Milli q purification unit

Analytical standard genistein is purchased from Sigma-Aldrich (U.S.). HPLC grade Formic acid, Acetonitrile, Ethanol, Methanol, and Dimethyl Sulphoxide (DMSO) were procured from Merck (Darmstadt, Germany). Milli-Q water was generated using a Milli-Q purification unit (Millipore, Bangalore, India) and used throughout the study.

Methanol and 2-propanol, both LC–MS grade, the ion pair reagents 3-TBA and TEA-acetic acid, media and sample preparation chemicals as well as all commercial standards (Tables SI and SIII) at the highest available purity were purchased from Sigma-Aldrich (Switzerland), unless stated otherwise. Nanopure water was obtained with an electric resistance of greater than 10 MΩ from a MilliQ purification unit (Millipore, Bedford, MA). TDP-rhamnose was synthesized upon request by CarboSynth (United Kingdom). All studies are in compliance with local ethical rules.

Guanidinium chloride (GdmCl), LiCl, KCl, KSCN, KI, and l-alanyl-l-alanine (2Ala) were used without further purification. Solutions for DRS and NMR experiments were prepared using H₂O with a specific resistivity >18 MΩcm⁻¹ from a Millipore MILLI-Q purification unit or using D₂O for infrared experiments. All samples were prepared by weighing the appropriate amount of salt and peptide into a 1 mL volumetric flask using an analytical balance. The peptide concentration was kept constant at 250 mM for all samples, while the salt concentration was varied from 0.05 M to 1.05 M for DRS and NMR experiments. For infrared experiments, we used salts concentrations of 1.05, 3, and 5 M.
For DRS experiments, 1 mL of each sample was brought in contact with the coaxial probes. For NMR experiments, 0.5 mL of the samples were placed in an NMR tube together with a capillary filled with DMSO-d6 for referencing. For all infrared experiments, solutions were contained between two CaF₂ windows (2 mm thickness, 2.54 cm diameter) separated by a 25 µm Teflon spacer. The infrared absorption spectra were measured right before collecting the 2D-IR data.