The Sequential Unfolding of Ribonuclease A: Detection of a Fast Initial Phase in the Kinetics of Unfolding
AUTOR(ES)
Tsong, T. Y.
RESUMO
Temperature-jump studies have been used to detect a rapid reaction in the thermal unfolding of ribonuclease A (RNase A). The fast reaction occurs over a wide range of pH, and the results of a detailed study at pH 1.3 are reported here. Although its amplitude is small, the reaction is easily measurable over the entire temperature range of thermal unfolding. It occurs in the millisecond time range, and is faster by 3-4 orders of magnitude than the slow unfolding reaction studied previously. Unfolding is measured here by the change in absorbance at 287 nm, which reflects the exposure to solvent of buried tyrosine groups. Since the fast reaction has a detectable amplitude only in the temperature range of unfolding, it apparently detects the presence of intermediate, partly-folded states. Previous equilibrium studies of the unfolding of RNase A in the pH range 1-2 have indicated that it is essentially a 2-state reaction, without detectable intermediates.
ACESSO AO ARTIGO
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