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Taking snapshots of photosynthetic water oxidation using femtosecond X-ray diffraction and spectroscopy.

Kern J, Tran R, Alonso-Mori R, Koroidov S, Echols N, Hattne J, Ibrahim M, Gul S, Laksmono H, Sierra RG, Gildea RJ, Han G, Hellmich J, Lassalle-Kaiser B, Chatterjee R, Brewster AS, Stan CA, Glöckner C, Lampe A, DiFiore D, Milathianaki D, Fry AR, Seibert MM, Koglin JE, Gallo E, Uhlig J, Sokaras D, Weng TC, Zwart PH, Skinner DE, Bogan MJ, Messerschmidt M, Glatzel P, Williams GJ, Boutet S, Adams PD, Zouni A, Messinger J, Sauter NK, Bergmann U, Yano J, Yachandra VK - Nat Commun (2014)

Bottom Line: The spectra show that the initial O-O bond formation, coupled to Mn reduction, does not yet occur within 250 μs after the third flash.Diffraction data of all states studied exhibit an anomalous scattering signal from Mn but show no significant structural changes at the present resolution of 4.5 Å.This study represents the initial frames in a molecular movie of the structural changes during the catalytic reaction in photosystem II.

View Article: PubMed Central - PubMed

Affiliation: 1] Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA [2] LCLS, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.

ABSTRACT
The dioxygen we breathe is formed by light-induced oxidation of water in photosystem II. O2 formation takes place at a catalytic manganese cluster within milliseconds after the photosystem II reaction centre is excited by three single-turnover flashes. Here we present combined X-ray emission spectra and diffraction data of 2-flash (2F) and 3-flash (3F) photosystem II samples, and of a transient 3F' state (250 μs after the third flash), collected under functional conditions using an X-ray free electron laser. The spectra show that the initial O-O bond formation, coupled to Mn reduction, does not yet occur within 250 μs after the third flash. Diffraction data of all states studied exhibit an anomalous scattering signal from Mn but show no significant structural changes at the present resolution of 4.5 Å. This study represents the initial frames in a molecular movie of the structural changes during the catalytic reaction in photosystem II.

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Oxygen production by PSII A) Relative O2 yield per PSII as detected by MIMS as a function of flash number (measurement shown is for PS II solutions, flow rate 0.5 μl/min, frequency 4 Hz, light intensity was 7 μJ for each fiber). B) O2 yield measured by MIMS as a function of flash number from PS IIsolutions (black) and PS II microcrystals (red).
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Figure 2: Oxygen production by PSII A) Relative O2 yield per PSII as detected by MIMS as a function of flash number (measurement shown is for PS II solutions, flow rate 0.5 μl/min, frequency 4 Hz, light intensity was 7 μJ for each fiber). B) O2 yield measured by MIMS as a function of flash number from PS IIsolutions (black) and PS II microcrystals (red).

Mentions: O2 detection via membrane-inlet mass spectrometry (MIMS) was used for optimizing the conditions for S-state turnover in the capillary flow sample delivery system, using a facsimile of the flow/illumination set up employed at LCLS (see Methods). One of the most important factors in the illumination scheme is the required light intensity for efficient turnover through the Si state cycle. To low intensities can lead to only partial turnover of the samples, while too high intensities increase the miss parameter via light scattering along the capillary, and may also inactivate the sample. The optimal light intensity can be found by the quality of the O2 oscillation pattern, and also by the total O2 produced per PSII complex and flash number. The former method should normally be sufficient, but a small uncertainty remains if there can be a certain part of the sample that never sees any light, and thus does not contribute to the oscillation pattern. To address this question approach, the latter method needs to be employed (see Methods), which requires the absolute calibration of the MIMS signals. The amount of 0.73 O2/RC after 3 flashes shows that the light conditions used for illumination are optimal for saturating all PSII reaction centers in the sample (Fig. 2A). The O2 evolution patterns obtained from PS II solutions and PS II microcrystals (Fig. 2B) show light induced turnover of the catalytic cycle as expected. Analysis of the flash pattern indicates that the S3 state is the majority component (≧55%) in the samples given two visible-laser flashes (2F) with virtually no S0 state present. In contrast, the largest component in the 3F samples is the S0 state (≧40%). Therefore the difference between the 3F and 2F samples is dominated by the formation of the S0 state at the expense of the S3 state.


