Terbium chloride

All L-amino acids, D-amino acids (except D-histidine), purines, Valine analogs, Terbium chloride (212903), Maltose (M5895), Sodium phosphate dibasic (S7907), o-phthaldialdehyde (P0657), N-acetyl cysteine (A7250), Sodium tetraborate decahydrate (B3545), HPLC grade methanol (34860), 1-Propanol (34871), Trifluoroacetic acid (302031) and Mutanolysin enzyme (M9901) were purchased from Sigma. 2-Propanol (29113-95) was obtained from Nacalai Tesque. D-histidine (sc-255057) was purchased from SantaCruz Biotechnology. Acetonitrile (1.00317) and HCl (1.00029) were purchased from Merck. Percoll (17089109) was purchased from GE Healthcare. Oxyrase for broth was purchased from Oxyrase Inc and Sigma (SAE0013). BBL polypeptone peptone (211910), Dehydrated cooked meat media (226730), Brain heart infusion broth (BHI, 237500) and Reinforced Clostridial medium (RCM, 218081) were purchased from BD. Fetal bovine serum (S1810) was obtained from iDNA Biotechnology.
C. novyi-NT was a gift from the Kinzler-Vogelstein lab in John Hopkins University, USA.

Chemicals. All the DNA samples were from Eurofins (Huntsville, AL, USA). Silver nitrate, terbium chloride and other metal salts were purchased from Sigma-Aldrich (St. Louis, MO, USA) at the highest available purity. Tris(hydroxymethyl)aminomethane (Tris), 2-(N-morpholino)ethanesulfonic acid (MES), and 2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid (HEPES) were from Mandel Scientific Inc. (Guelph, ON, Canada).
Fluorescence spectroscopy. All the Tb³⁺ luminescence spectra were collected using a Fluoromax 4 fluorometer by exciting at 290 nm. Unless otherwise indicated, the DNA concentration was 1 µM for all the experiments, and the Tb³⁺ concentration was 5 µM. The buffer has been optimized and most experiments were performed in HEPES buffer (pH 7.5).
CD spectroscopy. CD spectra were obtained using a J-715 spectropolarimeter (JASCO, Easton, MD, USA) at 25 °C. The final G7 concentrations was 1 µM. Each measurement was recorded between 320 to 220 nm at a scanning rate of 100 nm·min⁻¹ using a sealed 1-mm path length quartz cuvette. The spectra were collected with a response time of 1 s. The final spectra were the averages of ten measurements. The cell holding chamber was flushed with a constant stream of dry nitrogen gas to avoid water condensation on the cell exterior.