Chemicals and Reagents.
Phosphate-buffered saline (PBS) tablets, LC/MS grade water 0.1% formic
acid, methanol and acetonitrile 0.1% formic acid were from Fisher
Scientific (PA). Deuterium oxide (99.9%) was from Cambridge Isotope
Laboratories (MA). Urea and tris(carboxyethyl)phosphine (TCEP) were from
Sigma-Aldrich (MO). Reagent and sample vials for HDX-MS were from Trajan
Scientific and Medical (NC) and Thermo Scientific (CA), respectively.