B896 and B870 components of the rhodobacter sphaeroides antenna: A hole burning study

Journal Article · Thu Jul 23 04:00:00 EDT 1992 · Journal of Physical Chemistry

DOI:https://doi.org/10.1021/j100194a065· OSTI ID:554929

Reddy, N R.S.; Small, G J ^[1]; Picorel, R ^[2]

---

1. Iowa State Univ., Ames, IA (United States)
2. E.E. Aula Dei, CSIC, Zaragoza (Spain)

Novel nonphotochemical hole burning action spectra are presented that yield the low-temperature absorption profiles of B896 and B870 and their underlying structures (linear electron-phonon coupling and site inhomogeneous broadening). The results establish that B896 and B870 are associated with the far more intense B875 and B850 bacteriochlorophyll {alpha} absorption bands, respectively, of the light harvesting I and II complexes. The homogeneous widths of the B896 and B870 zero-phonon holes are the same within experimental uncertainty, 3.2 cm{sup {minus}1} at 4.2 K, which corresponds to a total optical dephasing time of 6.6 ps. A number of interpretations for B870 and B896 are considered. Favored is one in which they are due to the lowest energy levels of the B850* and B875* exciton bands (asterisk denoting the S{sub 1}(Q{sub y}) state). Based on studies of the dephasing of excitons in organic crystals, the 6.6-ps dephasing of B896* is attributed to exciton scattering with energetic inequivalent neighboring unit cells. Such scattering and B870 to B875 energy transfer are suggested to be contributors to the dephasing of B870*. The effect of glasslike structural heterogeneity on the optical selection rules for unit cells of cyclic symmetry is also considered. 71 refs., 5 figs.

• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 554929
• Journal Information: Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 15 Vol. 96; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
CHLOROPHYLL-BINDING PROTEINS
COMPLEXES
ELECTRON-PHONON COUPLING
ENERGY TRANSFER
PHOTOSYNTHESIS