Abstract
Spectral and kinetic information on energy transfer within the light-harvesting complex II (LHCII) monomer was obtained from this subpicosecond transient absorption study, by using selective excitation (663, 669, 672, 678, and 682 nm) of various Chl a absorption bands and detecting the induced changes over the entire Qy region (650-700 nm). It is shown that transfer from the pigment(s) absorbing around 663 nm to the low energy ones occurs in 5 +/- 1 ps, whereas the 670-nm excitation is delivered to the same "destination" in two phases (0.30 +/- 0.05 ps, and 12 +/- 2 ps), and a fast equilibration (lifetime 0.45 +/- 0.05 ps) takes place within the main absorption band (675-680 nm). From comparison with results from similar time-resolved measurements on trimeric samples, it can be concluded that the intramonomeric energy transfer completely determines the spectral equilibration observed in native LHCII complexes. To correlate the measured lifetimes and their associated spectra with the pigment organization within the available structural model of LHCII (. Nature. 367:614-621), extensive but straightforward theoretical modeling was used. Thus it is demonstrated that the pigment assignment (Chl a or Chl b) given by Kuhlbrandt and co-workers cannot simultaneously describe the dichroic spectra and the transient absorption results for the rather homologous LHCII and CP29 proteins. A more recent assignment for CP29, in which a Chl b molecule ("Chl b5") is identified as a Chl a (Dr. R. Bassi, personal communication), leads to a much better description of both CP29 and LHCII. Furthermore, the orientations of the transition dipole moments, which have not been obtained in the crystal structure, are now assigned for most of the Chl's.
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- Connelly J. P., Müller M. G., Bassi R., Croce R., Holzwarth A. R. Femtosecond transient absorption study of carotenoid to chlorophyll energy transfer in the light-harvesting complex II of photosystem II. Biochemistry. 1997 Jan 14;36(2):281–287. doi: 10.1021/bi962467l. [DOI] [PubMed] [Google Scholar]
- Gradinaru C. C., Pascal A. A., van Mourik F., Robert B., Horton P., van Grondelle R., van Amerongen H. Ultrafast evolution of the excited states in the chlorophyll a/b complex CP29 from green plants studied by energy-selective pump-probe spectroscopy. Biochemistry. 1998 Jan 27;37(4):1143–1149. doi: 10.1021/bi9722655. [DOI] [PubMed] [Google Scholar]
- Kim J., Blackshear P. J., Johnson J. D., McLaughlin S. Phosphorylation reverses the membrane association of peptides that correspond to the basic domains of MARCKS and neuromodulin. Biophys J. 1994 Jul;67(1):227–237. doi: 10.1016/S0006-3495(94)80473-4. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kühlbrandt W., Wang D. N., Fujiyoshi Y. Atomic model of plant light-harvesting complex by electron crystallography. Nature. 1994 Feb 17;367(6464):614–621. doi: 10.1038/367614a0. [DOI] [PubMed] [Google Scholar]
- Moog R. S., Kuki A., Fayer M. D., Boxer S. G. Excitation transport and trapping in a synthetic chlorophyllide substituted hemoglobin: orientation of the chlorophyll S1 transition dipole. Biochemistry. 1984 Mar 27;23(7):1564–1571. doi: 10.1021/bi00302a034. [DOI] [PubMed] [Google Scholar]
- Nussberger S., Dekker J. P., Kühlbrandt W., van Bolhuis B. M., van Grondelle R., van Amerongen H. Spectroscopic characterization of three different monomeric forms of the main chlorophyll a/b binding protein from chloroplast membranes. Biochemistry. 1994 Dec 13;33(49):14775–14783. doi: 10.1021/bi00253a016. [DOI] [PubMed] [Google Scholar]
- Peterman E. J., Dukker F. M., van Grondelle R., van Amerongen H. Chlorophyll a and carotenoid triplet states in light-harvesting complex II of higher plants. Biophys J. 1995 Dec;69(6):2670–2678. doi: 10.1016/S0006-3495(95)80138-4. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Peterman E. J., Gradinaru C. C., Calkoen F., Borst J. C., van Grondelle R., van Amerongen H. Xanthophylls in light-harvesting complex II of higher plants: light harvesting and triplet quenching. Biochemistry. 1997 Oct 7;36(40):12208–12215. doi: 10.1021/bi9711689. [DOI] [PubMed] [Google Scholar]
- Savikhin S., van Amerongen H., Kwa S. L., van Grondelle R., Struve W. S. Low-temperature energy transfer in LHC-II trimers from the Chl a/b light-harvesting antenna of photosystem II. Biophys J. 1994 May;66(5):1597–1603. doi: 10.1016/S0006-3495(94)80951-8. [DOI] [PMC free article] [PubMed] [Google Scholar]