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Putting the Disulfide Bridge at Risk: How UV‐C Radiation Leads to Ultrafast Rupture of the S‐S Bond
Author(s) -
Larsen Martin A. B.,
Skov Anders B.,
Clausen Christian M.,
Ruddock Jennifer,
Stankus Brian,
Weber Peter M.,
Sølling Theis I.
Publication year - 2018
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201800610
Subject(s) - excited state , chemistry , conical intersection , rydberg formula , photochemistry , excitation , population , molecular physics , atomic physics , chemical physics , ionization , physics , ion , demography , organic chemistry , quantum mechanics , sociology
We investigate the ultrafast photoinduced dynamics of the cyclic disulfide 1,2‐dithiane upon 200 nm excitation by time‐resolved photoelectron spectroscopy and show that the S−S bond breaks on an ultrafast time scale. This stands in stark contrast to excitation at longer wavelengths where the initially excited S 1 state evolves as the wavepacket is guided towards a conical intersection with S 0 by a torsional motion involving a partially broken bond between the sulfur atoms. This process at lower excitation energy allows for efficient (re‐)population of S 0 , rendering dithiane intact. At 200 nm, in contrast, the excitation leads to a manifold of higher excited states, S n , that are primarily of Rydberg character. We are able to follow the gradual transition from the initially excited state to the dissociative receiver state in real time. The Rydberg states are intersected by a repulsive valence state that mediates a transition to the repulsive S 2 surface. Therefore, we propose that the resulting diradical will eventually break apart on a longer timescale. The findings imply that upon going from UV−B to UV−C light the structural integrity of the disulfide moiety is compromised and proteins irradiated in this range will not be able to reform the initial tertiary structure, leading to loss of function.