Kinetic description of hydrogen-deuterium exchange in mixtures of H2O and D2O

Article (Faculty180)

cited authors

  • Hira, Arpona; Jin, Yining; Kim, Yong-Wa W; Zuiderweg, Erik R P; von Grafenstein, Hermann

description

  • <p>Hydrogen-deuterium exchange (HDX) provides valuable information about solvent accessibility of exchangeable hydrogens, and is used for studies of protein folding and conformational changes as well as ligand-receptor interactions. Current descriptions of HDX assume that exchange occurs in a large excess of DO or HO and account for either H-to-D or D-to-H exchange but neglect simultaneous exchange in the opposite direction. This study is aimed at removing this limitation, allowing both net H-to-D and D-to-H exchange to be studied at any level of deuterium in the exchange buffer. We present and experimentally test a mechanism-based model and two simpler mechanims-independent models of intrinsic bidirectional exchange as well as theoretical bidirectional models that include opening and closing of exchange-competent sites. All models of bidirectional intrinsic exchange and models of bidirectional EX1 and EX2 exchange can be represented by equations of the same form containing a single exponential term but different rate constants. Using simulated experimental data, we show that opening and closing rates can be extracted by model-based non-linear optimization and that this process is much more efficient, and in many scenarios only converges, when extended datasets acquired at different deuterium levels are used for optimization. We show that conventionally defined protection factors are not consistently informative about the open/closed state of exchange-competent sites. We suggest replacing protection factors with an assessment that is based on opening and closing rates extracted from experimental data using model-based non-linear optimization.</p>

authors

publication date

  • 2026

published in

start page

  • 107716

volume

  • 340