scholarly journals Photosynthetic reaction center variants made via genetic code expansion show Tyr at M210 tunes the initial electron transfer mechanism

2021 ◽  
Vol 118 (51) ◽  
pp. e2116439118
Author(s):  
Jared Bryce Weaver ◽  
Chi-Yun Lin ◽  
Kaitlyn M. Faries ◽  
Irimpan I. Mathews ◽  
Silvia Russi ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Free Energy ◽  
Amino Acid ◽  
Near Infrared ◽  
Transient Absorption ◽  
Global Analysis ◽  
Primary Electron ◽  
Transient Absorption Spectroscopy ◽  
Electron Transfer Mechanism ◽  
Noncanonical Amino Acid

Photosynthetic reaction centers (RCs) from Rhodobacter sphaeroides were engineered to vary the electronic properties of a key tyrosine (M210) close to an essential electron transfer component via its replacement with site-specific, genetically encoded noncanonical amino acid tyrosine analogs. High fidelity of noncanonical amino acid incorporation was verified with mass spectrometry and X-ray crystallography and demonstrated that RC variants exhibit no significant structural alterations relative to wild type (WT). Ultrafast transient absorption spectroscopy indicates the excited primary electron donor, P*, decays via a ∼4-ps and a ∼20-ps population to produce the charge-separated state P+HA− in all variants. Global analysis indicates that in the ∼4-ps population, P+HA− forms through a two-step process, P*→ P+BA−→ P+HA−, while in the ∼20-ps population, it forms via a one-step P* → P+HA− superexchange mechanism. The percentage of the P* population that decays via the superexchange route varies from ∼25 to ∼45% among variants, while in WT, this percentage is ∼15%. Increases in the P* population that decays via superexchange correlate with increases in the free energy of the P+BA− intermediate caused by a given M210 tyrosine analog. This was experimentally estimated through resonance Stark spectroscopy, redox titrations, and near-infrared absorption measurements. As the most energetically perturbative variant, 3-nitrotyrosine at M210 creates an ∼110-meV increase in the free energy of P+BA− along with a dramatic diminution of the 1,030-nm transient absorption band indicative of P+BA– formation. Collectively, this work indicates the tyrosine at M210 tunes the mechanism of primary electron transfer in the RC.

Photosynthetic Reaction Center Variants Made via Genetic Code Expansion Show Tyr at M210 Tunes the Initial Electron Transfer Mechanism

2021 ◽  
Author(s):  
Jared Weaver ◽  
Chi-Yun Lin ◽  
Kaitlyn M. Faries ◽  
Irimpan Mathews ◽  
Silvia Russi ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Free Energy ◽  
Amino Acid ◽  
Near Infrared ◽  
Transient Absorption ◽  
Global Analysis ◽  
Primary Electron ◽  
Wild Type ◽  
Electron Transfer Mechanism ◽  
Noncanonical Amino Acid

Photosynthetic reaction centers (RCs) from Rhodobacter sphaeroides were engineered to vary the electronic properties of a key tyrosine close to an essential electron transfer component (M210) via its replacement with site-specific genetically encoded noncanonical amino acid tyrosine analogs. High fidelity of noncanonical amino acid incorporation was verified with mass spectrometry and x-ray crystallography and demonstrated that RC variants exhibit no significant structural alterations relative to wild-type. Ultrafast transient absorption spectroscopy indicates the excited primary electron donor, P*, decays via an approximately 4 ps and 20 ps population to produce the charge-separated state P+HA- in all variants. Global analysis indicates that in the 4 ps population P+HA- forms through a 2-step process P* –> P+BA– –> P+HA-, while in the 20 ps population it forms via a 1-step P* –> P+HA– superexchange mechanism. The percentage of P* population that decays via the superexchange route varies from approximately 25% to 45% among variants while in wild-type this percentage is approximately 15%. Increases in the P* population which decays via superexchange correlates with increases in free energy of the P+BA– intermediate caused by a given M210 tyrosine analog. This was experimentally estimated through resonance Stark spectroscopy, redox titrations, and near-infrared absorption measurements. As the most energetically perturbative variant, 3-nitrotyrosine at M210 creates an approximately 110 meV increase in the free energy of P+BA– along with a dramatic diminution of the 1030 nm transient absorption band indicative of P+BA– formation. Collectively this work indicates the tyrosine at M210 tunes the mechanism of primary electron transfer in the RC.<br>

