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15 - Perspectives on future directions
- Edited by Suzanne Roy, Carole A. Llewellyn, Plymouth Marine Laboratory, Einar Skarstad Egeland, Geir Johnsen, Norwegian University of Science and Technology, Trondheim
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- Phytoplankton Pigments
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- 05 March 2012
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- 27 October 2011, pp 609-624
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Summary
Introduction
‘We are on the verge of a golden age.’
(Quote by Martin Lohr on xanthophyll research)This chapter presents a diverse collection of perspectives covering recent discoveries and ‘crystal ball gazing’ on future directions. Detection and characterisation from a molecular level is covered through to monitoring phytoplankton dynamics and climate change at a regional and global Earth observation level. At a molecular level, perspectives are provided on our basic understanding of the role of pigments in photosynthesis and photoprotection incorporating the development of new analytical and ‘omics’ techniques. Applied perspectives are included on HAB detection, aquaculture and algal biotechnology. Phytoplankton pigment research continues to develop opening up many fascinating and exciting possibilities. These perspectives highlight how research on pigments acts as a linchpin across a diverse range of disciplines including microbial ecology, oceanography, limnology, remote sensing and applied phycology.
2 - Recent advances in chlorophyll and bacteriochlorophyll biosynthesis
- Edited by Suzanne Roy, Carole A. Llewellyn, Plymouth Marine Laboratory, Einar Skarstad Egeland, Geir Johnsen, Norwegian University of Science and Technology, Trondheim
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- Phytoplankton Pigments
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- 05 March 2012
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- 27 October 2011, pp 78-112
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Summary
Introduction
In 1997, the first edition of Phytoplankton Pigments in Oceanography was published (Jeffrey et al., 1997) in which a chapter was presented by Porra et al. (1997) on photosynthetic pigments, namely, chlorophylls (Chls), phycobilins and carotenoids. In this current volume, the phycobilins and carotenoids are discussed elsewhere (Chapters 9 and 3, this volume). The earlier presentation (Porra et al., 1997) only briefly described the Chl biosynthetic pathway while addressing the functions and locations of Chls in protein complexes of both the light-harvesting antenna complexes and reaction centres of the two photosystems present in the chloroplasts of higher plants and green algae. A comprehensive survey of Chl biodegradation was also described in the earlier presentation (Porra et al., 1997) but more recent information is now available (Kräutler and Hörtensteiner, 2006). In this current chapter, a more comprehensive account of the Chl biosynthetic pathway is presented together with the structures of many of the naturally occurring Chls, with a special focus on recently discovered Chls and their possible syntheses.
Structures of chlorophylls
The structures and properties of naturally occurring Chls have been extensively reviewed (Scheer, 1991, 2003, 2006). The Chls are mostly magnesium coordination complexes, but also rarely Zn-coordination complexes (see Sections 2.2.3 and 2.4.10.3), of cyclic tetrapyrroles which contain a fifth isocyclic (cyclopentanone) ring E constructed enzymically from the 13-propionate side chain of Mg-protoporphyrin IX (see Section 2.4.3): for the IUPAC-IUB tetrapyrrole atom numbering and ring labelling systems, see Figure 2.1B. All Chls possess a 131-oxo group and mostly, but not always, a 132 methylcarboxylate substituent while the 17-propionate side chain is usually, but not always, esterified with a long-chain isoprenoid alcohol such as phytol, farnesol or geranyl-geraniol.
9 - Phycobiliproteins
- Edited by Suzanne Roy, Carole A. Llewellyn, Plymouth Marine Laboratory, Einar Skarstad Egeland, Geir Johnsen, Norwegian University of Science and Technology, Trondheim
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- Phytoplankton Pigments
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- 05 March 2012
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- 27 October 2011, pp 375-411
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Introduction
Phycobiliproteins are the major light-harvesting pigments of cyanobacteria, red algae, glaucocystophytes (cyanelles) and cryptophytes (MacColl and Guard-Friar, 1987; Sidler, 1994). They are characterized by linear tetrapyrrolic chromophores, known as bilins, that are covalently bound to cysteines of the apoproteins via thioether bonds, and they harvest light for photosynthesis efficiently in the ‘green gap’ where chlorophylls absorb only poorly (Sidler, 1994). Unlike isolated chlorophyll chromophores, free bilins are photophysically unsuited as photoreceptors: they absorb light only poorly and their excited states are very short lived, thereby leading to rapid conversion of excitation energy to heat (Scheer, 1982; Braslavsky et al., 1983; Falk, 1989). These properties also prevail in denatured biliproteins. The photophysical properties of native biliproteins are, by contrast, much more favourable: the light absorption of the chromophores is increased by almost one order of magnitude and the excited lifetimes by four orders of magnitude, which, in combination, render them excellent photoreceptors. The absorption of individual chromophores can, moreover, be shifted by almost 100 nm, and also the circular dichroism of biliproteins is modulated drastically during folding (see Scheer, 2003 and Kupka and Scheer, 2008 for leading references). The underlying nature of these molecular adaptations, which are still only partly understood, consists mainly of extensive chromophore protein interactions by which the chromophore conformation and dynamics are modulated. Covalent binding to the apoproteins appears to be important in assisting these interactions. Although cysteine mutants indicate that covalent binding is not absolutely necessary for function (Gindt et al., 1994; Jorissen et al., 2002; Inomata et al., 2006), it does assist functional optimization (Gindt et al., 1994) because it stabilizes both the labile chromophores (Scheer, 1982) and proteins (Anderson and Toole, 1998; Shen et al., 2008a, b). In cyanobacteria and red algae, up to four bilin chromophores are post-translationally attached, via thioether bonds, to specific cysteines of up to a dozen or even more individual proteins (Sidler, 1994); further, an additional modification in β-subunits is the methylation of a conserved asparagine-72 (Swanson and Glazer, 1990; Schluchter et al., 2010). Chromophore attachment also appears to be a pre-requisite for the assembly of phycobilisomes (PBS) (Anderson and Toole, 1998) which are the light-harvesting antennae of blue-green algae and of both red and cryptophyte algae.
Metal-Enhanced Fluorescence of Chlorophylls in Single Light-Harvesting Complexes
- Sebastian Mackowski, Dawid Piatkowski, Stephan Wörmke, Achim Hartschuh, Christoph Bräeuchle, Tatas H. P. Brotosudarmo, Hugo Scheer, Ashish Agarwal, Nicholas A. Kotov, Alexander O Govorov
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- MRS Online Proceedings Library Archive / Volume 1208 / 2009
- Published online by Cambridge University Press:
- 31 January 2011, 1208-O14-01
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- 2009
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We show that the fluorescence of peridinin-chlorophyll a-protein complexes can be strongly enhanced via coupling with plasmon excitations localized in metal nanostructures. The results of ensemble and single-molecule spectroscopy experiments at room temperature demonstrate six-fold increase of the emission intensity of the light-harvesting complex when it is placed in the vicinity of chemically prepared silver islands. Irrespective of the enhancement, we observe no effect of the metal nanoparticle on the fluorescence emission energy of the complex. This observation implies that plasmon excitations may be applied for controlling the optical properties of complex biomolecules.