Surprising Intrinsic Photostability of the Disulfide Bridge Common in Proteins

Anne Boutrup Stephansen, Rasmus Yding Brogaard, Thomas Scheby Kuhlman, Liv Bærenholdt Klein, Jørn Bolstad Christensen, Theis Ivan Sølling

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Abstract

For a molecule to survive evolution and to become a key building block in nature, photochemical stability is essential. The photolytically weak S–S bond does not immediately seem to possess that ability. We mapped the real-time motion of the two sulfur radicals that result from disulfide photolysis on the femtosecond time scale and found the reason for the existence of the S–S bridge as a natural building block in folded structures. The sulfur atoms will indeed move apart on the excited state but only to oscillate around the S–S center of mass. At long S–S distances, there is a strong coupling to the ground state, and the oscillatory motion enables the molecules to continuously revisit that particular region of the potential energy surface. When a structural feature such as a ring prevents the sulfur radicals from flying apart and thus assures a sufficient residence time in the active region of the potential energy surface, the electronic energy is converted into less harmful vibrational energy, thereby restoring the S–S bond in the ground state.
Original languageEnglish
JournalJournal of the American Chemical Society
Volume134
Issue number50
Pages (from-to)20279-20281
ISSN0002-7863
DOIs
Publication statusPublished - 2012

Bibliographical note

© 2012 American Chemical Society

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