JOURNAL ARTICLE

Pigment organization and energy level structure in light-harvesting complex 4: insights from two-dimensional electronic spectroscopy

Elizabeth L Read, Gabriela S Schlau-Cohen, Gregory S Engel, Toni Georgiou, Miroslav Z Papiz, Graham R Fleming
Journal of Physical Chemistry. B 2009 May 7, 113 (18): 6495-504
19402730
Photosynthetic light-harvesting antennae direct energy collected from sunlight to reaction centers with remarkable efficiency and rapidity. Despite their common function, the pigment-protein complexes that make up antenna systems in different types of photosynthetic organisms exhibit a wide variety of structural forms. Some individual organisms express different types of complexes depending on growth conditions. For example, purple photosynthetic bacteria Rp. palustris preferentially synthesize light-harvesting complex 4 (LH4), a structural variant of the more common and widely studied LH2, when grown under low-light conditions. Here, we investigate the ultrafast dynamics and energy level structure of LH4 using two-dimensional (2D) electronic spectroscopy in combination with theoretical simulations. The experimental data reveal dynamics on two distinct time scales, consistent with coherent dephasing within approximately the first 100 fs, followed by relaxation of population into lower-energy states on a picosecond time scale. We observe excited state absorption (ESA) features marking the existence of high-energy dark states, which suggest that the strongest dipole-dipole coupling in the complex occurs between bacteriochlorophyll transition dipole moments in an in-line geometry. The results help to refine the current understanding of the pigment organization in the LH4 complex, for which a high-resolution crystal structure is not yet available.

Full Text Links

Find Full Text Links for this Article

Discussion

You are not logged in. Sign Up or Log In to join the discussion.

Related Papers

Remove bar
Read by QxMD icon Read
19402730
×

Save your favorite articles in one place with a free QxMD account.

×

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"