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Updated: Aug 25, 2026

Single-molecule Manipulation of G-quadruplexes by Magnetic Tweezers
Published on: September 19, 2017
Formation of an alpha-helix in human tumor necrosis factor-alpha by guanidine hydrochloride-induced unfolding
Woojin Jeong1, Hang-Cheol Shin
1Department of Bioinformatics and Life Science, and Computer-Aided Molecular Design Research Center, Soongsil University, Seoul 156-743, Korea.
Abstract:
Human tumor necrosis factor-alpha (TNF-alpha) is a trimeric protein consisting primarily of beta-sheet. GdnHCl-induced unfolding of TNF-alpha was investigated at room temperature by circular dichroism (CD) and size exclusion chromatography. The secondary and tertiary structure of TNF-alpha persisted up to 0.9N GdnHCl regardless of incubation time, but, in the range of 1.2 N to 2.1 N GdnHCl, there was loss of tertiary structure accompanied by the formation of an alpha-helix, as revealed by far- and near-UV CD spectra. The structural changes occurred gradually in 1.2 and 2.1 N GdnHCl, but were rapid in 1.5 and 1.8 N GdnHCl. The GdnHCl-induced state of TNF-alpha is an unfolded, alpha-helical aggregate of about 130 monomers, as shown by size exclusion chromatography. We suggest the most likely pathway for the transition from beta-sheet to alpha-helix.
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