TY - JOUR
T1 - On the photostability of the disulfide bond
T2 - an electronic or a structural property?
AU - Stephansen, Anne Boutrup
AU - Larsen, Martin Alex Bjørn
AU - Klein, Liv Bærenholdt
AU - Sølling, Theis Ivan
N1 - Papers from the 11th International Conference on Femtochemistry (FEMTO11) that took place at The Technical University of Denmark (DTU), Copenhagen
PY - 2014/10/17
Y1 - 2014/10/17
N2 - Photostability is an essential property of molecular building blocks of nature. Disulfides are central in the structure determination of proteins, which is in striking contradiction to the result that the S-S bond is a photochemically labile structural entity that cleaves to form free radicals upon light exposure. In an earlier contribution we hypothesized that the key to the photostability of some disulfides may be found in a cyclic structural arrangement. Here we provide further evidence to support this hypothesis by showing that straight chain disulfides undergo ultrafast S-S dissociation on a sub 50 fs timescale without further ado. In a cyclic motif resembling the cysteine-disulfide bond in proteins, light can perturb the S-S bond to generate short-lived diradicaloid species, but the sulfur atoms are conformationally restricted by the ring that prevents the sulfur atoms from flying apart. Conversely, in a straight chain conformation, light perturbation results in two separated R S · radicals because there is no restoring force to counteract the repulsive motion of the sulfur atoms. For the cyclic conformation this restoring force is provided by the cyclic framework, and thus the photostability of disulfide-bonds must be ascribed a cyclic structural arrangement.
AB - Photostability is an essential property of molecular building blocks of nature. Disulfides are central in the structure determination of proteins, which is in striking contradiction to the result that the S-S bond is a photochemically labile structural entity that cleaves to form free radicals upon light exposure. In an earlier contribution we hypothesized that the key to the photostability of some disulfides may be found in a cyclic structural arrangement. Here we provide further evidence to support this hypothesis by showing that straight chain disulfides undergo ultrafast S-S dissociation on a sub 50 fs timescale without further ado. In a cyclic motif resembling the cysteine-disulfide bond in proteins, light can perturb the S-S bond to generate short-lived diradicaloid species, but the sulfur atoms are conformationally restricted by the ring that prevents the sulfur atoms from flying apart. Conversely, in a straight chain conformation, light perturbation results in two separated R S · radicals because there is no restoring force to counteract the repulsive motion of the sulfur atoms. For the cyclic conformation this restoring force is provided by the cyclic framework, and thus the photostability of disulfide-bonds must be ascribed a cyclic structural arrangement.
KW - CASSCF
KW - Disulfide
KW - Photodissociation
KW - Photostability
KW - Time-resolved mass spectrometry
U2 - 10.1016/j.chemphys.2014.02.005
DO - 10.1016/j.chemphys.2014.02.005
M3 - Journal article
AN - SCOPUS:84907887579
SN - 0301-0104
VL - 442
SP - 77
EP - 80
JO - Chemical Physics
JF - Chemical Physics
ER -