6 methyl 2 thiouracil

The analytical standards 2-thiouracil (TU), 6-dimethyl-thiouracil, 6-ethyl-thiouracil, 6-methyl-2-thiouracil, 6-propyl-2-thiouracil, and 6-phenyl-thiouracil were purchased from Sigma-Aldrich (St. Louis, MO, USA), whereas the deuterated internal standard 6-propyl-2-thiouracil-d₅ (PTU-d₅) was from Toronto Research Chemicals (Toronto, Canada). Stock (1 mg mL^-1) and working solutions (1 and 0.1 ng μL^-1) were prepared in methanol and stored in dark glass bottles at -20°C.
Reagents were of analytical grade when used for extraction purposes and of LC-MS grade for UHPLC-MS applications. They were respectively purchased from VWR International (Merck, Darmstadt, Germany) and Fisher Scientific (Loughborough, UK). Ethylenediaminetetraacetic acid (EDTA) was from VWR International (Merck, Darmstadt, Germany) and hydrogen chloride from Sigma-Aldrich (St. Louis, MO, USA). Phosphate buffer was adjusted to a pH of 7 and saturated with 1% of DL-dithiothreitol (DTT) (Sigma-Aldrich, St. Louis, MO, USA). Ultrapure water (0.055 μS cm^-1) was obtained by means of a purified-water system (Sartorius AG, Göttingen, Germany).

The compounds 2-thiouracil, 6-methyl-2-thiouracil, 2,2′-bipyridine, and copper(II) chloride employed in the complex syntheses were purchased from Sigma Aldrich (St. Louis, MO, USA). Solvents (grade PA) were commercially obtained and used without further purification. CHN elemental analyses were performed using a Perkin-Elmer 2400 Analyzer (Perkin-Elmer, Waltham, MA, USA). FT-IR spectra were obtained by a JASCO-4100 spectrophotometer (Jasco, Easton, MD, USA) in the spectral window of 4000–400 cm⁻¹, using sample dispersion in KBr. Melting point values were determined on a DF-3600 Instruterm apparatus (Instruterm, São Paulo, SP, Brazil). UV-Vis analyses were performed in the same biological experimental conditions on double beam PerkinElmer Spectrophotometer Lambda 650S using quartz cuvettes of 1 cm optical path. HRMS was performed on a Bruker Mass Spectrometer IES-Q-QTOF-micro TOF III (Bruker Daltonics) in the positive mode (m/z 120–1200), quadrupole Ion energy 5.0 eV and cell collision energy of 10 eV. The samples were prepared using 0.0001 g/mL (water) and 0.1% of formic acid.