查看文章

Revised Manuscript Received August 30, 1994® abstract: The development of nonpolar surfaces during the folding of Escherichia coli dihydrofolate reductase (DHFR) was studied by monitoring the time-dependent fluorescence of 1-anilinonaphthalene-8-sulfonate (ANS) included in the refolding solution. Stopped-flow refolding experiments demonstrated a rapid increase in fluorescence intensity within the dead time of mixing (5 ms), indicating thatthe earliest detectable folding intermediate contains hydrophobic surfaces which are capable of binding ANS. A further increase in fluorescence intensity over the next 300 ms coincides with the formation of a set of four intermediates which are known to contain a specific tertiary contact [Kuwajima, K., Garvey, EP, Finn, BE, Matthews, C. R., & Sugai, S.(1991) Biochemistry 30, 7693-7703], Experiments performed in the presence of polar fluorescence quenchingagents …