adenine, thymine, cytosine, and uridine was ≥ 99%, whereas that of guanine was 98%. We did not perform further purification before the experiments.

Several monomers and polymers considered to be strong biosignatures of life (amino acids, nucleic acids and oligopeptides) were used at different stages of optimization, as they are distinct in terms of polarities, chemical structures and molecular masses, and such biomarkers were used to select generic trapping parameters.
A commercial mix of five oligopeptides (Sigma-Aldrich, Steinheim, Germany) contained a dipeptide (glycine-tyrosine (gly-tyr)), a tripeptide (valine-tyrosine-valine (val-tyr-val)) and three oligopeptides (leu-enkephalin, met-enkephalin and angiotensin II), each at 0.5 mg. Nucleic acids such as cytosine (>99%), uracil (>99%) and thymine (>99%) were purchased from Sigma-Aldrich. Amino acids (alanine, glycine, valine, leucine, isoleucine, proline, methionine, arginine, cysteine, threonine, serine, aspartic acid, glutamic acid, histidine, lysine, phenylalanine, tyrosine) and other oligopeptides were supplied by Sigma-Aldrich (St. Louis, MO, USA). LC mobile phases were prepared with HPLC grade acetonitrile and ultrapure grade formic acid, purchased from Sigma-Aldrich. Purified water was generated by a Purelab Flex purifier system (Veolia, Paris, France).