Photosynthetic Reaction Center Variants Made via Genetic Code Expansion Show Tyr at M210 Tunes the Initial Electron Transfer Mechanism

2021 ◽  
Author(s):  
Jared Weaver ◽  
Chi-Yun Lin ◽  
Kaitlyn M. Faries ◽  
Irimpan Mathews ◽  
Silvia Russi ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Free Energy ◽  
Amino Acid ◽  
Near Infrared ◽  
Transient Absorption ◽  
Global Analysis ◽  
Primary Electron ◽  
Wild Type ◽  
Electron Transfer Mechanism ◽  
Noncanonical Amino Acid

Photosynthetic reaction centers (RCs) from Rhodobacter sphaeroides were engineered to vary the electronic properties of a key tyrosine close to an essential electron transfer component (M210) via its replacement with site-specific genetically encoded noncanonical amino acid tyrosine analogs. High fidelity of noncanonical amino acid incorporation was verified with mass spectrometry and x-ray crystallography and demonstrated that RC variants exhibit no significant structural alterations relative to wild-type. Ultrafast transient absorption spectroscopy indicates the excited primary electron donor, P*, decays via an approximately 4 ps and 20 ps population to produce the charge-separated state P+HA- in all variants. Global analysis indicates that in the 4 ps population P+HA- forms through a 2-step process P* –> P+BA– –> P+HA-, while in the 20 ps population it forms via a 1-step P* –> P+HA– superexchange mechanism. The percentage of P* population that decays via the superexchange route varies from approximately 25% to 45% among variants while in wild-type this percentage is approximately 15%. Increases in the P* population which decays via superexchange correlates with increases in free energy of the P+BA– intermediate caused by a given M210 tyrosine analog. This was experimentally estimated through resonance Stark spectroscopy, redox titrations, and near-infrared absorption measurements. As the most energetically perturbative variant, 3-nitrotyrosine at M210 creates an approximately 110 meV increase in the free energy of P+BA– along with a dramatic diminution of the 1030 nm transient absorption band indicative of P+BA– formation. Collectively this work indicates the tyrosine at M210 tunes the mechanism of primary electron transfer in the RC.<br>

scholarly journals Photosynthetic Reaction Center Variants Made via Genetic Code Expansion Show Tyr at M210 Tunes the Initial Electron Transfer Mechanism

2021 ◽  
Author(s):  
Jared Weaver ◽  
Chi-Yun Lin ◽  
Kaitlyn M. Faries ◽  
Irimpan Mathews ◽  
Silvia Russi ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Free Energy ◽  
Amino Acid ◽  
Near Infrared ◽  
Transient Absorption ◽  
Global Analysis ◽  
Primary Electron ◽  
Wild Type ◽  
Electron Transfer Mechanism ◽  
Noncanonical Amino Acid

