Photostability of Hydroxocobalamin: Ultrafast Excited State Dynamics and Computational Studies

Abstract

Hydroxocobalamin is a potential biocompatible source of photogenerated hydroxyl radicals localized in time and space. The photogeneration of hydroxyl radicals is studied using time-resolved spectroscopy and theoretical simulations. Radicals are only generated for wavelengths <350 nm through a mechanism that involves competition between prompt dissociation and internal conversion. Characterization of the lowest-lying singlet potential energy surface provides insight into the photochemistry of hydroxocobalamin and other cobalamin compounds.

Visible Light‐Induced Radical Mediated DNA Damage

“…This result is supported by a recent report that ultraviolet light (<350 nm) is required for photoactivation of HOCbl . Kozlowski and coworkers have performed excellent research on photochemical production of by HOCbl .…”

“…This demonstrates that when visible light is employed DNA cleavage is mediated by ÁCH 3 in contrast to UV light-mediated DNA cleavage by MeCbl, which primarily occurs as a result ÁOH. This result is supported by a recent report that ultraviolet light (<350 nm) is required for photoactivation of HOCbl (31,32). Kozlowski and coworkers have performed excellent research on photochemical production of ÁOH by HOCbl (31,32).…”

“…This result is supported by a recent report that ultraviolet light (<350 nm) is required for photoactivation of HOCbl (31,32). Kozlowski and coworkers have performed excellent research on photochemical production of ÁOH by HOCbl (31,32). The results of femtosecond UV-visible transient absorption spectroscopy demonstrate that there at least three electronic states that result from photoexcitation (32).…”

“…Kozlowski and coworkers have performed excellent research on photochemical production of by HOCbl . The results of femtosecond UV‐visible transient absorption spectroscopy demonstrate that there at least three electronic states that result from photoexcitation . Longer light wavelengths populate the energy minimum corresponding to the pOH/d → σ * electronic state, which is primarily responsible for deactivation.…”

Off to the Races: Comparison of Excited State Dynamics in Vitamin B12 Derivatives Hydroxocobalamin and Aquocobalamin

“…12−15 In particular, excitation of HOCbl at wavelengths shorter than 300 nm results in cleavage of the C−O bond with the formation of radical species. 12 The production of OH radicals is potentially useful in a variety of research areas including DNA cleavage, the Fenton reaction, and photosensitive bioactive reagents. 14,15 In light of these applications, it is important to understand the photochemistry of both HOCbl and H 2 OCbl + .…”