Target Analysis of the Bacteriorhodopsin Photocycle Using a Spectrotemporal Model

Stokkum, Ivo H. M. van; Lozier, Richard H.

doi:10.1021/jp0127723

Cited by 45 publications

(88 citation statements)

References 68 publications

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“…PR and BR photocycle kinetics can be described by sequential reaction schemes . Photocycle intermediates of PR are often termed in analogy to the BR photocycle intermediates K, L, M, N and O (some intermediate substates postulated in literature are not listed ).…”

Section: Resultsmentioning

confidence: 99%

Proteorhodopsin Photocycle Kinetics Between pH 5 and pH 9

Köhler

Weber

Glaubitz

et al. 2017

Photochem & Photobiology

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The retinal protein proteorhodopsin is a homolog of the well-characterized light-driven proton pump bacteriorhodopsin. Basic mechanisms of proton transport seem to be conserved, but there are noticeable differences in the pH ranges of proton transport. Proton transport and protonation state of a carboxylic acid side chain, the primary proton acceptor, are correlated. In case of proteorhodopsin, the pK of the primary proton acceptor Asp-97 (pK ≈ 7.5) is unexpectedly close to environmental pH (pH ≈ 8). A significant fraction of proteorhodopsin is possibly inactive at natural pH, in contrast to bacteriorhodopsin. We investigated photoinduced kinetics of proteorhodopsin between pH 5 and pH 9 by time resolved UV/vis absorption spectroscopy. Kinetics is inhomogeneous within that pH region and can be considered as a superposition of two fractions. These fractions are correlated with the Asp-97 titration curve. Beside Asp-97, protonation equilibria of other groups influence kinetics, but the observations do not point toward major differences of primary proton acceptor function in proteorhodopsin and bacteriorhodopsin. The pK of proteorhodopsin and some of its variants is suspected to be an example of molecular adaptation to the physiology of the original organisms.

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Section: Resultsmentioning

confidence: 99%

Proteorhodopsin Photocycle Kinetics Between pH 5 and pH 9

Köhler

Weber

Glaubitz

et al. 2017

Photochem & Photobiology

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“…The energy-transfer rate has been calculated from k ET = 1/tÀ1/t 0 , in which t 0 is the iridium lifetime given by the time-resolved emission measurements, and t is the quenched lifetime obtained from kinetic analysis (30.9 ps). A global fit procedure using TIMP was applied to the data matrix, [25] evaluating all % 300 kinetic traces, resulting in an energy-transfer rate of k ET = 3.24 10 10 s…”

Section: Resultsmentioning

confidence: 99%

Efficient Photoinduced Energy Transfer Mediated by Aromatic Homoconjugated Bridges

Barcina

Herrero-García

Cucinotta

et al. 2010

Chemistry A European J

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A new donor-bridge-acceptor (D-B-A) dyad consisting of ruthenium(II) and iridium(III) species separated by an homoconjugated bridge derived from 7,7-diphenylnorbornane [Ir-Nor-Ru](3+) has been synthesised. The photophysical and electrochemical properties of the heterodinuclear complex have been compared with those of the analogous homodinuclear complexes [Ru-Nor-Ru](4+) and [Ir-Nor- Ir](2+) . Transient absorption spectra on the nanosecond and sub-picosecond timescales show, for the first time, that an homoconjugated bridge can mediate efficiently in the photoinduced energy transfer from the iridium(III) to the ruthenium(II) centres according to a Dexter-type mechanism.

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“…For the initial analysis with a simple sequential model, the program Origin 6.0 (Microcal Software, Inc.) was used. For analysis with more complex models the merged traces were analyzed with a global fitting program described elsewhere , making use of the Target Analysis method (van Stokkum and Lozier, 2002). For the Target Analysis to succeed, several spectral constraints needed to be introduced for the model depicted in Fig.…”

Section: Discussionmentioning

confidence: 99%

Deuterium Isotope Effects in the Photocycle Transitions of the Photoactive Yellow Protein

Hendriks

Stokkum

Hellingwerf

2003

Biophysical Journal

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The Photoactive Yellow Protein (PYP) from Halorhodospira halophila (formerly Ectothiorhodospira halophila) is increasingly used as a model system. As such, a thorough understanding of the photocycle of PYP is essential. In this study we have combined information from pOH- (or pH-) dependence and (kinetic) deuterium isotope effects to elaborate on existing photocycle models. For several characteristics of PYP we were able to make a distinction between pH- and pOH-dependence, a nontrivial distinction when comparing data from samples dissolved in H(2)O and D(2)O. It turns out that most characteristics of PYP are pOH-dependent. We confirmed the existence of a pB' intermediate in the pR to pB transition of the photocycle. In addition, we were able to show that the pR to pB' transition is reversible, which explains the previously observed biexponential character of the pR-to-pB photocycle step. Also, the absorption spectrum of pB' is slightly red-shifted with respect to pB. The recovery of the pG state is accompanied by an inverse kinetic deuterium isotope effect. Our interpretation of this is that before the chromophore can be isomerized, it is deprotonated by a hydroxide ion from solution. From this we propose a new photocycle intermediate, pB(deprot), from which pG is recovered and which is in equilibrium with pB. This is supported in our data through the combination of the observed pOH and pH dependence, together with the kinetic deuterium isotope effect.

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Target Analysis of the Bacteriorhodopsin Photocycle Using a Spectrotemporal Model

Cited by 45 publications

References 68 publications

Proteorhodopsin Photocycle Kinetics Between pH 5 and pH 9

Proteorhodopsin Photocycle Kinetics Between pH 5 and pH 9

Efficient Photoinduced Energy Transfer Mediated by Aromatic Homoconjugated Bridges

Deuterium Isotope Effects in the Photocycle Transitions of the Photoactive Yellow Protein

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