Article Cite This: J. Phys. Chem. B 2019, 123, 6042−6048
pubs.acs.org/JPCB
Probing the Excited State of Methylcobalamin Using Polarized TimeResolved X‑ray Absorption Spectroscopy Lindsay B. Michocki,† Nicholas A. Miller,† Roberto Alonso-Mori,§ Alexander Britz,§ Aniruddha Deb,†,‡ James M. Glownia,§ April K. Kaneshiro,∥ Arkaprabha Konar,⊥ Jake Koralek,§ Joseph H. Meadows,† Danielle L. Sofferman,# Sanghoon Song,§ Megan J. Toda,∇ Tim B. van Driel,§ Pawel M. Kozlowski,∇ Kevin J. Kubarych,†,‡ James E. Penner-Hahn,†,‡ and Roseanne J. Sension*,†,‡,⊥ Downloaded via GUILFORD COLG on July 24, 2019 at 14:48:40 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.
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Department of Chemistry and ‡Biophysics, University of Michigan, 930 N University Avenue, Ann Arbor, Michigan 48109-1055, United States § Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States ∥ Department of Biological Chemistry, University of Michigan, 1150 W. Medical Center Dr., Ann Arbor, Michigan 48109-0600, United States ⊥ Department of Physics and #Program in Applied Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109-1040, United States ∇ Department of Chemistry, University of Louisville, 2320 South Brook Street, Louisville, Kentucky 40292, United States S Supporting Information *
ABSTRACT: We use picosecond time-resolved polarized Xray absorption near-edge structure (XANES) measurements to probe the structure of the long-lived photoexcited state of methylcobalamin (MeCbl) and the cob(II)alamin photoproduct formed following photoexcitation of adenosylcobalamin (AdoCbl, coenzyme B12). For MeCbl, we used 520 nm excitation and a time delay of 100 ps to avoid the formation of cob(II)alamin. We find only small spectral changes in the equatorial and axial directions, which we interpret as arising from small (
