 | Figure 2
Nature Structural Biology
9, 425 - 430 (2002)
Published online: 29 April 2002; | doi:10.1038/nsb798
Designing a 20-residue proteinJonathan W. Neidigh, R. Matthew Fesinmeyer
& Niels H. Andersen | | | | Figure 2. Folding measures for Trp-cage construct 5b.
a, CD spectra of 66  M TC5b in pH 7 aqueous
buffer (2 °C) and buffer with 30% (v/v) TFE: residue molar ellipticity
versus wavelength. The curve shape suggests an unrealistically high
level of helicity from a reinforcing Trp side chain chromophore contribution
near the amide n− * transition. b,
CD-monitored melts for TC5b in pH 7 aqueous buffer with and without the
addition of 30% TFE or guanidine-HCl (6.3 M): [ ]222
versus T (°C). The denatured state data was fit to a line; the
curves through the other data points are polynomial fits with no theoretical
significance. c, Graphs illustrating the correlation of chemical shift
temperature gradients (  /T) with the chemical shift
deviations observed in D2O at 7 °C. All C H resonances
(|CSD| > 0.1 p.p.m.) are shown (solid squares) and are the
basis for the least-squares fit; other CH signals (open circles) in the
C-terminal portion of the structure fall on the same line. The Pro31-3
resonance (red circle) is an outlier (see text). d, Unfolded mole
fraction versus T (°C) from the CD data and NMR, the latter based on
11 fractional chemical shift deviations (23-, 26-, 30-2;
31- and - 3; 37-, -3 and -3; and 38-,
-2 and -3). The NMR measures are shown with error bars
( s.e.); greater scatter would be expected for noncooperative unfolding.
The CD values were converted to fraction unfolded assuming the guanidine-HCl
line in (b) represents 100% unfolded and a common temperature gradient
( []222 / T = +52° per °C) for the
100% folded baselines. The intercept values of []222 were
-16,100° (buffer) and -17,200° (30% TFE).
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