Development of an experimental apparatus to observe ultrafast phenomena by tender X-ray absorption spectroscopy at PAL-XFEL

Kim, Yujin; Nam, Daewoong; Ma, Rory; Kim, Sunam; Kim, Myung Jin; Kim, Jin Hong; Eom, Intae; Lee, Jae Hyuk; Kim, Tae Kyu

doi:10.1107/s1600577521011449

Cited by 5 publications

(2 citation statements)

References 48 publications

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“…The setup has been described in detail elsewhere. [57][58][59] Briefly, the sample was excited with the third harmonic (267 nm) of a Ti:Sa amplified laser system at 60 Hz repetition rate and 100 fs pulse duration (FWHM) of the UV pulses. The round laser focus diameter was 145 µm (1/e 2 ).…”

Section: Methodsmentioning

confidence: 99%

UV photochemistry of the L-cystine disulfide bridge in aqueous solution investigated by femtosecond X-ray absorption spectroscopy

Ochmann,

Harich,

et al. 2024

Preprint

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Despite the biological relevance of the disulfide bond as the motive, which stabilizes the tertiary structure of many proteins, its photostability, UV-induced bond cleavage mechanisms and secondary photochemistry are still contested after decades of research. In this study, we employed femtosecond X-ray absorption spectroscopy to unravel the photochemistry of the aliphatic disulfide bridge of the semi-essential proteinogenic amino acid L-cysteine (L-cystine) in aqueous solution. We observe homolytic bond cleavage upon UV irradiation and the emergence of thiyl radicals as the single primary photoproduct and its ultrafast decay due to geminate recombination at remarkably high quantum yield in excess of 80% within 20 ps. These dynamics coincide with the emergence of a secondary product, attributed to the perthiyl radical. More than 70% of broken disulfide bridges form within the first nanosecond after bond cleavage. From these observations, we establish a dynamic photostability of the disulfide bridge and a mechanism of perthiyl radical formation from a 'hot' ground-state parent molecule that asymmetrically fragments along a carbon-sulfur bond, resolving long-standing questions in the photochemistry of disulfide bridges in condensed phase.

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Section: Methodsmentioning

confidence: 99%

UV photochemistry of the L-cystine disulfide bridge in aqueous solution investigated by femtosecond X-ray absorption spectroscopy

Ochmann,

Harich,

et al. 2024

Preprint

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show abstract

“…Typically, the TR x-ray scattering experiments are performed at X-ray Scattering and Spectroscopy (XSS) and Nano Crystallography and coherent Imaging (NCI) instruments. Additionally, the PAL-XFEL has the capability to deliver tender x-rays and self-seeded beams with the highest brightness in the world, 108,109 although these experimental conditions are not widely employed for TR x-ray scattering.…”

Section: X-ray and Electron Sources For Time-resolved Experimentsmentioning

confidence: 99%

A comparative review of time-resolved x-ray and electron scattering to probe structural dynamics

Lee,

Oang,

Kim

et al. 2024

Structural Dynamics

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The structure of molecules, particularly the dynamic changes in structure, plays an essential role in understanding physical and chemical phenomena. Time-resolved (TR) scattering techniques serve as crucial experimental tools for studying structural dynamics, offering direct sensitivity to molecular structures through scattering signals. Over the past decade, the advent of x-ray free-electron lasers (XFELs) and mega-electron-volt ultrafast electron diffraction (MeV-UED) facilities has ushered TR scattering experiments into a new era, garnering significant attention. In this review, we delve into the basic principles of TR scattering experiments, especially focusing on those that employ x-rays and electrons. We highlight the variations in experimental conditions when employing x-rays vs electrons and discuss their complementarity. Additionally, cutting-edge XFELs and MeV-UED facilities for TR x-ray and electron scattering experiments and the experiments performed at those facilities are reviewed. As new facilities are constructed and existing ones undergo upgrades, the landscape for TR x-ray and electron scattering experiments is poised for further expansion. Through this review, we aim to facilitate the effective utilization of these emerging opportunities, assisting researchers in delving deeper into the intricate dynamics of molecular structures.

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UV photochemistry of the L-cystine disulfide bridge in aqueous solution investigated by femtosecond X-ray absorption spectroscopy

Ochmann,

Harich,

et al. 2024

Nat Commun

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The photolysis of disulfide bonds is implicated in denaturation of proteins exposed to ultraviolet light. Despite this biological relevance in stabilizing the structure of many proteins, the mechanisms of disulfide photolysis are still contested after decades of research. Herein, we report new insight into the photochemistry of L-cystine in aqueous solution by femtosecond X-ray absorption spectroscopy at the sulfur K-edge. We observe homolytic bond cleavage upon ultraviolet irradiation and the formation of thiyl radicals as the single primary photoproduct. Ultrafast thiyl decay due to geminate recombination proceeds at a quantum yield of >80 % within 20 ps. These dynamics coincide with the emergence of a secondary product, attributed to the generation of perthiyl radicals. From these findings, we suggest a mechanism of perthiyl radical generation from a vibrationally excited parent molecule that asymmetrically fragments along a carbon-sulfur bond. Our results point toward a dynamic photostability of the disulfide bridge in condensed-phase.

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Development of an experimental apparatus to observe ultrafast phenomena by tender X-ray absorption spectroscopy at PAL-XFEL

Cited by 5 publications

References 48 publications

UV photochemistry of the L-cystine disulfide bridge in aqueous solution investigated by femtosecond X-ray absorption spectroscopy

UV photochemistry of the L-cystine disulfide bridge in aqueous solution investigated by femtosecond X-ray absorption spectroscopy

A comparative review of time-resolved x-ray and electron scattering to probe structural dynamics

UV photochemistry of the L-cystine disulfide bridge in aqueous solution investigated by femtosecond X-ray absorption spectroscopy

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