Observations of C‐s and S‐s Bond Cleavage in the Photolysis of Disulfides in Solution

Abstract

A comparison of the transient absorption spectra from the photolysis of disulfides in solution suggests that C-S bond breakage is a common primary photolytic process. This process becomes more important as the resulting carbon centered radical is stabilized by increasing alkyl substitution or resonance interaction with an aromatic system. The perthiyl radical product is characterized by i,,, -380nm,r3,, -1700 M -' cm-' and decays by second order kinetics with k2 -3.7 x 10" M -' s -' in water.In the presence of 0,. the photolysis of disulfides which produce the thiyl radical give transient absorptions in the 5 W 0 0 nm region. Possible identities of these transients are discussed.

Reversible Intramolecular Hydrogen Transfer between Cysteine Thiyl Radicals and Glycine and Alanine in Model Peptides: Absolute Rate Constants Derived from Pulse Radiolysis and Laser Flash Photolysis

“…The photolytic cleavage of the cystine disulfide bond yields predominantly thiyl radicals 37. These thiyl radicals, (CysS • )Gly, will equilibrate with GlyC • through equilibrium 27.…”

The Photophysics and Photochemistry of the Near‐uv Absorbing Amino Acids‐iii. Cystine and Its Simple Derivatives

“…(RS') and perthiyl (RSS') radical products by flash photolysis. This has been partly achieved by Morine and Kuntz (1981) in a microsecond flash photolysis study of penicillamine disulfide ,18, cystine, cystamine ,19, and several alkyl disulfides. Perthiyl radicals, with A , , , = 380 nm (c = 1700 M-' cm-') in both water and cyclohexane, were observed directly after the flash.…”

Snm as a Photolabile Protecting Group for the Cysteinyl Radical − Direct Evidence from Time‐Resolved IR and UV/Vis Spectroscopies

“…[8,9] We assume that this absorption overlaps with the absorption of 1 at λ ϭ 345 nm, which has to be taken into account when evaluating the kinetic data. Within this time range, we did not observe the appearance of an absorption in the region of λ ഠ 400 nm indicating the formation of aminyl radical 6 by the loss of COS, a situation that is in accordance with the con- clusions from the TR-IR measurements.…”

“…According to published LFP data on cystine and its derivatives, the cysteinyl radical should exhibit an absorption maximum at 330 nm. [8,9] We assume that this absorption overlaps with the absorption of 1 at λ ϭ 345 nm, which has to be taken into account when evaluating the kinetic data. It has been reported in the literature that the cysteinyl radical can abstract sulfur atoms yielding the CysSS · radical with a transi-ent absorption at λ ഠ 380 nm.…”

“…It has been reported in the literature that the cysteinyl radical can abstract sulfur atoms yielding the CysSS · radical with a transi-ent absorption at λ ഠ 380 nm. [8,9] The formation of the CysSS · radical, however, is energetically not favoured. Thiyl radicals add quickly to double bonds in an anti-Markovnikov fashion.…”