Stanford Univ., CA (United States). Dept. of Chemistry; SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL); Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory
SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL)
Stanford Univ., CA (United States). Dept. of Chemistry; SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL)
In-situ inventory of sulfurous products from the sulfur K-edge synchrotron X-radiolysis of L-cysteine, in solid-phase and anaerobic (pH 5) and air-saturated (pH 5, pH 7, and pH 9) solutions without and with 40% glycerol is reported. Sequential K-edge X-ray Absorption Spectroscopic (XAS) spectra were acquired. L-cysteine degraded systematically in the X-ray beam. Radiolytic products were inventoried by fits using the XAS spectra of sulfur model compounds. Solid L-cysteine declined to 92% fraction after a single K-edge XAS scan. After six scans 60 % remained, accompanied by 14 % cystine, 16 % thioether, 5.4 % of elemental sulfur, and smaller fractions of more highly oxidized products. In air-saturated pH 5 solution, 73 % of L-cysteine remained after ten scans, with 2 % cystine and 19 % elemental sulfur. Oxidation increased with 40% glycerol, yielding 67 %, 5 % and 23 % fractions, respectively, after ten-scans. Higher pH solutions exhibited less radiolytic chemistry. All the reactivity followed first-order kinetics. The anaerobic experiment displayed two reaction phases, with sharp changes in kinetics and radiolytic chemistry. Unexpectedly, the radiolytic oxidation of L-cysteine was increased in anaerobic solution. After ten-scans only 60% of the L-cysteine remained, along with 17 % cystine, 22 % elemental sulfur, and traces of more highly oxidized products. A new aerobic reaction cycle is hypothesized, wherein dissolved dioxygen captures radiolytic H• or e$$-\atop{aq}$$, enters HO2•/O2•-, reductively quenches cysteine thiyl radical, and cycles back to O2. This cycle is suggested to suppress the radiolytic production of cystine in aerobic solution.
Frank, Patrick, et al. "Synchrotron X-radiolysis of <scp>l</scp> -cysteine at the sulfur K-edge: Sulfurous products, experimental surprises, and dioxygen as an oxidoreductant." Journal of Chemical Physics, vol. 150, no. 10, Mar. 2019. https://doi.org/10.1063/1.5079419
Frank, Patrick, Sarangi, Ritimukta, Hedman, Britt, & Hodgson, Keith O. (2019). Synchrotron X-radiolysis of <scp>l</scp> -cysteine at the sulfur K-edge: Sulfurous products, experimental surprises, and dioxygen as an oxidoreductant. Journal of Chemical Physics, 150(10). https://doi.org/10.1063/1.5079419
Frank, Patrick, Sarangi, Ritimukta, Hedman, Britt, et al., "Synchrotron X-radiolysis of <scp>l</scp> -cysteine at the sulfur K-edge: Sulfurous products, experimental surprises, and dioxygen as an oxidoreductant," Journal of Chemical Physics 150, no. 10 (2019), https://doi.org/10.1063/1.5079419
@article{osti_1499007,
author = {Frank, Patrick and Sarangi, Ritimukta and Hedman, Britt and Hodgson, Keith O.},
title = {Synchrotron X-radiolysis of <scp>l</scp> -cysteine at the sulfur K-edge: Sulfurous products, experimental surprises, and dioxygen as an oxidoreductant},
annote = {In-situ inventory of sulfurous products from the sulfur K-edge synchrotron X-radiolysis of L-cysteine, in solid-phase and anaerobic (pH 5) and air-saturated (pH 5, pH 7, and pH 9) solutions without and with 40% glycerol is reported. Sequential K-edge X-ray Absorption Spectroscopic (XAS) spectra were acquired. L-cysteine degraded systematically in the X-ray beam. Radiolytic products were inventoried by fits using the XAS spectra of sulfur model compounds. Solid L-cysteine declined to 92% fraction after a single K-edge XAS scan. After six scans 60 % remained, accompanied by 14 % cystine, 16 % thioether, 5.4 % of elemental sulfur, and smaller fractions of more highly oxidized products. In air-saturated pH 5 solution, 73 % of L-cysteine remained after ten scans, with 2 % cystine and 19 % elemental sulfur. Oxidation increased with 40% glycerol, yielding 67 %, 5 % and 23 % fractions, respectively, after ten-scans. Higher pH solutions exhibited less radiolytic chemistry. All the reactivity followed first-order kinetics. The anaerobic experiment displayed two reaction phases, with sharp changes in kinetics and radiolytic chemistry. Unexpectedly, the radiolytic oxidation of L-cysteine was increased in anaerobic solution. After ten-scans only 60% of the L-cysteine remained, along with 17 % cystine, 22 % elemental sulfur, and traces of more highly oxidized products. A new aerobic reaction cycle is hypothesized, wherein dissolved dioxygen captures radiolytic H• or e$-\atop{aq}$, enters HO2•/O2•-, reductively quenches cysteine thiyl radical, and cycles back to O2. This cycle is suggested to suppress the radiolytic production of cystine in aerobic solution.},
doi = {10.1063/1.5079419},
url = {https://www.osti.gov/biblio/1499007},
journal = {Journal of Chemical Physics},
issn = {ISSN 0021-9606},
number = {10},
volume = {150},
place = {United States},
publisher = {American Institute of Physics (AIP)},
year = {2019},
month = {03}}
SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL)
Sponsoring Organization:
USDOE Office of Science (SC); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23); National Institutes of Health (NIH)
Grant/Contract Number:
AC02-76SF00515
OSTI ID:
1499007
Journal Information:
Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 10 Vol. 150; ISSN 0021-9606
Hedman, Britt; Frank, Patrick; Penner-Hahn, James E.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 246, Issue 1-3https://doi.org/10.1016/0168-9002(86)90196-8
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