Pure dimethyl sulfoxide dmso

Raw polybenzimidazole powder (trade name Dapozol^® PBI, chemical structure (C₂₀H₁₂N₄)_n) was provided by Blue World Technologies ApS (Aalborg, Denmark). It had an average molecular weight of approximately 93,000 g mol⁻¹ and a density equal to 1.30 g cm^–3 at 23 °C. It was characterized by a wool-like texture and a yellowish-brown color.
Graphene oxide was purchased as a viscous aqueous dispersion (concentration of 4 mg mL⁻¹) from Graphenea, Inc. (Cambridge, MA, USA). The main properties were an average particle size of <10 µm, a monolayer content larger than 95%, and a pH of about 2.5.
Pure dimethyl sulfoxide (DMSO, chemical structure C₂H₆OS) was acquired from Sigma-Aldrich Corporation (St. Louis, MO, USA) in liquid form to be used as the solvent of the designed preparation procedure, described in Section 2.2. The same company also supplied pellets of sodium chloride (NaCl, ACS reagent, purity of ≥99.0%) and sodium hydroxide (NaOH, ACS reagent, purity of ≥97.0%).

ITC experiments were carried out at 25 ± 0.2 °C by a MicroCal PEAQ-ITC calorimeter. Arsenic binding flagellin variants in monomeric form were prepared in 100 mM 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) ((Sigma Aldrich), 150 mM NaCl, 1 mM Tris(2-carboxyethyl)phosphine hydrochloride (TCEP) (Sigma Aldrich) (pH 7.0). Before the measurement 10% v/v DMSO was added to the solution. As a titrant, phenylarsine oxide (PAO) (Sigma Aldrich) was first dissolved in pure dimethyl sulfoxide (DMSO) (Sigma Aldrich) to an appropriate concentration then diluted 10 times with 100 mM HEPES, 150 mM NaCl (pH 7.0) buffer containing 1 mM TCEP. A typical experiment consisted of a ~ 0.5 mM PAO solution titrated into a ~ 5 µM protein solution in the same buffer. Interaction between PAO and the buffer or the buffer and protein was checked by PAO-to-buffer and buffer-to-protein titrations, respectively. The ITC data were fitted to a one-binding-site model with the MicroCal PEAQ-ITC Analysis Software package provided by MicroCal, using non-linear least-squares algorithm.