Abstract：
:Synchrotron radiation circular dichroism, Fourier transform infrared, and nuclear magnetic resonance spectroscopies, and small-angle x-ray scattering were used to monitor the reversible thermal unfolding of hen egg white lysozyme. The results were compared with crystal structures and high- and low-temperature structures derived from molecular-dynamics calculations. The results of both experimental and computational methods indicate that the unfolding process starts with the loss of β-structures followed by the reversible loss of helix content from ∼40% at 20°C to 27% at 70°C and ∼20% at 77°C, beyond which unfolding becomes irreversible. Concomitantly there is a reversible increase in the radius of gyration of the protein from 15 Å to 18 Å. The reversible decrease in forward x-ray scattering demonstrates a lack of aggregation upon unfolding, suggesting the change is due to a larger dilation of hydration water than of bulk water. Molecular-dynamics simulations suggest a similar sequence of events and are in good agreement with the (1)H(N) chemical shift differences in nuclear magnetic resonance. This study demonstrates the power of complementary methods for elucidating unfolding/refolding processes and the nature of both the unfolded structure, for which there is no crystallographic data, and the partially unfolded forms of the protein that can lead to fibril formation and disease.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Meersman F,Atilgan C,Miles AJ,Bader R,Shang W,Matagne A,Wallace BA,Koch MHdoi
10.1016/j.bpj.2010.07.060subject
Has Abstractpub_date
2010-10-06 00:00:00pages
2255-63issue
7eissn
0006-3495issn
1542-0086pii
S0006-3495(10)00934-3journal_volume
99pub_type
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