Studies of hydrogen exchange in proteins. II. The reversible thermal unfolding of chymotrypsinogen A as studied by exchange kinetics.

摘要: Abstract The hydrogen exchange kinetics of chymotrypsinogen A have been studied as a function temperature and pH. At low pH temperature, so chosen to assure that the proceeds predominantly through reversible thermal unfolding, experimental rate constants activation energy (72 ± 5 kcal at 2 27°) agree well with values calculated from available for unfolding refolding. higher temperatures below transition region, measured rates are energies lower (35 37°) than expected any process involving thermal, cooperative unfolding. It can be shown that, although formal mechanism changes becomes rate-limiting values, this fact does not explain energy. In order hard hydrogens without or changing nature such transition, we suggest existence considerable segmental motion relatively energies, exposing in kinetic sense all solution. Such pathway would sensitive part protein give us information about surface properties protein. As consequence, observed proteins general cannot easily correlated conformational thermodynamic sense.