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Single molecule
uorescence resonance energy transfer(FRET) and
small angle x-ray scattering(SAXS) experiment study quantitatively
the behavior of unfolded protein under native conditions in response
to the level of chemical denaturant. But predicts highly contradictory
answers. Most of the FRET studies suggest the signi?cant contrac-
tion of the unfolded dimension over the range of chemical denatu-
rant. In contradiction, SAXS studies fail to see the contraction of
unfolded domain under native condition. By considering the dynam-
ics of homopolymer, we calculate analytically the radius of gyration
of unfolded protein by taking the equilibrium limit. At high level of
chemical denaturant the hydrophobic interactions and intramolecular
hydrogen bonds in protein decrease in strength. We model the inter-
actions as a number cross-links of harmonic interactions with cut-o?.
The radius of gyration of the unfolded protein decreases monotoically
with increase in the interaction strength. Which corresponds to the
situation of collapse of denatured state proteins if we gradually de-
crease the concentration of chemical denaturant in FRET. Brownian
dynamics simulation agrees very well with the theoretical calculation
of radius of gyration. |