B side electron transfer in a rhodobacter sphaeroides reaction center mutant in which the B side monomer bacteriochlorophyll is replaced with bacteriopheophytin: Low-temperature study and energetics of charge-separated states

Evaldas Katilius, Zivile Katiliene, Su Lin, Aileen K W Taguchi, Neal Woodbury

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Abstract

The mutation, HL(M182), in the Rhodobacter sphaeroides reaction center (RC) results in the replacement of the monomer bacteriochlorophyll (BChl) on the inactive side (B side) of the RC with a bacteriopheophytin (BPheo; the new cofactor is referred to as φB). In φB-containing RCs, the first excited state of the primary donor (P*) decays with an accelerated time constant of 2.6 ± 0.1 ps at room temperature as compared to 3.1 ± 0.2 ps in wild-type (WT) RCs. At low temperatures, P* decay is essentially the same in the HL(M182) mutant and WT RCs: 1.4 ± 0.1 ps at 77 K and 1.1 ± 0.1 ps at 9 K. The yield of the charge-separated P+φB - state decreases from 35% at room temperature to 12% at 77 and 9 K. The decreased P+φB - yield is apparently due to the fact that the rate of the charge separation along the A side of the RC at low temperature increases, while the rate along the B side remains essentially unchanged. From measurements of the long-lived fluorescence decay at room temperature, the standard free energy of the P+φB - state is estimated to be about 0.16 ± 0.04 eV below P*. Given a difference between the midpoint potentials of BChl and BPheo of 0.26 ± 0.03 V, the standard free energy of the P+BB - state in WT RC is estimated to be 0.1 ± 0.07 eV above P*.

Original languageEnglish (US)
Pages (from-to)1471-1475
Number of pages5
JournalJournal of Physical Chemistry B
Volume106
Issue number6
DOIs
StatePublished - Feb 14 2002

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Bacteriochlorophylls
electron transfer
monomers
Monomers
Electrons
decay
room temperature
free energy
Free energy
Temperature
polarization (charge separation)
mutations
time constant
Excited states
fluorescence
Fluorescence
bacteriopheophytin
excitation

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

@article{033875081345435cb2c75e4a1d3b98f5,
title = "B side electron transfer in a rhodobacter sphaeroides reaction center mutant in which the B side monomer bacteriochlorophyll is replaced with bacteriopheophytin: Low-temperature study and energetics of charge-separated states",
abstract = "The mutation, HL(M182), in the Rhodobacter sphaeroides reaction center (RC) results in the replacement of the monomer bacteriochlorophyll (BChl) on the inactive side (B side) of the RC with a bacteriopheophytin (BPheo; the new cofactor is referred to as φB). In φB-containing RCs, the first excited state of the primary donor (P*) decays with an accelerated time constant of 2.6 ± 0.1 ps at room temperature as compared to 3.1 ± 0.2 ps in wild-type (WT) RCs. At low temperatures, P* decay is essentially the same in the HL(M182) mutant and WT RCs: 1.4 ± 0.1 ps at 77 K and 1.1 ± 0.1 ps at 9 K. The yield of the charge-separated P+φB - state decreases from 35{\%} at room temperature to 12{\%} at 77 and 9 K. The decreased P+φB - yield is apparently due to the fact that the rate of the charge separation along the A side of the RC at low temperature increases, while the rate along the B side remains essentially unchanged. From measurements of the long-lived fluorescence decay at room temperature, the standard free energy of the P+φB - state is estimated to be about 0.16 ± 0.04 eV below P*. Given a difference between the midpoint potentials of BChl and BPheo of 0.26 ± 0.03 V, the standard free energy of the P+BB - state in WT RC is estimated to be 0.1 ± 0.07 eV above P*.",
author = "Evaldas Katilius and Zivile Katiliene and Su Lin and Taguchi, {Aileen K W} and Neal Woodbury",
year = "2002",
month = "2",
day = "14",
doi = "10.1021/jp013265o",
language = "English (US)",
volume = "106",
pages = "1471--1475",
journal = "Journal of Physical Chemistry B Materials",
issn = "1520-6106",
publisher = "American Chemical Society",
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TY - JOUR

T1 - B side electron transfer in a rhodobacter sphaeroides reaction center mutant in which the B side monomer bacteriochlorophyll is replaced with bacteriopheophytin

T2 - Low-temperature study and energetics of charge-separated states

AU - Katilius, Evaldas

AU - Katiliene, Zivile

AU - Lin, Su

AU - Taguchi, Aileen K W

AU - Woodbury, Neal

PY - 2002/2/14

Y1 - 2002/2/14

N2 - The mutation, HL(M182), in the Rhodobacter sphaeroides reaction center (RC) results in the replacement of the monomer bacteriochlorophyll (BChl) on the inactive side (B side) of the RC with a bacteriopheophytin (BPheo; the new cofactor is referred to as φB). In φB-containing RCs, the first excited state of the primary donor (P*) decays with an accelerated time constant of 2.6 ± 0.1 ps at room temperature as compared to 3.1 ± 0.2 ps in wild-type (WT) RCs. At low temperatures, P* decay is essentially the same in the HL(M182) mutant and WT RCs: 1.4 ± 0.1 ps at 77 K and 1.1 ± 0.1 ps at 9 K. The yield of the charge-separated P+φB - state decreases from 35% at room temperature to 12% at 77 and 9 K. The decreased P+φB - yield is apparently due to the fact that the rate of the charge separation along the A side of the RC at low temperature increases, while the rate along the B side remains essentially unchanged. From measurements of the long-lived fluorescence decay at room temperature, the standard free energy of the P+φB - state is estimated to be about 0.16 ± 0.04 eV below P*. Given a difference between the midpoint potentials of BChl and BPheo of 0.26 ± 0.03 V, the standard free energy of the P+BB - state in WT RC is estimated to be 0.1 ± 0.07 eV above P*.

AB - The mutation, HL(M182), in the Rhodobacter sphaeroides reaction center (RC) results in the replacement of the monomer bacteriochlorophyll (BChl) on the inactive side (B side) of the RC with a bacteriopheophytin (BPheo; the new cofactor is referred to as φB). In φB-containing RCs, the first excited state of the primary donor (P*) decays with an accelerated time constant of 2.6 ± 0.1 ps at room temperature as compared to 3.1 ± 0.2 ps in wild-type (WT) RCs. At low temperatures, P* decay is essentially the same in the HL(M182) mutant and WT RCs: 1.4 ± 0.1 ps at 77 K and 1.1 ± 0.1 ps at 9 K. The yield of the charge-separated P+φB - state decreases from 35% at room temperature to 12% at 77 and 9 K. The decreased P+φB - yield is apparently due to the fact that the rate of the charge separation along the A side of the RC at low temperature increases, while the rate along the B side remains essentially unchanged. From measurements of the long-lived fluorescence decay at room temperature, the standard free energy of the P+φB - state is estimated to be about 0.16 ± 0.04 eV below P*. Given a difference between the midpoint potentials of BChl and BPheo of 0.26 ± 0.03 V, the standard free energy of the P+BB - state in WT RC is estimated to be 0.1 ± 0.07 eV above P*.

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U2 - 10.1021/jp013265o

DO - 10.1021/jp013265o

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JF - Journal of Physical Chemistry B Materials

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IS - 6

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