Pulse labeling HDX NMR None P > 5 ATSTKKLHKEPATLIKAIDGDTVKLMYKGQPMTFRLLLVDTPETKHPKKGVEKYGPEASAFTKKMVENAKKIEVEFDKGQRTDKYGRGLAYIYADGKMVNEALVRQGLAKVAYVYKPNNTHEQLLRKSEAQAKKEKLNIWSEDNADSGQ

Refolding of deuterated H124L SNase was initiated at 15°C by a 1:2 dilution of the unfolded protein with a refolding buffer containing 150 mM KCl and 75 mM sodium acetate (pH 6.8) such that the final refolding mixture had a pH* of 5.3 and contained 100 mM KCl and 50 mM sodium acetate. Refolding was allowed to continue for a variable length of time.

Pulse labeling HDX NMR None 2.5 > P < 5 ATSTKKLHKEPATLIKAIDGDTVKLMYKGQPMTFRLLLVDTPETKHPKKGVEKYGPEASAFTKKMVENAKKIEVEFDKGQRTDKYGRGLAYIYADGKMVNEALVRQGLAKVAYVYKPNNTHEQLLRKSEAQAKKEKLNIWSEDNADSGQ

Refolding of deuterated H124L SNase was initiated at 15°C by a 1:2 dilution of the unfolded protein with a refolding buffer containing 150 mM KCl and 75 mM sodium acetate (pH 6.8) such that the final refolding mixture had a pH* of 5.3 and contained 100 mM KCl and 50 mM sodium acetate. Refolding was allowed to continue for a variable length of time.

Native exchange NMR None G(op)(kcal/mol)=~G(global unfolding) ATSTKKLHKEPATLIKAIDGDTVKLMYKGQPMTFRLLLVDTPETKHPKKGVEKYGPEASAFTKKMVENAKKIEVEFDKGQRTDKYGRGLAYIYADGKMVNEALVRQGLAKVAYVYKPNNTHEQLLRKSEAQAKKEKLNIWSEDNADSGQ

Samples for exchange studies were prepared by dissolving the lyophilized protein in an aqueous solution (natural isotopic abundance) containing 50 mM succinate-d4 to a final concentration of 3.0 mM. Samples of the nuclease H124L-Ca2+-pdTp ternary complex contained an additional 9.0 mM pdTp and 18 mM CaCl2. The pH was adjusted to 5.1, and the samples were lyophilized to dryness. Immediately prior to NMR data acquisition, the samples were redissolved in 100% D2O and placed into the Bruker AM500 NMR spectrometer.