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2.2.12. The radius of gyration of denatured proteins
Many proteins may denature completely, and RG values are reported in the
literature (Kohn et al. (2004) PNAS 101,12491–12496)35. Despite differences
in amino acid sequences, the plot below shows that almost all data fall on a
single straight line:
Figure 49
Note that the x-axis is the length (number of amino acid residues per chain),
not the molecular weight. However, each amino acid has (almost) the same
length along the peptide backbone. Hence, the length is roughly proportional
to M. In this case we find (by linear regression of log RG vs. length) an
exponent of 0.60. This value corresponds perfectly to a random coil in a good
solvent.
2.2.13. The wormlike chain model (WC)
We have previously in this chapter investigated
the stiffness parameter C∞, ‘the characteristic
35 The RG values were determined by X-ray scattering.