Taking snapshots of photosynthetic water oxidation using femtosecond X-ray diffraction and spectroscopy.

Kern J, Tran R, Alonso-Mori R, Koroidov S, Echols N, Hattne J, Ibrahim M, Gul S, Laksmono H, Sierra RG, Gildea RJ, Han G, Hellmich J, Lassalle-Kaiser B, Chatterjee R, Brewster AS, Stan CA, Glöckner C, Lampe A, DiFiore D, Milathianaki D, Fry AR, Seibert MM, Koglin JE, Gallo E, Uhlig J, Sokaras D, Weng TC, Zwart PH, Skinner DE, Bogan MJ, Messerschmidt M, Glatzel P, Williams GJ, Boutet S, Adams PD, Zouni A, Messinger J, Sauter NK, Bergmann U, Yano J, Yachandra VK - Nat Commun (2014)

Oxygen production by PSII A) Relative O2 yield per PSII as detected by MIMS as a function of flash number (measurement shown is for PS II solutions, flow rate 0.5 μl/min, frequency 4 Hz, light intensity was 7 μJ for each fiber). B) O2 yield measured by MIMS as a function of flash number from PS IIsolutions (black) and PS II microcrystals (red).
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Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4151126&req=5

Figure 2: Oxygen production by PSII A) Relative O2 yield per PSII as detected by MIMS as a function of flash number (measurement shown is for PS II solutions, flow rate 0.5 μl/min, frequency 4 Hz, light intensity was 7 μJ for each fiber). B) O2 yield measured by MIMS as a function of flash number from PS IIsolutions (black) and PS II microcrystals (red).
Mentions: O2 detection via membrane-inlet mass spectrometry (MIMS) was used for optimizing the conditions for S-state turnover in the capillary flow sample delivery system, using a facsimile of the flow/illumination set up employed at LCLS (see Methods). One of the most important factors in the illumination scheme is the required light intensity for efficient turnover through the Si state cycle. To low intensities can lead to only partial turnover of the samples, while too high intensities increase the miss parameter via light scattering along the capillary, and may also inactivate the sample. The optimal light intensity can be found by the quality of the O2 oscillation pattern, and also by the total O2 produced per PSII complex and flash number. The former method should normally be sufficient, but a small uncertainty remains if there can be a certain part of the sample that never sees any light, and thus does not contribute to the oscillation pattern. To address this question approach, the latter method needs to be employed (see Methods), which requires the absolute calibration of the MIMS signals. The amount of 0.73 O2/RC after 3 flashes shows that the light conditions used for illumination are optimal for saturating all PSII reaction centers in the sample (Fig. 2A). The O2 evolution patterns obtained from PS II solutions and PS II microcrystals (Fig. 2B) show light induced turnover of the catalytic cycle as expected. Analysis of the flash pattern indicates that the S3 state is the majority component (≧55%) in the samples given two visible-laser flashes (2F) with virtually no S0 state present. In contrast, the largest component in the 3F samples is the S0 state (≧40%). Therefore the difference between the 3F and 2F samples is dominated by the formation of the S0 state at the expense of the S3 state.

Bottom Line: The spectra show that the initial O-O bond formation, coupled to Mn reduction, does not yet occur within 250 μs after the third flash.Diffraction data of all states studied exhibit an anomalous scattering signal from Mn but show no significant structural changes at the present resolution of 4.5 Å.This study represents the initial frames in a molecular movie of the structural changes during the catalytic reaction in photosystem II.

View Article: PubMed Central - PubMed

Affiliation: 1] Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA [2] LCLS, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.

ABSTRACT
The dioxygen we breathe is formed by light-induced oxidation of water in photosystem II. O2 formation takes place at a catalytic manganese cluster within milliseconds after the photosystem II reaction centre is excited by three single-turnover flashes. Here we present combined X-ray emission spectra and diffraction data of 2-flash (2F) and 3-flash (3F) photosystem II samples, and of a transient 3F' state (250 μs after the third flash), collected under functional conditions using an X-ray free electron laser. The spectra show that the initial O-O bond formation, coupled to Mn reduction, does not yet occur within 250 μs after the third flash. Diffraction data of all states studied exhibit an anomalous scattering signal from Mn but show no significant structural changes at the present resolution of 4.5 Å. This study represents the initial frames in a molecular movie of the structural changes during the catalytic reaction in photosystem II.

Show MeSH
Related in: MedlinePlus