Sodium chloride (nacl)

Basic medium (B medium) for Staphylococci consisted of Soy Peptone (10 g; Plato, Koblenz, Germany), Yeast Extract (5 g; Deutsche Hefewerke, Nuernberg, Germany), NaCl (5 g; Carl-Roth, Karlsruhe, Germany), Glucose (1 g; Carl Roth) and K₂HPO₄ (1 g; Applichem, Darmstadt, Germany). Deionized water was added to a final volume of 1 liter and pH was adjusted to 7.2.
LB medium for E. coli consisted of Peptone (10 g; Plato), Yeast Extract (5 g; Deutsche Hefewerke) and NaCl (5 g; Carl Roth). Deionized water was added to a final volume of 1 liter and pH was adjusted to 7.2. MacConkey agar was prepared according to the manufactures’ instructions (Carl Roth). Minimal media M9 for staphylococci consisted of Na₂HPO₄ (6 g; Carl Roth), KH₂PO₄ (3 g; Fisher Chemicals), NH₄Cl (1 g; Merck Darmstadt, Germany) and NaCl (0.5 g; Carl Roth). Deionized water was added to a final volume of 1 L, the media was autoclaved and supplemented with thiamine (2 µg/mL; Sigma Aldrich, Munich, Germany), MgSO₄ (1 mM; Carl Roth) and casamino acids (0.2%; BD Bioscience, Heidelberg, Germany). Cells were routinely grown at 37 °C either in liquid culture in baffled Erlenmeyer flasks (1:5 ratio) with shaking or on 1.5% agar plates.

Sodium iodide (>99.5%) was purchased
from Alfa Aesar. Sodium thiocyanate (99.99%), sodium tetraphenyl borate
(99.5%), and D₂O (>99.9%) were obtained from Sigma-Aldrich
for the HD-SFG measurements. For the TR-SFG experiments, D₂O (99.9%) was obtained by Eurisotop, and HCl (37%) was obtained from
VWR. Sodium perchlorate, anhydrous (>98%), was obtained from Thermo
Scientific. Sodium chloride (≥99.5%) and sodium sulfate (≥99%)
were purchased from Carl Roth GmbH. Sodium chloride was baked at 500
°C for 8 h before use. Other materials were used as received.
The DCl solution was prepared by mixing the HCl solution into D₂O. To avoid the oxidation of iodide ions and BPh₄^– ions, we
dissolved the Sodium iodide salt into D₂O under N₂ atmosphere and in a dark room just before SFG experiments.

The purified protein sample was estimated to be 90% pure, based on SDS-PAGE gels. Tris buffer, sodium cacodylate buffer, LB broth, kanamycin, isopropyl-ß-D-thiogalacto-pyranoside (IPTG), imidazole, sodium dodecylsulphate (SDS), NaCl, acrylamide/bisacrylamide solution 29:1, (30% w/v), N,N,N′,N′-tetramethylethylenediamine (TEMED), ammonium peroxide, Rotigarose His/Ni beads, methanol, glycerol, glycine, sodium chloride, powdered milk, and acetic acid were acquired from Carl Roth (Karlsruhe, Germany). Amonium-acetate buffer, ammonium persulphate (APS), β-mercaptoethanol, Tween 20, bromphenol blue, MOPS buffer, and diphenylamine (DPA) were acquired from Sigma-Aldrich (St. Louis, MO, USA). The Arg₂-2-naphthylamide (Arg-Arg–2NA) was produced by Bachem (Bubendorf, Switzerland); 2-naphthylamine (2-NA), 2-mercaptoethanol, and DNase I from bovine pancreas were produced by Merck (Darmstadt, Germany). For visualization of SDS-PAGE gels, we used PhastGel Blue R tablets (Pharmacia, Uppsala, Sweden). The EDTA was obtained from Kemika (Zagreb, Croatia), and metal (zinc, copper, cobalt, manganese) standard nitrate solutions were produced by Merck (Darmstadt, Germany).