skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Comments on the optical lineshape function: Application to transient hole-burned spectra of bacterial reaction centers

; ; ;
Publication Date:
Sponsoring Org.:
OSTI Identifier:
Grant/Contract Number:
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 142; Journal Issue: 9; Related Information: CHORUS Timestamp: 2016-12-28 21:01:32; Journal ID: ISSN 0021-9606
American Institute of Physics
Country of Publication:
United States

Citation Formats

Reppert, Mike, Kell, Adam, Pruitt, Thomas, and Jankowiak, Ryszard. Comments on the optical lineshape function: Application to transient hole-burned spectra of bacterial reaction centers. United States: N. p., 2015. Web. doi:10.1063/1.4913685.
Reppert, Mike, Kell, Adam, Pruitt, Thomas, & Jankowiak, Ryszard. Comments on the optical lineshape function: Application to transient hole-burned spectra of bacterial reaction centers. United States. doi:10.1063/1.4913685.
Reppert, Mike, Kell, Adam, Pruitt, Thomas, and Jankowiak, Ryszard. 2015. "Comments on the optical lineshape function: Application to transient hole-burned spectra of bacterial reaction centers". United States. doi:10.1063/1.4913685.
title = {Comments on the optical lineshape function: Application to transient hole-burned spectra of bacterial reaction centers},
author = {Reppert, Mike and Kell, Adam and Pruitt, Thomas and Jankowiak, Ryszard},
abstractNote = {},
doi = {10.1063/1.4913685},
journal = {Journal of Chemical Physics},
number = 9,
volume = 142,
place = {United States},
year = 2015,
month = 3

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1063/1.4913685

Citation Metrics:
Cited by: 2works
Citation information provided by
Web of Science

