Q{sub y}-level structure and dynamics of solubilized light-harvesting complex 2 of green plants: Pressure and hole burning studies
- Humboldt Univ., Berlin (Germany). Inst. of Physics
- Ames Lab., IA (United States)
- Technical Univ., Berlin (Germany). Max-Volmer Inst.
Nonphotochemical hole burning and pressure-dependent absorption and hole-burning results are presented for the isolated (disaggregated) chlorophyll a/b light-harvesting 2 trimer antenna complex of green plants. Analysis of the 4.2 K burn-fluence dependent hole spectra and zero-phonon hole action spectra indicates that the three lowest energy states (Q{sub y}) lie at 67.1, 678.4 and 679.8 nm. Their combined absorption intensity is equivalent to that of three Chl a molecules. The inhomogeneous broadening of their absorption bands is 70 cm{sup {minus}1}. It is argued that these states, separated by 30 cm{sup {minus}1}, are associated with the lowest energy state of the trimer subunit with the 30 cm{sup {minus}1} separations due to the indigenous structural heterogeneity of protein complexes. The linear electron-phonon coupling of the 679.8 nm state is weak and characterized, in part, by a mean phonon frequency of {omega}{sub m} = 18 cm{sup {minus}1} and Huang-Rhys factor of S{sub m} = 0.8, values which yield the correct Stokes shift for fluorescence from the 679.8 nm state at 4.2 K.The temperature dependence of the zero-phonon hole (ZPH) width for that state is consistent with optical dynamics due to coupling with glasslike two-level systems of the protein. The ZPH width at 1.9 K is 0.037 cm{sup {minus}1}. Satellite hole structure produced by burning in the above three states as well as their low linear pressures shift rates indicate that the Chl a molecule of the subunit associated with them is weakly coupled to other Chl molecules. The linear pressure shift rates for the main Q{sub y}-absorption bands are also low.
- Sponsoring Organization:
- USDOE, Washington, DC (United States); Deutscher Akademischer Austauschdienst, Bonn (Germany); Deutsche Forschungsgemeinschaft, Bonn (Germany)
- DOE Contract Number:
- W-7405-ENG-82
- OSTI ID:
- 338459
- Journal Information:
- Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Journal Name: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory Journal Issue: 14 Vol. 103; ISSN 1089-5639; ISSN JPCAFH
- Country of Publication:
- United States
- Language:
- English
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