Pigment-protein complex

The carotenoids are located in photosynthetic pigment-protein complexes (PPCs) in the thylakoid membranes (Young, 1993), with minor amounts in the chloroplast envelope (Joyard et al, 1991) and the envelope of amyloplasts (Fishwick and Wright, 1980). In all plastid envelope membranes, violaxanthin is the major carotenoid. Carotenes are also found in plastoglobuli (Lichtenthaler and Peveling, 1966). 

In vivo, one of the main groups of carotenoids are the snlfates of eritoxanthin sulfate and of the caloxanthin sulfates. The sulfates of carotenoids are not associated with pigment-protein complexes, for example, they are neither part of the fight harvesting complexes nor of the reaction centers. In nonphotosynthetic bacteria, carotenoids appear sporadically and when present, they have unique characteristics. Some Staphylococci accumulate C30 carotenoids, flavobacteria C45 and C50, while some mycobacteria accumulate C40 carotenoid glycosides. ... 

Renger, T., May, V. and Kuhn, O. (2001). Ultrafast excitation energy dynamics in photosynthetic pigment protein complexes. Phys. Rep. 343, 137-254. 

Unlike the photosynthetic apparatus of photosynthetic bacteria, that of cyanobacteria consits of two photosystems, PS I and II, connected by an electron transport chain. The only chlorophyll present is chlorophyll a, and, therefore, chlorophylls b—d are not of interest in this article. Chlorophyll a is the principal constituent of PS I. Twenty per cent of isolated pigment-protein complexes contain one P700 per 20—30 chlorophyll a molecules the other 80% contain only chlorophyll a20). The physical and chemical properties of chlorophyll a and its role in photosynthesis have recently been described by Meeks77), Mauzerall75), Hoch60), Butler10), and other authors of the Encyclopedia of Plant Physiology NS Vol. 5. 

Photosystem I is a membrane pigment-protein complex in green plants, algae as well as cyanobacteria, and undergoes redox reactions by using the electrons transferred from photosystem II (PS II) [1], These membrane proteins are considered to be especially interesting in the study of monomolecular assemblies, because their structure contains hydrophilic area that can interact with the subphase as well as hydrophobic domains that can interact either with each other or with detergent and lipids [2], Moreover, studies with such proteins directly at the air-water interface are expected to be a valuable approach for their two-dimensional crystallization. 

Pullerits T. and Sundstrom V. (1996) Photosynthetic Light-Harvesting Pigment-Protein Complexes Toward Understanding How and Why, Acc. Chem. Res. 29, 381-389. 

It is intended in the present review to critically summarize current knowledge concerning structure and function of the pigment-protein complexes of higher plant photosystems. 

The CP26 pigment-protein complex has been described in maize and spinach as having an intermediate chib content between CP29 and LHCII [8, 75,76]. Its pigment complement includes violaxanthin, lutein and neoxanthin as well as chla and chib in a 2.2 ratio [10]. Lower (1.8) and higher (2.7) a/b ratio... 

Reaction centers from photosynthetic organisms are specialized pigment-protein complexes in which photon energy is converted into chemical energy ( ) This is accomplished by a series of rapid electron transfer reactions that produce a spacially-separated oxidized donor and a reduced electron acceptor 2). Reaction centers from the purple photosynthetic bacterium Rhodopseudomonas sphaeroides contain four molecules of bacteriochlorophyll (BChl), two of bac-teriopheophytin (BPh), one tightly-bound or primary ubiquinone (Q), a... 

A. Imaging Aggregates oe the Green Plant Light-Harvesting Pigment-Protein Complex LHCM... 

FIGURE 4.5 Aggregates of light-harvesting pigment-protein complex (LHCll) imaged with (a) MPF, (h) SHG, and (c) THG contrasts. The scale har is 3 pm. 

Fast excited-state reaction in the photoreceptor pigment-protein complex of the ciliate Blepharisma japonicum... 

Biological systems Ligand-myoglobin Protein dynamics Bacteriorhodopsin Light harvesting Pigment-protein complexes Photosynthetic reaction centers... 

Two experimental systems will be briefly described to illustrate some of the ideas presented in the previous section. The examples span the range of system complexity from a diatomic molecule (I2) [28] to a supramolec-ular pigment-protein complex (the core light-harvesting antenna of photosynthetic bacteria, LH1 [18, 19]). 

Cover concept by eStudio Calamar Steinen using a background picture from The Protein Databank (1 Kzu). Courtesy of Dr. Antoine M. van Oijen, Department of Molecular Physics, Huygens Laboratory, Leiden University, The Netherlands. Reprinted with permission from Science 285 (1999) 400-402 ("Unraveling the Electronic Structure of Individual Photosynthetic Pigment-Protein Complexes", by A. M. van Oijen et al.) Copyright 1999, American Association for the Advancement of Science. 

Photosynthetic membranes also contain pigment-protein complexes that serve as antennas. When the antenna absorbs a photon, energy hops rapidly from complex to complex by resonance energy transfer until it is trapped in a reaction center. 

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