Save / Share:
  • The vibrational spectral density is an important physical parameter needed to describe both linear and non-linear spectra of multi-chromophore systems such as photosynthetic complexes. Low-temperature techniques such as hole burning (HB) and fluorescence line narrowing are commonly used to extract the spectral density for a given electronic transition from experimental data. We report here that the lineshape function formula reported by Hayes et al. [J. Phys. Chem. 98, 7337 (1994)] in the mean-phonon approximation and frequently applied to analyzing HB data contains inconsistencies in notation, leading to essentially incorrect expressions in cases of moderate and strong electron-phonon (el-ph) coupling strengths.more » A corrected lineshape function L(ω) is given that retains the computational and intuitive advantages of the expression of Hayes et al. [J. Phys. Chem. 98, 7337 (1994)]. Although the corrected lineshape function could be used in modeling studies of various optical spectra, we suggest that it is better to calculate the lineshape function numerically, without introducing the mean-phonon approximation. New theoretical fits of the P870 and P960 absorption bands and frequency-dependent resonant HB spectra of Rb. sphaeroides and Rps. viridis reaction centers are provided as examples to demonstrate the importance of correct lineshape expressions. Comparison with the previously determined el-ph coupling parameters [Johnson et al., J. Phys. Chem. 94, 5849 (1990); Lyle et al., ibid. 97, 6924 (1993); Reddy et al., ibid. 97, 6934 (1993)] is also provided. The new fits lead to modified el-ph coupling strengths and different frequencies of the special pair marker mode, ω{sub sp}, for Rb. sphaeroides that could be used in the future for more advanced calculations of absorption and HB spectra obtained for various bacterial reaction centers.« less
  • Photochemical hole-burned spectra with improved signal-to-noise ratio ([times]20) are reported for the protonated and deuterated reaction center of the purple bacterium Rhodobacter sphaeroides. Spectra obtained as a function of burn frequency ([omega][sub B]) establish that the lifetime of P870*, the primary electron-donor state, is invariant to location of [omega][sub B] within the inhomogeneous distribution of P870 zero-phonon line transition frequencies. For both the protonated and deuterated RC, which exhibit P870 absorption widths at 4.2 K of only 440 and 420 cm[sup [minus]1], the zero-phonon holes yield a lifetime of 0.93 [+-] 0.10 ps. This lifetime is independent of temperature betweenmore » 1.6 and 8.0 K (range over which the zero-phonon hole could be studied). The invariance of the P870* lifetime to [omega][sub B] and other data indicates that the nonexponential decay of P870* (Vos et al. Proc. Natl. Acad. Sci. U.S.A. 1991, 88, 8885) is due neither to a distribution of values from the electronic coupling matrix element associated with electron transfer, which one might expect from the normal glasslike structural heterogeneity of the RC, nor to gross heterogeneity. The higher quality of the hole spectra has allowed for more stringent testing of the theoretical model previously used to simulate the P870 hole profiles and absorption spectrum. Although the essential findings reported earlier (see, e.g., Reddy et al. Photosyn. Res. 1992, 31, 167) are not altered, it is concluded that the modeling of the distribution of low-frequency phonons (mean frequency approximately 30 cm[sup [minus]1]), which couples to P870*, in terms of a Debye distribution is inadequate. The anomalous low-frequency modes of glasses and polymers are suggested to be important also for proteins. 60 refs., 8 figs., 2 tabs.« less
  • Structured hole-burned spectra for P960 of Rps, viridis are reported which, for appropriate burn wavelengths, exhibit four holes (including a zero-phonon hole). The data indicate that two electronic states contribute significantly to P960 and suggest that the primary electron-transfer step should be modeled in terms of coupled adiabatic trimer states.
  • Reaction centers isolated from three large-scale symmetry mutants, sym0, sym2-1, and sym5-2 described in the previous article of this issue have been investigated by low-temperature ground state and femotosecond-resolution transient absorption spectroscopy. All three of these large-scale symmetry mutants undergo electron transfer at 20 K. The mutants sym0 and sym5-2 have yields and dominant rates of charge separation comparable to wild type. However, the sym2-1 mutant shows a roughly 35% quantum yield at this temperature, and the major kinetic component of the initial electron transfer is slower than wild type by nearly a factor of 100. The sym0 mutant showedmore » substantial changes in the monomer bacteriochlorophyll ground state and transient spectra, and both sym0 and sym2-1 showed changes in the bacteriophenophytin ground state and transient spectra. In particular, sym2-1 shows a small absorbance decrease in the region of the Q{sub x} band of the B side bacteriophenophytin which could be attributed to 10%-20% electron transfer along the B pathway. 54 refs., 5 figs., 1 tab.« less
  • The key reaction of photosynthetic solar energy conversion involves the photoexcitation of a primary donor (P) followed by rapid, sequential electron transfer to a series of acceptors resulting in charge separation. Electron-spin polarized (ESP) EPR spectra at W-band (95 GHz) were obtained for deuterated Fe-removed/Zn-substituted photosynthetic bacterial reaction centers (RCs) to investigate the influence of the rate of charge separation on the observed P{sup +}Q{sub A}{sup {minus}} charge separated state. Temperature dependent ESP EPR spectra for kinetically characterized Zn-substituted RCs from Rb. sphaeroides R-26 having different rates (k{sub Q}) of the electron transfer from the bacteriopheophytin to the quinone acceptormore » were obtained. The Zn-RCs exhibited either the native fast (200 ps){sup {minus}1} k{sub Q} or a slow (3--6 ns){sup {minus}1} k{sub Q} at 298 K as determined from transient optical measurements. Sequential electron-transfer polarization modeling of the polarized W-band EPR spectra obtained with these samples was used to address the reason for the differences in the electron-transfer rates. Here, the authors report the k{sub Q} rate constant, the temperature dependence of k{sub Q}, and the reorganization energy for the P{sup +}H{sup {minus}}Q{sub A} and P{sup +}HQ{sub A}{sup {minus}} electron-transfer step determined from SETP modeling of the experimental spectra. The reorganization energy for the electron-transfer process between P{sup +}H{sup {minus}}Q{sub A} and P{sup +}HQ{sub A}{sup {minus}}, and not structural changes in the donor or acceptor, was found to be the dominant factor that is altered during Fe-removal procedures.« less