Photosynthetic reaction centers (RCs) from Rhodobacter sphaeroides were engineered to vary the electronic properties of a key tyrosine close to an essential electron transfer component (M210) via its replacement with site-specific genetically encoded noncanonical amino acid tyrosine analogs. High fidelity of noncanonical amino acid incorporation was verified with mass spectrometry and x-ray crystallography and demonstrated that RC variants exhibit no significant structural alterations relative to wild-type. Ultrafast transient absorption spectroscopy indicates the excited primary electron donor, P*, decays via an approximately 4 ps and 20 ps population to produce the charge-separated state P+HA- in all variants. Global analysis indicates that in the 4 ps population P+HA- forms through a 2-step process P* –> P+BA– –> P+HA-, while in the 20 ps population it forms via a 1-step P* –> P+HA– superexchange mechanism. The percentage of P* population that decays via the superexchange route varies from approximately 25% to 45% among variants while in wild-type this percentage is approximately 15%. Increases in the P* population which decays via superexchange correlates with increases in free energy of the P+BA– intermediate caused by a given M210 tyrosine analog. This was experimentally estimated through resonance Stark spectroscopy, redox titrations, and near-infrared absorption measurements. As the most energetically perturbative variant, 3-nitrotyrosine at M210 creates an approximately 110 meV increase in the free energy of P+BA– along with a dramatic diminution of the 1030 nm transient absorption band indicative of P+BA– formation. Collectively this work indicates the tyrosine at M210 tunes the mechanism of primary electron transfer in the RC.

Photoinduced electron transfer dynamics in dye-sensitized ZnO nanowire photoanodes

2018 ◽  
Vol 32 (19) ◽  
pp. 1840049
Author(s):  
Akihiro Furube ◽  
Takahiro Arai ◽  
Masahiro Okazaki ◽  
Shinichiro Yanagiya ◽  
Liang-Yih Chen ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Transient Absorption ◽  
Low Cost ◽  
Transient Absorption Spectroscopy ◽  
Zno Nanowire ◽  
Dye Sensitized ◽  
Femtosecond Transient Absorption ◽  
State Formula ◽  
Flexible Solar Cell

A photoanode using dye-sensitized ZnO nanowire (NW) is a good candidate for low-cost, colorful, light-weight and flexible solar cell material. We have synthesized a ZnO NW anode and a ZnO nanowire–nanoparticle (NWNP) anode, in which ZnO nanoparticles (NPs) are decollated on the surface of NWs. Photo-induced electron transfer dynamics from the excited state of sensitizer dye (D149) to the conduction band of ZnO NW and ZnO NWNP was clarified using femtosecond transient absorption spectroscopy. The decay of the single excited state ([Formula: see text]) of D149 was faster in ZnO NW than that of ZnO NWNP, indicating that NW is more suitable as an efficient electron acceptor.

Transient Absorption Spectroscopy of the Electron Transfer Step in the Photochemically Activated Polymerizations of N-ethylcarbazole and 9-phenylcarbazole.

2021 ◽  
Author(s):  
Georgia Thornton ◽  
Ryan Phelps ◽  
Andrew Orr-Ewing
Keyword(s):  
Electron Transfer ◽  
Radical Cation ◽  
Absorption Spectroscopy ◽  
Electron Acceptor ◽  
Transient Absorption ◽  
Transient Absorption Spectroscopy ◽  
Transfer Step

The polymerization of photoexcited N-ethylcarbazole (N-EC) in the presence of an electron acceptor begins with an electron transfer (ET) step to generate a radical cation of N-EC (N-EC+.). Here, the...

scholarly journals Tracking dissociation dynamics of strong-field ionized 1,2-dibromoethane with femtosecond XUV transient absorption spectroscopy

2016 ◽  
Vol 18 (21) ◽  
pp. 14644-14653 ◽  
Author(s):  
Adam S. Chatterley ◽  
Florian Lackner ◽  
Daniel M. Neumark ◽  
Stephen R. Leone ◽  
Oliver Gessner
Keyword(s):  
Absorption Spectroscopy ◽  
Near Infrared ◽  
Transient Absorption ◽  
Extreme Ultraviolet ◽  
Strong Field ◽  
Transient Absorption Spectroscopy ◽  
Time Resolved ◽  
Strong Field Ionization ◽  
Dissociation Dynamics ◽  
Ultraviolet Absorption Spectroscopy

Using femtosecond time-resolved extreme ultraviolet absorption spectroscopy, the dissociation dynamics of the haloalkane 1,2-dibromoethane (DBE) have been explored following strong field ionization by femtosecond near infrared pulses at intensities between 7.5 × 1013 and 2.2 × 1014 W cm−2.

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